The Kynix Blog

CatalogⅠ IntroductionⅡ Types of sensors in the phone  2.1 Acceleration sensor  2.2 Gravity sensor  2.3 Light sensor  2.4 Proximity sensor  2.5 Magnetism Sensor  2.6 Gyroscope  2.7 GPS position sensor  2.8 Hall Sensor  2.9 Air pressure sensor  2.10 Heart rate sensor  2.11 Blood oxygen sensor  2.12 UV sensor  2.13 Temperature sensor  2.14 Fingerprint sensorⅢ Integrated application of sensors in the phoneⅣ SummaryⅤ FAQⅠ IntroductionThe development speed of smartphone technology is unimaginable, which includes sensor technology. Sensors in mobile phones have the ability to make a big difference in our way of life.Sensors in mobile phones refer to those components that can be sensed by chips, such as response distance, light value, temperature value, brightness value and pressure value. Like all electronic components, these sensors are getting smaller and smaller, with stronger performance and lower cost. Through the various data collected by the sensor, through the analysis and calculation of the program software of the mobile phone, various applications are generated. Today's mobile phones have provided extremely convenient functions in our social, financial payment, sports monitoring, entertainment, learning and other aspects.Ⅱ Types of sensors in the phone2.1 Acceleration sensorThe concept of acceleration sensor and gravity sensor overlap slightly, but in fact, they are different. Acceleration sensor is measured in multiple dimensions, which refers to the acceleration values in X, y and Z directions. It mainly measures some actions of instantaneous acceleration or deceleration.  For example, measuring the speed and direction of the mobile phone, when the user holds the mobile phone, it will swing up and down, so that the acceleration can be detected to change back and forth in a certain direction, and the steps can be calculated by detecting the number of times of the change back and forth. In the game, the acceleration sensor can trigger special instructions. This sensor is also used in some daily applications, such as shaking and cutting songs, turning and muting. The power consumption of acceleration sensor is small but its accuracy is low. Generally used in mobile phones, it can be used to measure steps and judge the direction of mobile phones. 2.2 Gravity sensorThe gravity sensor is realized by piezoelectric effect. There are a heavy object and piezoelectricity piece integrated into the gravity sensor. The horizontal direction is calculated by the voltage generated in the two orthogonal directions. The gravity sensor used in the mobile phone can be used to switch between horizontal and vertical screen directions.In some games, gravity sensors can also be used to achieve more interactive control, such as balance ball, car games and so on. 2.3 Light sensorThe light sensor is similar to the eye of a mobile phone. The human eye can adjust the light entering the eye in a different light environment. And the light sensor can let the mobile phone sense the intensity of the ambient light, which is used to adjust the brightness of the mobile screen. Because the screen is usually the most power-consuming part of the mobile phone, the use of light sensors to help adjust the brightness of the screen can further extend the battery life. The light sensor can also be used with other sensors to detect whether the phone is placed in the pocket to prevent accidental contact. 2.4 Proximity sensorIt is composed of an infrared LED lamp and an infrared radiation light detector. The distance sensor is located near the handset of the mobile phone. When the mobile phone is close to the ear, the system uses the distance sensor to know that the user is on the phone and then turns off the display to prevent the user from affecting the call due to misoperation. The working principle of the distance sensor is that the invisible infrared light emitted by the infrared LED is reflected by nearby objects and detected by the infrared radiation light detector. The distance sensor is usually used with the light sensor. 2.5 Magnetism SensorThe magnetic field sensor uses magnetoresistance to measure the plane magnetic field, so as to detect the intensity and direction of the magnetic field. Magnetic field sensor is usually used in the common compass or map navigation to help mobile phone users achieve accurate positioning. Through the magnetic field sensor, you can obtain the magnetic field intensity of the mobile phone in X, y and Z directions. When you rotate the mobile phone until the value in only one direction is not zero, your mobile phone points to the right south. Many compass applications on mobile phones use the data of this sensor. At the same time, the specific orientation of mobile phone in three-dimensional space can be calculated according to the different magnetic field intensity in three directions. 2.6 GyroscopeGyroscope can measure the angular velocity along one or several axes, which is an ideal technology to supplement the function of MEMS accelerometer. In fact, if the accelerometer and gyroscope are combined, the system designer can track and capture the complete action of 3D space, and provide a more real user experience, accurate navigation system and other functions for end users. "Shake and shake" function in mobile phone (for example, shaking mobile phone can draw lots), body sensing technology, as well as VR angle adjustment and detection are all applied to gyroscopes. The gyroscope sensor is a necessary component for some induction games. With this sensor, the interaction of mobile games has a revolutionary change. Users can feedback the game with multi-directional operation of their bodies, not just simple buttons. Usually, the standard mobile phone is equipped with three-axis gyroscope, which can track the displacement changes in six directions. The three-axis gyroscope can get the angular acceleration of the current mobile phone in X, y and Z directions, which is used to detect the rotation direction of the mobile phone. Some functions of turning the mobile phone and answering the phone are realized by the change of angular acceleration. 2.7 GPS position sensorThere are 24 GPS satellites running in a specific orbit above the earth. They will continuously broadcast their position coordinates and time stamps(the total number of seconds since January 1, 1970, 00:00:00 GMT) to all parts of the world. The GPS module in the mobile phone starts from the instantaneous position of the satellite, and calculates the distance between the mobile phone and the satellite by the time difference between the time stamp of the satellite transmitting coordinate and the time of receiving. It can be used for positioning, speed measurement, distance measurement and navigation and so on.  GPS module is mainly used to receive the satellite coordinate information through the antenna to help users locate. With the popularization of 4G network, GPS is used in more scenarios, such as remote location monitoring with intelligent hardware, or location search after device loss. 2.8 Hall SensorThe function principle of Hall sensor is hall magnetoelectric effect. When the current passes through a conductor located in the magnetic field, the magnetic field will produce a force perpendicular to the direction of electron motion on the electrons in the conductor, thus generating potential difference at both ends of the conductor. The main function of the hall sensor installed on the mobile phone is to use the smart leather case (magnetic leather case). After the leather case is buckled, the screen will display a small window interface in the small window left on the leather case, which is used to answer calls or read short messages. 2.9 Air pressure sensorWhen the air pressure changes, the value of resistance or capacitance will change, so as to measure the air pressure data. GPS can also be used to measure altitude, but there will be an error of about 10 meters. If the air pressure sensor is installed, the error can be corrected to about 1 meter, which is helpful to improve the accuracy of GPS (Global Positioning System). In addition, when some outdoor applications need to measure air pressure, the mobile phone with air pressure sensor can also be used. In IOS health applications, you can calculate how many floors you have climbed. 2.10 Heart rate sensorIrradiate fingers with high brightness LED light, because the brightness (the depth of red light) will change periodically when the heart sends blood to capillaries. Then capture these regular changes through the camera, and transfer the data to the mobile phone for calculation, and then judge the heart contraction frequency to get the number of heartbeats per minute. The user's heart rate data is obtained by detecting the number of pulsations per minute of the blood vessels on the user's fingers. Heart rate sensors are common in wearable devices. 2.11 Blood oxygen sensorLike heart rate sensors, hemoglobin and oxyhemoglobin in blood have different absorption ratios for the red light. Infrared light and red light LED are used to irradiate fingers at the same time, and the absorption spectrum of reflected light is measured to measure blood oxygen content. Blood oxygen sensors can be used in sports or health applications. 2.12 UV sensorThe photoelectric emission effect of some semiconductors, metals, or metal compounds will release a large number of electrons under ultraviolet irradiation. The ultraviolet intensity can be calculated by detecting this discharge effect. UV sensor is also used in the field of sports and health and in detecting radiation levels in the environment.At present, there are few mobile phones using this kind of sensor, and the stability of the measurement needs to be further observed. 2.13 Temperature sensorMany smartphones are equipped with temperature sensors, and some have more than one. The difference is that their purpose is to monitor the temperature inside the phone and the battery. If it is found that the temperature of a certain part is too high, the mobile phone will be turned off to prevent damage. In terms of extended functions, the temperature sensor can also detect the temperature change in the outside air, even the user's current temperature. 2.14 Fingerprint sensorAt present, the mainstream technology is capacitive fingerprint sensor, but ultrasonic fingerprint sensor is also gradually popular. When the capacitive fingerprint sensor works, the finger is one pole of the capacitance, and the other is a silicon chip array. Through the microcurrent generated between the human body's micro-electric field and the capacitance sensor, the distance between the fingerprint's peak and valley and the sensor forms the capacitance height difference to describe the fingerprint pattern. The principle of ultrasonic fingerprint sensor is similar, but it will not be interfered by sweat and oil, and the recognition speed is faster. It can be used in mobile phones to unlock, encrypt, pay and so on. It can automatically collect user fingerprint to protect privacy, which is usually used as a security measure.Ⅲ Integrated application of sensors in the phoneNowadays, the technology level of smartphones is rapidly updated, which is largely due to the innovation and breakthrough of sensor technology in mobile phones. With the integrated application and software support of basic sensors, mobile phone researchers have developed many cool mobile phone functions. ① Super safe 3D ultrasonic fingerprint recognitionThe mobile phone integrates Xiaolong 820 chipset and Xiaolong sense ID. Among them, Xiaolong sense ID adopts the latest ultrasonic technology developed by Qualcomm to realize 3D fingerprint recognition. Fingerprint press recognition technology has become the standard equipment of some smartphones. Different from the previous technology, Qualcomm snapdragon sense ID can work even when there is a little dirt or moisture in the user's fingers, and can even penetrate glass, aluminum, stainless steel, sapphire, plastic and other equipment for identification. This means that mobile phone manufacturers can integrate sensors and devices without having to make fingerprint identification units into a single button. Therefore, ultrasonic fingerprint recognition technology can be put into the screen window of the flat panel. In addition, in terms of security, it has been greatly improved. Ultrasound has been used in the field of professional biometrics for a long time. It can penetrate the epidermis and detect the three-dimensional details of fingerprint, making it difficult for hackers to copy fingerprint and invade users' mobile phones. ② Iris recognition of mobile phoneThe iris of human eye is more complex than fingerprint, so it is safer to use iris recognition to unlock mobile phone than fingerprint recognition. Users only need to capture the eyeball through a special app, log the iris pattern of the eye onto the terminal, and then they can use it safely. Iris mobile phone will become the wallet for everyone to pay, the gold card of the bank, the key to open the door, the certificate for customs clearance and the evidence for medical insurance, opening a new generation of Internet identity authentication. The mobile phone's built-in micro iris recognition product consists of imaging module, lighting module and software algorithm. It can scan the user's iris features through the built-in camera, and the user only needs to stare at the screen for a short time. The effective recognition distance is 20 ~ 30cm, and the recognition speed is 1s. Based on the capsaic security chip and metacentric dual operating system independently developed by Spreadtrum, the iris recognition scheme is optimized from the aspects of system imaging, feature description and matching, security and anti-counterfeiting, user interaction, etc., to achieve accurate recognition. ③ RWB technology creates an intelligent and beautiful imageThe mobile phone with RWB technology is equipped with f1.8 aperture and 6p lens. Compared with the photos taken by the previous RGB technology models, the noise reduction ability is increased by 80%, the sensitivity is increased by 40%, and the area is reduced by 23%. The smaller rear camera mirror volume is used to obtain more light, and the details under weak light will be better. The image sensor of Bayer array usually uses RGB (red, green and blue) technology. On average, the whole sensor will block two-thirds of the incident light, resulting in a great waste. RWB (red, white and blue) has the greatest improvement compared with the traditional Bayer array sensor, which is the high sensitivity shooting performance. As the green pixel is replaced by the white pixel, the effective light intensity received by the sensor almost doubles, and the RWB's high sensitivity index has also been significantly improved. ④ Leica dual cameraLeica Summit Series dual lens with better brightness and clarity makes it easier to take photos and videos. The rear 12 megapixel black-and-white and color dual cameras have more than just two 12 megapixel lenses. In the process of photographing, the dual cameras work at the same time, and the black and white lens capture the details to make the image clearer; the color lens capture the color to make the color fuller, and the image synthesis algorithm makes the details and the colors more integrated, so the picture is lifelike and amazing. By using the hybrid focusing technology of laser focusing, depth focusing and contrast focusing, we can take the wonderful pictures with clear picture and clear layers in an instant. Mobile phone for comprehensive health exercise monitoringThis mobile phone attaches great importance to the health of users. It is equipped with ten major professional sensors, with low power consumption, which can realize users' 24-hour use of professional sports applications. In addition, more sensors allow the phone to restore the user's real movement, accurate to three steps of movement, while also measuring heart rate, blood oxygen and ultraviolet. With the support of the application algorithm, the user's stride and stride frequency can also be accurately identified. ⑤ 3D visual sensory experience of eye-tracking technologyThe concept of "full display mobile phone" has two cameras in front of it. One is used for taking photos like ordinary mobile phones, while the other is used for eye tracking and capturing the position of human eyes. According to your eye position and pupil distance, a reasonable visual angle image matching the position of human eyes is customized and generated in real-time. Whether it's left and right or front and back movement, you can get a comfortable and clear 3D visual sensory experience all the way. "One screen, two cores and three cameras" is standard for full display mobile phones. ‘One screen’ is the naked eye 3D cylindrical grating LCD screen, users can experience the shock of 3D and VR vision without wearing 3D glasses, and they can realize the free switching of 2D / 3D. ‘Two cores’ is that in addition to the CPU, there is an independent VR visual motion chip to improve the 3D / VR rendering speed. ‘Three cameras’ is that in addition to conventional cameras, eye-tracking cameras are added. ⑥ Video integrated mobile phone’s free conversion of 2D / VR The mobile phone realizes the integration of VR camera and mobile phone. It is equipped with four cameras, two at the front and two at the back, which can meet the demand of 360-degree panoramic shooting, realize 3D stereo effect, and also can freely switch between VR lens and 2D plane lens at the same time. The pixels of CMOS image sensor in VR camera module reach 26 million, and Sony photosensitive device is used. The thickest part of the camera module of ultra-thin VR panoramic lens is only 23.8mm, which is the thinnest mobile VR camera module in the world. VR mobile camera uses a single binocular zigzag two in one super wide angle camera module. This VR camera module contains two imaging systems with the same structure. Each imaging system is composed of a 200 degree super wide angle lens and an imaging sensor. The lens optical path adopts 90 degree zigzag double optical path design. The optical axis of the two cameras is the same, greatly reducing the lens volume to achieve ultra-thin and ultra light integrated structure. VR camera module also integrates the front and rear VR camera scenes into a sphere through image recognition, splicing and other algorithms, so that the pixel size, color, brightness and other parameters of the two hemispheres are the same, which is the first in terms of technology.Ⅳ SummaryThe development of sensors in the future is sure that they will know more about the surrounding environment, that is to say, the types of sensors will be far more than these. The bolder assumption is that in the future, sensors will not only perceive but also have certain processing capacity. What sensors transmit is not only data, but also some intelligent operation and judgment. In terms of sensor technology, it is the common understanding of the whole industry that sensor integration is getting higher and higher. The higher integration degree leaves more possibilities for the expansion of sensors, and greatly saves the equipment space, which is more conducive to the development of mobile devices towards portability. I believe that in the foreseeable future, the perception of our mobile phone to users will be more accurate, and its application in the future will be far richer than we think now. Ⅴ FAQ1. What sensors does a phone have?• Accelerometer.• Ambient Light Sensor.• Ambient Temperature Sensor.• Air Humidity Sensor.• Barometer Sensor.• Finger Print Sensor.• Gyroscope Sensor.• Harmful Radiation Sensor and so on. 2. How many sensors are there in mobile?Today's mobile devices are packed with nearly 14 sensors that produce raw data on motion, location and the environment around us. This is made possible by the use of micro-electromechanical systems (MEMS). 3. How many types the capacitive touch sensors are classified?There are two types of capacitive touch sensors: surface capacitive sensing and projected capacitive sensing. In surface capacitive sensing, an insulator is applied with a conductive coating on one side of its surface. On top of this conductive coating, a thin layer of the insulator is applied. 4. What is the proximity sensor on phone?In Android, the proximity sensor is primarily used to detect when the user's face is close to the screen. ... This is how the phone screen seems to know to switch off when you hold it up to your ear during phone calls, preventing any errant button presses. 5. Do phones have a motion sensor?Most Android-powered devices have an accelerometer, and many now include a gyroscope. The availability of software-based sensors is more variable because they often rely on one or more hardware sensors to derive their data. 6. Which sensor is used in the touchscreen?Optical touchscreens use infrared emitters combined with infrared image sensors to continuously scan the touchscreen. When an object comes into contact with the touchscreen, it blocks some of the infrared light being received by the sensors. 7. What is a simple touch sensor?The Touch Sensor is sensitive to touch, pressure as well as force. The Touch Sensor works similar to that of a simple switch. When there is contact or a touch on the surface of the Touch Sensor. It acts like a closed switch and allows the current to flow through it. 8. How do I find the sensor code on my phone?To get the ball rolling, simply open your Samsung phone app. From there, enter *#0*# using the dial pad, and the phone will immediately go into its secret diagnostic mode. Note that the process is automatic, so there's no need to tap on the green call button to enter the command. 9. How accurate are phone gyroscopes?They used an algorithm designed for repetitive, well-defined, and bounded pedaling leg movement. Their results show that the achieved accuracy of gyroscope angular tracking in pedaling is in the range of 2.2°–6.4°. Many works have been published on golf swing motion tracking. 10. What is a depth sensor in mobile?The DepthVision Camera is a Time of Flight (ToF) camera on newer Galaxy phones including Galaxy S20+ and S20 Ultra that can judge depth and distance to take your photography to new levels. ... With Quick Measure, the camera acts as a 3D camera, judging width, height, area, volume, and more when you put an object in the frame. 

CatalogⅠ The Role of the FuseⅡ Working Principle of the FuseⅢ Classification of the FuseⅣ The Terminologies of the FuseⅤ Safety Standards and Signs for Fuse TubesⅥ Factors Affecting Fuse Life and Evaluation of Fuse Life6.1 Factors Affecting the Life of the Fuse6.2 Effect of the Use of the Fuse After Aging6.3 Test Evaluation of Fuse LifeⅦ Fuse Suitable CircuitⅧ Precautions for Using the Fuse TubeⅨ Selection of Fuse TubeⅩ FAQⅠ The Role of the Fuse• Under normal circumstances, the fuse acts as a connection circuit in the circuit.• In the case of abnormal (overload), the fuse acts as a safety protection element in the circuit, and safely cuts off and protects the circuit by blowing itself. Figure 1.Ⅱ Working Principle of the FuseWhen the fuse is energized, the heat converted by the electrical energy causes the temperature of the meltable item to rise. When the normal working current or the allowable overload current passes, the generated heat is radiated to the surrounding environment through the meltable body and the outer casing, and the heat generated by convection, conduction, etc. is gradually balanced with the generated heat. If the generated heat is greater than the amount of heat dissipated, the excess heat gradually accumulates on the meltable item, causing the temperature of it to rise; when the temperature reaches and exceeds the melting point of the meltable item, it will be melted, blown and the current will be cut off and plays a role as a safety protection circuit. Ⅲ Classification of the Fuse• According to the external size, it is divided into φ2, φ3, φ4, φ5, φ6 and others. • According to the blowing characteristics, it is divided into fast-blown type, medium time-delay blown type, and time-delay type. (it can also be divided into express, strong delay). • According to the breaking capacity, it is divided into low breaking type and high breaking type (it can also be divided into enhanced breaking type). • According to safety standards (or areas of use): UL/CSA (North America) specification, IEC (China, Europe, etc.) specification, MIT/KTL (Japan/Korea) specification, etc. • Other classifications. Ⅳ The Terminologies of the Fuse• Rated current: The nominal operating current of the fuse tube (the maximum current that the fuse maintains normal operation for a long time under normal conditions). • Rated voltage: The nominal working voltage of the fuse (the maximum voltage that can safely withstand when the fuse is disconnected). When a fuse is selected, the rated voltage of the selected fuse should be greater than the input voltage of the protected circuit. • Breaking capacity: When a large overload current (such as a strong short circuit) occurs in the circuit, the fuse can safely cut off (break) the maximum current of the circuit. It is the most important safety indicator for fuses. Safe breaking means that something endangers the surrounding elements, components and even personal safety such as splashing, burning, the explosion will not happen in the breaking circuit.  • Overload capability (load carrying capacity): The fuse can maintain the maximum overload current for working within the specified time. When the current flowing through the fuse exceeds the rated current, the temperature of the meltable item will gradually rise after a period of time and eventually be blown. The UL standard stipulates that the fuse remains in operation for more than 4 hours, and the maximum unblown current is 110% of the rated current (100% for the miniature fuse tube) The IEC standard stipulates that the fuse remains in operation for more than one hour, and the maximum unblown current is 150% of the rated current. • Fuse characteristics (I-T): The relationship between the load current applied to the fuse and the fuse blowing time. Blowing characteristic curve (I-T curve): A curve formed by the average blowing time coordinate point of the fuse under different load currents in a logarithmic coordinate system in which the load current is the X-axis and the blowing time is the Y coordinate. Each type of fuse has a corresponding curve that represents its blowing characteristics, which is a good indication of the fuse's overload performance and it is for reference when selecting the fuse. Blowing characteristics table: A table consisting of several specified representative load current values and corresponding blowing time ranges. All safety standards have clearly stated that this is the most important basis for the acceptance of fuses. For example, fast-blow type such as UL, CSA, MIT/KTLA, is specified as:In 100% 4 hours(minimum)In 135% 1 hour(maximum)In 200% 2 minutes(maximum) • Melting heat value (I2t): The nominal energy value that the cut-off current needed to melt and partially carburate the fuse, which is simply the minimum amount of heat required to blow the fuse. Total I2t=melted I2t+ arcing I2t The melting I2t (corresponding to the pre-arcing I2t in the IEC standard) refers to the energy required from the melting of the fuse to the moment of arcing; the arcing I2t refers to the energy required for the arcing from the moment it starts to the moment it eventually extinguishes. For low-voltage fuses, the arcing time is very short and often negligible. That is to say, the arcing I2t can be calculated as zero. Both UL and IEC do not require I2t, but I2t has some help with fuse selection. The I2t measurement of the fuse is calculated as I2t when the fuse's blowing time is less than 10ms (usually 8ms). • Voltage drop: The voltage difference across the fuse after thermal equilibrium underrated current conditions. • Temperature rise: Under a certain current condition, the difference between the surface temperature of the fuse and the initial temperature of the energization (which can be understood as the ambient temperature) after the heat balance is reached, that is, the temperature rise = the surface temperature of the fuse - the ambient temperature. Figure 2.Ⅴ Safety Standards and Signs for Fuse Tubes• UL, CSA standards: North American regional safety standards such as the United States, Canada; small current fuse tube standards are UL248-1/14, CSA248-1/14.Safety sign:--- UL/CSA LIST (Listing Sign), the product safety sign passed the test in accordance with UL/CSA248-1/14.--- UL/CSA RECOGNIZED (Approved Sign), the product safety mark passed the test partly in accordance with UL/CSA248-1/14. • JIS Standard: Japanese Electrical Safety Standard. The standard for small current fuse tubes is JIS C6575.Safety sign:--- T--- PSEBoth signs were valid before the end of 2006, after which only the “PSE” mark was valid. • KTL Standard: Korean Electrical Safety Standard.Safety sign:--- K • IEC standards: International Electrotechnical Commission standards and safety standards used in Europe and China. The standard for small current fuse tubes is IEC60 127, GB 9364 (China).Safety sign:CCC --- ChinaSEMKO --- SwedenVDE --- GermanyBSI --- UKIMQ --- Italy Ⅵ Factors Affecting Fuse Life and Evaluation of Fuse Life6.1 Factors Affecting the Life of the Fuse• Working environment temperature:Excessive ambient temperature is detrimental to the life of the fuse. Time-delay (slow-blow) fuses, such as tin ball type, begin to spread to the wire when the temperature is approximately 160℃ (150-170℃); the meltable item (wire) of the fast-blow fuse begins to violently oxidize at a temperature approximately equal to 200℃ (175 to 225℃). As the fuse is oxidized from the outside to the inside, multiple times of diffusion, thermal stress fatigue, etc., the life of the fuse will be gradually shortened. Therefore, it is recommended that the time-delay fuse should not work above 150℃ for a long time, and the fast-blow fuse should not work above 175~225℃ for a long time. • Pulse current:Constant pulse shock will cause thermal cycling, which will cause the diffusion, oxidation, thermal stress, etc. of the fuse to be generated and even accelerated. The fuse will age as the pulse energy and frequency increase. The impact resistance life of the fuse depends on the I2t of the pulse as a percentage of the fuse's own I2t; normally, it should be less than 20%, so that the fuse can withstand more than 100,000 times of impact. • Other:Such as the tube clamp in contact with the fuse, and the length and cross-sectional area of the connecting wire. The contact resistance between the fuse and the pipe clamp is large, which is detrimental to the service life. The UL standard specifies that the contact resistance between the fuse to the tube clamp is less than 3mΩ during the test. When the contact resistance is large, the tube clamp does not dissipate heat but generates heat and transmits it to the fuse. 6.2 Effect of the Use of the Fuse After AgingAfter the fuse has aged, the situation that the current should be cut off and the fuse is not blown will not happen. When the fuse ages, it is equivalent to a drop in the rated value (current) rather than a rise, so there is no safety problem in the circuit, but the circuit is cut off under a small overload current or pulse. 6.3 Test Evaluation of Fuse LifeThe "endurance test method" is specified in the IEC standard, and there is no similar regulation in the UL standard. The durability test in the IEC standard is the life test by using the DC power supply test at normal temperature:• The voltage drop is measured until the temperature is stable under the rated current;• 1.2 times of rated current for 1h, cut off current for 15min and circulate for 100 times;• Power on 1.5In for 1h and measure voltage drop;• Measure the voltage drop with method a. Requirements: The voltage drop change before and after the test should not exceed 10%, and the sign is still clear and identifiable, and the end cap solder joint does not show any deterioration. Figure 3.Ⅶ Fuse Suitable Circuit• Very fast and fast-blow type fuse tubes: Suitable for circuits with relatively constant current, or circuits with low inrush current, and there are shock-resistant fragile components in the circuit. • Medium time-delay and time-delay blown fuse tubes: Suitable for circuits with normal inrush current, and there are no shock-resistant fragile components in the circuit. Lightning-resistant fuse tube for special circuits that need to withstand lightning strikes, such as telephones. • Breaking current fuse tube: Suitable for circuits where large short-circuit current may occur. • Oxygen resin package and plastic case type fuse tube: suitable for installation of dense components or circuits where contact short circuits may occur. • 350V, 300V fuse tube: suitable for electronic rectifiers and other products. Ⅷ Precautions for Using the Fuse Tube1. The rated voltage of the selected fuse should be greater than the input voltage of the protected circuit. 2. The rated current of the UL specification fuse is determined under laboratory conditions and should be used less than 75% of the nominal value in actual use. For example, the circuit operating current is 0.75A, we can select the fuse tube with a minimum rated current of 1A. 3. The rated current of the IEC specification fuse tube can be used at 90% or 100% of the nominal value in actual use. For example, the circuit operating current is 0.9A, and the fuse tube with a minimum rated current of 0.9A or 1A can be selected. 4. Under different operating environment temperatures, the working life of the fuse is different. The higher the temperature, the shorter the working life of the fuse. In actual selection, the rated current of the fuse should be increased according to the coefficient. 5. The breaking capacity of the fuse tube is proportional to its volume and inversely proportional to the rated voltage, that is, the larger the volume or the smaller the rated voltage, the larger the breaking capacity of the fuse tube; the smaller the volume or the larger the rated voltage, the smaller the breaking capacity of the fuse tube. Therefore, if a small-size fuse tube is used, it is necessary to determine that the short-circuit current that may occur in the protected circuit is not too large; if a large short-circuit current may occur in the protected circuit, a larger-size fuse tube with a larger breaking current must be selected. 6. The surge I2t of the protection circuit should be less than 20% of the rated I2t of the fuse tube. The fuse tube can withstand more than 100,000 surges in the protected circuit. Ⅸ Selection of Fuse Tube1. Determine the safety sign: According to the market requirements for the product to be sold, select the safety certification sign and safety standard (UL standard or IEC standard fuse tube) of the fuse tube. 2. Determine the dimensions of the fuse tube: Select the dimensions of the fuse tube according to the installation space and the defined safety certification sign and safety standards. 3. Determine the model number: Select the type of fuse tube based on the current characteristics of the circuit being protected. For example, if the current characteristic of the protected circuit is a constant current, the fast-blow type should be selected. 4. Determine the rated voltage: Determine the rated voltage of the fuse tube according to the input voltage of the protected circuit and the requirements for use. For example, if the input voltage of the protected circuit is 220V, the fuse tube with rated voltage above 220V should be selected, 250V, 300V, 350V, etc. can also be selected; but considering the cost factor, it is not necessary to use the rated voltage which is too high. 5. Determine the minimum rated current: According to the stable operating current of the protected circuit and the relevant use loss factor, the rated current of the fuse tube is initially determined. For example, the stabilized working current of the protected circuit is 1A, the UL standard time-delay fuse tube should be selected, and the working environment temperature is about 80℃. The minimum rated current of the fuse tube is selected as 1A × 1.25 ÷ 0.5 = 2.5A. 6. Determine the minimum I2t of the fuse tube: Determine the I2t of the fuse tube based on the surge I2t of the protected circuit. For example, the surge I2t of the protected circuit is 1 (A2S). To ensure that the fuse tube can withstand more than 100,000 times of impact, the I2t of the fuse tube should be greater than 1÷0.2=5 (A2S). 7. Determine the rated current of the fuse tube: According to the minimum rated current and the minimum I2t value, check the corresponding model specifications, and take the primary rated current specification that is greater than the minimum rated current value and whose I2t value is also greater than the minimum I2t value as the rated current of the selected fuse tube. For example, based on the above minimum,(1) If the I2t of the rated current of 2.5A is 4.3A2S and the I2t of 3A is 5.4A2S, take 3A as the rated current of the selected fuse tube;(2) If the I2t of rated current of 2A is 5.3A2S and the I2t of 2.5A is 7.6A2S, take 2.5A as the rated current of the selected fuse tube. Ⅹ FAQ1. What is Fuse?A Fuse or an Electric Fuse is an Electrical / Electronic device that protects the circuit from different electrical faults like over-current and overload. Fuses can be considered sacrificial elements in the circuit as they act as a weak link in the entire circuit. 2. What is the working principle of fuse?An electric fuse is based on the principle of the heating effect of electric current. It is made up of thin metallic wire of non-combustible material. A fuse is always connected between the ends of the terminal in a series connection with the circuit. 3. What is the application of fuse?Used to protect transformers, motors and power systems from over-current conditions. In feeders, power transformers, and solar circuits. Electrical appliances and house distribution boards use fuse for domestic purposes. 4. What is the type of fuse?Fuses can be divided into two major categories, AC fuses, and DC fuses. The below block diagram illustrates the different types of fuse under each category.  5. Are fuses AC or DC?Generally, fuses have a DC voltage rating that is half of the maximum AC voltage rating. 6. Why fuse is not used in the neutral wire?Because the fuse can disconnect the circuit only when the excess current flows completely through the neutral. ... Since, neutral is not a live conductor coming from the source, disconnecting a neutral line can only open the current path through neutral. But, the live phase still carries the charge. 7. How do I choose a fuse size?In order to select the right amperage of the fuse, you first need to know the full-load steady-state current of the circuit at an ambient temperature of 25º C (68º F). Once the current value is determined, then a fuse rating should be selected to be 135% of this value (taken to the next standard value). 8. How do you use fuses in a circuit?Fuses should always be connected to the hot wire and should be placed before any other component in the circuit. In most projects, the fuse should be the first thing the hot wire connects to after it enters your project enclosure. 9. How long do fuses last?Fuses never need to be replaced unless they are tripped/activated by a failing component or any other even with the circuits of the car. They are encapsulated in plastic and are in a vacuum inside the piece. As long as the current limit isn't reached, that wire will not burn out. 10. Do fuses reduce voltage?The voltage rating of a fuse must be at least equal to or greater than the circuit voltage. It can be higher but never lower. ... If a fuse is used with a voltage rating lower than the circuit voltage, arc suppression will be impaired and, under some overcurrent conditions, the fuse may not clear the overcurrent safely. 

Ⅰ IntroductionWith the improvement of computer technology, the demand for non-volatile memory is increasing, their read and write speed requirements are getting faster and faster, and the power consumption  are becoming smaller and smaller as required by users. But the traditional non-volatile memory such as EEPROM , FLASH, etc. have been difficult to meet these needs.Traditional mainstream semiconductor memories can be divided into two categories: volatile and nonvolatile. Volatile memory includes static random access memory (SRAM) and dynamic random access memory (DRAM). Both SRAM and DRAM lose their saved data when power off. Although RAM is easy to use and performs well, a big disadvantage of it is data loss.Non-volatile memory does not lose stored data in the case of a power failure, because all mainstream non-volatile memories are derived from read-only memory (ROM) technology. ROM, what is called a read-only memory is definitely not easy to write, in fact, it cannot be written at all. All memories developed by ROM technology are difficult to write data, including EPROM, EEPROM and Flash. And these memories not only have a slow writing speed, but also can only be erased and written in a limited number of times.Based on improving semiconductor technologies, ferroelectric memory, a new type of memories, has some unique characteristics. Ferroelectric memory is compatible with all the functions of RAM, and it is a non-volatile memory like a ROM. In other words, ferroelectric memory bridges the gap between these two types of storage, a type of non-volatile RAM. Compared with traditional non-volatile memory, it has attracted much attention due to its advantages such as low power consumption, fast read and write speed, and strong anti-irradiation capability. CatalogⅠ IntroductionⅡ TerminologyⅢ Working PrincipleⅣ FRAM Material FeaturesⅤ Circuit StructureⅥ Reading and Writing ProcessⅦ FRAM StructureⅧ Comparison of FRAM with Other Storage TechnologiesⅨ FRAM UsageⅩ SummaryⅪ One Question Related to FRAM and Going Further11.1 Question11.2 AnswerⅡ TerminologyFerroelectric Memory (FeRAM)Ferroelectric memory (FRAM), also known as F-RAM or FeRAM, is a type of random access memory with fast read and write speed, and the ability to retain data after power is turned off (such as read-only memory and flash memory) is combined, which is the most commonly used type of personal computer memory. Since it is not as dense as dynamic random access memory (DRAM) and static random access memory (SRAM), that is, it cannot store as much data as they do in the same space. In other words, it cannot replace DRAM and SRAM technologies. However, because it can store data quickly with very low power conditions, it is widely used in consumer’s small devices, such as personal digital assistants (PDA), mobile phones, power meters, smart cards, and security systems. FRAM’s read and write speed is faster than flash memory. In some applications, it may also replace electrically erasable read-only memory (EEPROM) and static random access memory (SRAM), and will become a key component of future wireless products. Ⅲ Working PrincipleFeRAM or ferroelectric RAM seems to indicate that an iron element exists within the memory this is not actually the case. A ferroelectric is a material containing a crystal that can spontaneously polarize. It has two states that can be reversed by an external electric field. When an electric field is applied to the ferroelectric crystal, the central atom moves in the crystal following the electric field direction. When an atom moving, it passes through an energy barrier, causing charge breakdown. Internal circuits react to the charge breakdown and set the memory. After the electric field is removed, the central atom remains polarization state, which makes the materials non-volatile, so the state of the memory is preserved. Because there is no atomic collision in the entire physical process, the ferroelectric memory has the characteristics of high read and write speed, ultra-low power consumption, and unlimited writes, making it very suitable to act as temporary storage memory in important systems to transfer various data between subsystems, for each subsystem to read and write frequently.Therefore, with an external electric field, the polarization characteristics of ferroelectric materials will change. When this electric field is removed, the data can still be saved. Without an external electric field, there are two stable states of polarization characteristics. Figure 1 is a hysteresis loop of a ferroelectric material capacitor, showing the different polarities of the ferroelectric capacitor under different applied electric fields. Among them, the two most important parameters are the degree of residual polarization Pr, and the coercive field Ec. In the absence of electric field effect, +/- Pr represents two states of “0” and “1”. To obtain these two states, the applied electric field must be greater than +/- Ec, at this time, the required threshold voltage is also determined.Figure 1. Ferroelectric Hysteresis LoopThe industry explores the use of ferroelectric materials for DRAM: using them as dielectric materials in DRAM capacitors. That is, ferroelectrics are used to replace high-K dielectric materials in standard logic devices, and finally non-volatile transistors are formed, which are FeFETs. The two stable polarization states of the ferroelectric gate oxide change the threshold voltage of the transistor, even when the supply voltage is removed. Therefore, the binary state is encoded in the threshold voltage of the transistor. The writing operation of the memory cell can be completed by applying a pulse on the gate of the transistor, which will change the polarization state of the ferroelectric material and affect the threshold voltage. For example, applying a positive pulse will reduce the threshold voltage, making the transistor in the “on” state. Reading is done by measuring the drain current. This memory mode is similar to the operating mode of a NAND flash: electrons are injected and drawn out of the floating gate, which adjusting the threshold voltage of the transistor.In contrast, the leakage current factor of ferroelectric capacitors is not as important as traditional non-volatile memories such as EEPROM and FLASH, because the information storage of FeRAM is realized by polarization, not free electrons. Ⅳ FRAM Material FeaturesIdeal ferroelectric materials need to meet the following characteristics:Small dielectric constantReasonable self-polarization degree (~ 5μC/ cm2)High Curie temperature (outside the storage and operating temperature range of the device)The thickness of ferroelectric materials should be thin (submicron) to make the coercive field EC smaller. Ferroelectric materials should stand a certain breakdown filed strength.Internal switching speed should be fast (nanosecond level)The ability to keep the data and the long-lasting ability will be good.If used by the military, it is also required to be able to resist radiation exposure. Good chemical stabilityGood processing uniformityEasy to integrate into CMOS processNo bad effect on the surrounding circuitsSmall pollution After years of research and development, there are currently two main types of mainstream ferroelectric materials: PZT and SBT.PZT is lead zirconate titanate PbZrxTil-xO3; SBT is strontium bismuth tantalate Sr1-yBi2 + xTa2O9. The structure of these two materials is shown in Figure 2. Figure 2. Schematic Diagram of PZT and SBT Material StructurePZT is the most studied and widely used. Its advantage is that it can be made at lower temperatures by sputtering and MOCVD. It has the advantages of large residual polarization, cheap raw materials, and low crystallization temperature.; its disadvantages are fatigue degradation problems, and lead pollution to the environment. Moreover, the film deposition process of these materials has proved to be very challenging. At the same time, the extremely high dielectric constant (about 300) of these materials is a big obstacle to their integration into transistors.In addition, scientists have discovered the presence of a ferroelectric phase in a less complex material, hafnium oxide (HfO2), which raise a new concept of storage concept. The researchers found that the ferroelectric phase) can be stabilized by doping silicon (Si) into HfO2. Compared with PZT, HfO2 has a lower dielectric constant and can deposit thin films in a conformal manner (ie, the atomic layer deposition (ALD) process). Most importantly, scientists are familiar with HfO2, because it is the HK gate oxide material in the logic device HKMG. By modifying this CMOS-compatible material, logic transistors can become non-volatile FeFET memory transistors.Functional verification of FeFETs has been implemented in a two-dimensional planar architecture. At the same time, the HfO2 conformal deposition process makes 3D stacking possible, for example, depositing ferroelectric materials on vertical “walls’ to stack transistors in a vertical direction.In terms of materials, 3D FeFETs can solve some of the challenges brought by 2D FeFET structures. One challenge is related to the polycrystalline nature of the HfO2. Scaling the thickness of the HfO2 film will significantly reduce the number of grains in this layer. Because not all the crystal grains have the same polarization direction, the reduction of crystal grains will affect the consistency of the transistor’s response to the external electric field, and eventually lead to large differences between the tubes. By 3D stacking, this drawback is overcome in physical filed. That is, HfO2 does not need to be compressed too thinly, thereby reducing tube-to-tube variation.These vertical FeFETs are expected to have more advantages than complex 3D NAND flash memory, including simple process, lower power consumption and faster speed. Compared to 3D NAND flash memory, vertical FeFET can be programmed at a lower voltage, which improves memory reliability and scalability.The biggest advantage of SBT is that it does not have the problem of fatigue degradation, and it does not contain lead, which meets EU environmental standards; however, its disadvantages are that the process temperature is higher, which makes the process integration difficult, and the degree of residual polarization is small. The comparison of the two materials is shown in Table 1.Table 1. Comparison between PZT and SBT  PZTSBTStructureABO3Layered structureDeposition technologySol-gel,MOCVDSol-gel,MOCVDProcess temperature450℃~700℃750℃~850℃Residual polarity3012Fatigue10101010Data hold85℃@10a- At present, from the perspective of environmental protection, PZT has been banned, but from the perspective of performance and process integration of ferroelectric memory and cost, SBT has no advantages compared to PZT. Therefore, the selection of ferroelectric materials is worth discussing. Ⅴ Circuit StructureThe circuit structure of the ferroelectric memory is mainly divided into the following three types: 2 transistors-2 capacitors (2T2C), 1 transistor-2 capacitors (1T2C), 1 transistor-1 capacitor (1T1C), as shown in Figure 3. The 2T2C structure has two opposite capacitors for each bit as a reference to each other, so the reliability is better, but occupies too much space, which is not suitable for high-density applications. The transistor / single capacitor structure can be used like a DRAM to provide a reference for each column of the memory array, compared with the existing 2T2C structure, they effectively reduce the required space of the memory cell by half. This design greatly improves the efficiency of ferroelectric memory and reduces the production cost of ferroelectric memory products. The 1T1C structure has a higher integration density (8F2), but its reliability is poor. And the 1T2C structure is a compromise between these two structures. Figure 3. Three FRAM StructuresAt present, in order to obtain a high-density memory, 1T1C structure is mostly used (as shown in Figure 4). In addition, a chain structure is also adopted, thus Chain FeRAM is made. This structure is similar to the NAND structure. Through this method, a higher storage density than 1T1C can be obtained, but this method will also greatly increase the access time. Chain FeRAM (CFeRAM) structure is shown in Figure 5. Figure 4. 1T1C Layout Figure 5. Chain FeRAM (CFeRAM) Circuit StructureⅥ Reading and Writing ProcessAccording to the polarity of the electronic memory cell, a small charge amount is “0” and a large charge amount is “1”. This charge is converted into a reading voltage, which is “0” when it is less than the reference voltage and when it is greater than the reference voltage represents “1”. The stored information is read out as shown in Figure 6. Figure 6. Reading and Writing Process of FRAMDuring the reading process, the word line voltage is increased to turn on the MOS transistor, and then the drive line voltage is increased as VCC, so that different charges of the storage capacitor are distributed to the bit line parasitic capacitance, so different voltages appear on the BL to identify the data. During a writing process, the word line is raised to turn on the MOS transistor, and a pulse is applied to the drive line, so that different data on the bit line are stored in two different steady states of the ferroelectric capacitor.By adding a positive voltage or a negative voltage, these two voltages can make the capacitor into two different polarities. In this way, the information is written into the memory. Ⅶ FRAM StructureAt present, the most common device structures of ferroelectric memories are planar and stack structures. The difference between the two is the location of the dry ferroelectric capacitor and the way in which the capacitor is connected to the MOS tube. In the planar structure, the capacitor is placed above the field oxide, and the electrode of the capacitor is connected to the active area of the MOS tube through metal aluminum. The process is relatively simple, but the unit spacing is large. In the stack structure, the capacitor is placed in the source region, the lower electrode of the capacitor is connected to the source terminal of the MOS tube through a plug based on CMP process, which has a high integration density. In addition, the stack structure can adopt the method of making ferroelectric capacitors on metal wires, thereby reducing the mutual influence during the formation process. The following schematic diagrams of the two structures are shown in Figure 7 and Figure 8. Figure 7. Planar Structure Figure 8. Stack StructureThe process of the planar structure is relatively simple. The isolation uses the LOCOS structure, and the planarization does not require the CMP. The stacked structure has a high degree of integration based on advanced technique, and STI is used for isolation, in addition, CMP is required for planarization, and copper wires can be used.In addition, there is a structure that uses a ferroelectric material as the gate. Such a device can eliminate the destructive problem of data readout, and theoretically it is more space-saving and can make more greater integration. However, there are still serious problems with this structure, that is, the data storage capacity is very poor, only one month or less, so it is far from practical. Figure 9 is a schematic diagram of such a structure. Figure 9. FeFET Structure DiagramAt present, the ferroelectric memory generally adopts a planar structure with the line width more than 0.5 μm, and generally uses a stack structure when the line width is less than 0.5 μm. Ⅷ Comparison of FRAM with Other Storage TechnologiesAt present, Ramtron’s FRAM mainly includes two categories: serial FRAM and parallel FRAM. Among them, serial FRAM is divided into I2C two-line FM24×× series and SPI three-line FM25xx series. Serial FRAM is compatible with the traditional 24xx and 25xx E2PROM pins and timing, which can be directly replaced.FRAM products have the advantages of RAM and ROM, and fast read and write speed, in addition, they can be used as non-volatile memory. Due to the shortcoming of ferroelectric crystals, the number of accesses is limited, beyond which FRAM is no longer non-volatile. The maximum access times given is 10 billion, but it not means FRAM will be scrapped when over this upper limit. In the terms of it, FRAM is not non-volatile, but it can still be used as an ordinary RAM.FRAM vs E2PROMFRAM can be used as a second option for E2PROM. Except the performance of E2PROM, the FRAM access speed is much faster. When using FRAM, it must be determined that once there are 10 billion accesses is down to FRAM in the system, there is no damage.FRAM vs SRAMIn terms of speed, price, and convenience, SRAM is better than FRAM; but from the perspective of the entire design, FRAM has certain advantages. Non-volatile FRAM can hold startup programs and configuration information. If the maximum access speed of all the memories in the application is 70ns, one piece of FRAM can be used to complete the system, making the system structure more simpler.FRAM vs DRAMDRAM is suitable for applications where density and price are more important than access speed. For example, DRAM is the best choice for graphics display memory. There are a large number of pixels to be stored, and the recovery time is not very important. If you don’t need to save the last content at the next boot, use volatile DRAM memory. The role and cost of DRAM are reasonable compared with FRAM. In short, it turns out that DRAM cannot be replaced by FRAM totally.FRAM vs FlashAt present, the most commonly used program memory is Flash, which is more convenient and cheaper to use. The program memory must be non-volatile, and easier to rewrite, but the use of FRAM is limited by access times.Ⅸ FRAM UsageData collection and recordingFeRAM allows designers to write data faster and more frequently, and at a lower price than EEPROM.Typical applications: meters (electric meters, gas meters, water meters, flow meters), RF/ID instruments, car black boxes, air bags, GPS, power grid monitoring systems, and so on. Parameter setting and storageFeRAM helps designers solve the problem of data loss due to sudden power failure by storing data in real time. Parameter storage in the FeRAM is used to track the changes of the system in the past time. Its purpose includes restoring the system state or confirming a system error when the power is on.Typical applications: photocopiers, printers, industrial controls, set-top boxes, network equipment  and large household appliances. Non-volatile bufferFeRAM can quickly store data before it is stored in other memory, so that the data in the buffer will not be lost when having power failure.Typical applications: industrial systems, ATM teller machines, tax control machines, commercial settlement systems (POS), fax machines, non-volatile cache memory in hard disk, etc. Ⅹ SummaryFerroelectric memory is an emerging non-volatile memory. It started early and realized industrialization. Because of its advantages such as low power consumption, fast read and write speed, and strong anti-irradiation capabilities, there is a market for small-scale storage areas with low power consumption and radiation resistance. Having the characteristic of anti-radiation, in the case of electromagnetic waves or radiation, the data is still safe, so it has important applications in space science, medicine and other specific fields. However, the ferroelectric memory also has the disadvantages that it is difficult to improve the integration, the process is more contaminated, and it is difficult to be compatible with the CMOS technique. So that it needs further research and solution. Ⅺ One Question Related to FRAM and Going Further11.1 QuestionWhat is FRAM used for?11.2 AnswerFerroelectric RAM is a random-access memory similar in construction to DRAM but using a ferroelectric layer instead of a dielectric layer to achieve non-volatility. It is one of a growing number of alternative non-volatile random-access memory technologies that offer the same functionality as flash memory. FRAM can be used in many fields, for example, with ultra-low power consumption, it is very suitable for intelligent water meters, gas meters and so on. Frequently Asked Questions about Ferroelectric RAM1. What is FRAM memory?Ferroelectric RAM (FeRAM, F-RAM or FRAM) is a random-access memory similar in construction to DRAM but using a ferroelectric layer instead of a dielectric layer to achieve non-volatility. 2. What is ferroelectric effect?Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. ... Thus, the prefix ferro, meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not contain iron. 3. How does FRAM work?FRAM is a nonvolatile storage memory that retains its data even after the power is turned off. However, similar to commonly used DRAM (Dynamic Random Access Memory) found in personal computers, workstations, and non-handheld game-consoles, FRAM requires a memory restore after each read. 4. What are the unique characteristics of FRAM?FRAM has the characteristics of both ROM (Read Only Memory) and RAM (Random Access Memory), and features faster write, great read/write cycle endurance, and low power consumption. 5. Which enables the read and write operation in Feram?Write Operation in Ferroelectric Random Access Memory (FRAM)Similar to read operation, a pre-charge operation follows a write access. The circuit applies 'write' data to the Ferroelectric capacitors. If necessary, the new data simply switches the state of the ferroelectric crystals.

IntroductionThermal relay is a protective device.  are protective devices. It is used in conjunction with a contactor to protect electric motors. The basic working principle of thermal relay is that, when a bimetallic strip is heated up by a heating coil carrying over current of the system, it bends and makes normally open contacts. Getting to know more about the thermal basics just check the following note. CatalogIntroductionⅠ The Working Principle and Structure of Thermal Relay  1.1 The Role and Classification of Thermal Relay  1.2 Protection Characteristics and Working Principle of Thermal RelayⅡ Selection and Setting Principle of Thermal Relay  2.1 Thermal Relay Selection Overview  2.2 Type Selection of Thermal Relay  2.3 Selection of Rated Current of Thermal Relay  2.4 Selection of Thermal Element Setting Current  2.5 Reliable and Reasonable Protection Characteristics of The Thermal Relay  2.6 Other ConsiderationsⅢ Other Matters Needing Attention  3.1 Installation Direction  3.2 Selection of Connecting Wires  3.3 Use Environment  3.4 Adjustment of Thermal RelayⅣ Frequently Asked Questions about Thermal RelayⅠ The Working Principle and Structure of Thermal Relay1.1 The Role and Classification of Thermal RelayIn the electric drag control system, when the three-phase AC motor runs under abnormal conditions such as long-term under-load and under-voltage operation, long-term overload operation, and long-term single-phase operation, it will cause the motor winding to overheat and even burn out. In order to give full play to the overload capacity of the motor, to ensure the normal start and operation of the motor, and once the motor is overloaded for a long time, it can automatically cut off the circuit, so that there are electrical appliances that can change the operating time with the degree of overload and that is thermal relay.  Obviously, the thermal relay is used for overload protection of the three-phase AC motor in the circuit. It must be pointed out that, due to the thermal inertia of the heating elements in the thermal relay, instantaneous overload protection cannot be done in the circuit, and short circuit protection cannot be done either. Therefore, it is different from overcurrent relays and fuses. According to the number of phases, there are three types of thermal relays: single-phase, two-phase, and three-phase. Each type has different specifications and model numbers according to the rated current of the heating element. Three-phase thermal relays are often used in three-phase AC motors for overload protection. Divided by function, there are two types of three-phase thermal relay. One is without phase failure protection and the other one is with phase failure protection.1.2 Protection Characteristics and Working Principle of Thermal Relay1) Protection Characteristics of Thermal Relay Because the contact action time of the thermal relay is related to the overload of the motor being protected, before analyzing the working principle of the thermal relay, the relationship between the motor's overload current and the motor's energizing time must be clarified under the condition that the motor does not exceed the allowable temperature rise. This relationship is called the overload characteristic of the motor. When an overload current occurs during the motor operation, it will inevitably cause the winding to heat up. According to the thermal equilibrium relationship, it is not difficult to draw the conclusion that under the condition of allowable temperature rise, the motor energizing time is inversely proportional to the square of its overload current. According to this conclusion, it can be concluded that the motor's overload characteristics have inverse time characteristics, as shown by curve 1 in Figure 1. Figure 1. Overload Characteristics of the Motor and Protection Characteristics of the Thermal Relay and Their Coordination In order to adapt to the overload characteristic of the motor and play the role of overload protection, it is required that the thermal relay should also have the inverse time characteristic as the motor overload characteristic. For this reason, the thermal relay must have a resistance heating element. The thermal effect generated by the overload heating current through the resistance heating element causes the sensing element to act, thereby driving the contact to complete the protection function.  The relationship between the overload current passed in the thermal relay and the action time of the thermal relay contact is called the protection characteristic of the thermal relay, as shown by curve 2 in figure 1. Considering the effects of various errors, the overload characteristics of the motor and the protection characteristics of the relay are not a curve, but a belt. Obviously, the larger the error, the wider the belt; the smaller the error, the narrower the belt. It can be known from the curve 1 in the figure that when the motor is overloaded, it is safe to work below the curve 1. Therefore, the thermal relay's protection characteristics should be close to the motor's overload characteristics. In this way, if an overload occurs, the thermal relay will operate before the motor reaches its allowable overload limit, cutting off the power to the motor to prevent damage. 2) Working Principle of Thermal Relay The heat-generating heating element in the thermal relay should be connected in series with the motor circuit. In this way, the thermal relay can directly reflect the overload current of the motor. The sensing element of a thermal relay generally uses a bimetal. The so-called bimetallic sheet is to mechanically roll two metal sheets with different linear expansion coefficients into one body. The larger the expansion coefficient is called the active layer, the smaller the expansion coefficient is called the passive layer. The bimetallic sheet undergoes linear expansion when heated. Because the linear expansion coefficients of the two layers of metal are different and the two layers of metal are closely attached together, the bimetallic sheet is bent to the passive layer side, and the mechanical force generated by the bending of the bimetallic piece drives the contact action. There are four types of bimetal heating methods, namely direct heating, indirect heating, composite heating, and current transformer heating. The direct heating type uses the bimetal as a heating element and allows current to pass through it directly; the heating element of the indirect heating type is made of resistance wire or tape, is wound around the bimetal and is insulated from the bimetal; the composite heating type is between the above two methods; the heating element of the current transformer heating type is not directly connected to the motor circuit, but is connected to the secondary side of the current transformer. This method is mostly used in situations where the motor current is relatively large to reduce the current passes through the heating element. Figure 2. Structural Schematic of the Thermal Relay The thermal element 3 is connected in series to the motor stator winding, and the motor winding current is the current flowing through the thermal element. When the motor is running normally, although the heat generated by the thermal element can bend the bimetal 2, it is not enough to make the relay operate; when the motor is overloaded, the heat generated by the thermal element increases, causing the bending displacement of the bimetal to increase.  After a certain period of time, the bimetal is bent to push the guide plate 4, and the contacts 9 and 6 are separated by the compensating bimetal 5 and the push rod 14, the contacts 9 and 6 are normally-closed contacts in which the thermal relay is connected to the contactor coil circuit, and the contactor is de-energized after being disconnected. The normally-open contacts of the contactor disconnect the power supply of the motor to protect the motor. The adjusting knob 11 is an eccentric wheel, which constitutes a lever with the support 12, and 13 is a compression spring. Turning the eccentric wheel and changing its radius can change the contact distance between the compensating bimetal 5 and the guide plate 4 so that the purpose of adjusting the setting action current is achieved. In addition, the position of the normally-open contact 7 is changed by adjusting the reset screw 8 so that the thermal relay can work in two working states: manual reset and automatic reset. When debugging the manual reset, after the fault is excluded, button 10 must be pressed to restore the movable contact to the contact position of the static contact 6. 3) Thermal Relay with Open Phase Protection One of the main reasons for a three-phase asynchronous motor to burn out is that wiring of a three-phase motor is loosened or a phase fuse is blown. If the motor protected by the thermal relay is Y connection method when one phase power failure occurs in the line, the current of the other two phases will increase a lot. Since the line current is equal to the phase current, the current flowing through the motor windings and the current flowing through the thermal relay are increased by the same proportion, so ordinary two-phase or three-phase thermal relays can protect this.  If the motor is △ connection method, the phase current and line current of the motor will not be the same when the phase failure occurs, the current flowing through the motor windings and the current flowing through the thermal relay will increase in different proportions, and the thermal element is connected in series with the power supply line of the motor, and it is set according to the rated current of the motor, that is, the line current, and the setting value is relatively large. When the fault line current reaches the rated current, in the motor winding, the fault current of the phase winding with the larger current will exceed the rated phase current, and there is a danger of overheating and burning. Therefore, the △ connection method must use a thermal relay with phase failure protection. The thermal relay with phase failure protection is a differential mechanism added to the ordinary thermal relay to compare the three currents. The structural principle of the differential phase-open protection device is shown in figure 3. The guide plate of the thermal relay is changed to a differential mechanism, which is composed of an upper guide plate 1, a lower guide plate 2 and a lever 5. They are connected by a rotating shaft. Figure 3a shows the positions of the components of the mechanism before power is applied. Figure 3b shows the position during normal energization. At this time, the three-phase bimetals are bent to the left by heating, but the bending deflection is not enough. Therefore, the lower guide plate is moved to the left for a short distance, and the relay does not operate. Figure 3c shows the situation when the three phases are overloaded simultaneously. The three-phase bimetal is bent to the left at the same time, and the lower guide plate 2 is pushed to move to the left. The normally-closed contact is immediately measured by lever 5. Figure 3 shows the disconnection of phase C.  At this time, the phase C bimetal gradually cools down, the end moves to the right and pushes the upper guide plate 1 to the right. While the temperature of the other two-phase bimetals rises, the ends are bent to the left, pushing the lower guide plate 2 to continue to move to the left. Because the upper and lower guide plates move left and right, a differential function occurs, and the normally-closed contacts are opened by the amplification of the lever. Due to the differential function, the thermal relay is accelerated to protect the motor when the phase failure occurs. Figure 3. Schematic Diagram of Differential Relay Phase Failure Protection Mechanism of Thermal Relay Ⅱ Selection and Setting Principle of Thermal Relay2.1 Thermal Relay Selection OverviewThe thermal relay is mainly used to protect the motor from overload. In order to ensure that the motor can obtain both necessary and sufficient overload protection, it is necessary to fully understand the performance of the motor, and assign it with a suitable thermal relay to perform the necessary settings. Generally, conditions related to the motor are the working environment, starting current, load nature, working system, allowable overload capacity and so on. In principle, the ampere-second characteristic of the thermal relay should be as close as possible or even overlap the motor's overload characteristic, or under the motor's overload characteristic, and at the same time, the thermal relay should not be affected (not actuated) at the moment when the motor is temporarily overloaded and started. The correct selection of the thermal relay is closely related to the working system of the motor. When the thermal relay is used to protect the motor for long-term or intermittent long-term operation, it is generally selected according to the rated current of the motor. For example, the setting value of the thermal relay may be equal to 0.95-1.05 times of the rated current of the motor, or the median value of the setting current of the thermal relay is equal to the rated current of the motor, and then adjust. When the thermal relay is used to protect a motor that is repeatedly operated for a short time, the thermal relay has only a certain range of adaptability. If there are many operations per hour, a thermal relay with a speed saturation current transformer must be selected. For special working motors with frequent forward and reverse phase on and off, it is not appropriate to use thermal relays as overload protection devices. Instead, use temperature relays or thermistors embedded in the motor windings to protect them.2.2 Type Selection of Thermal RelayThe thermal relay can be divided into the two-pole types and three-pole types from the structural type. The three-pole type is divided into phase-open protection and no phase-open protection, which should be selected according to the stator wiring of the protected motor. When the motor stator winding is in delta connection, a three-pole thermal relay with phase failure protection must be used; for a motor using the star connection method, a thermal relay without phase failure protection is generally used. Because the general motor does not have a neutral wire when using the star connection method, the two-pole or three-pole type of the thermal relay can be used. However, if the motor is set to use a star connection method with a neutral wire, the thermal relay must use a three-pole type. In addition, generally a two-phase structure thermal relay should be selected for light-load starting, long-term working motors or intermittent long-term working motors; when the current and voltage balance of the motor is poor, the working environment is poor, or there are fewer people to look after, three-phase thermal relay can be used.2.3 Selection of Rated Current of Thermal Relay1) Ensure the normal operation and starting of the motorIn the case of normal starting current and starting time and infrequent starting, it must be ensured that the starting of the motor does not cause the thermal relay to malfunction. When the starting current of the motor is 6 times the rated current, the starting time does not exceed 6s, and rarely starts continuously, the thermal relay can generally be selected according to the rated current of the motor. (In practice, the rated current of the thermal relay can be slightly larger than the rated current of the motor) 2) Consider the object of protection-the characteristics of the motorModels, specifications, and characteristics of motors. The insulation materials of motors are classified into A, E, and B grades. Their allowable temperature rises are different, so their ability to withstand overload is also different, which should be paid attention to when selecting a thermal relay. In addition, the open-type motor is easier to dissipate heat, while the closed-type motor is much more difficult to dissipate heat. With a slight overload, its temperature rise may exceed the limit. Although the selection of the thermal relay is based on the rated current of the motor in principle, the rated current of the thermal relay (or thermal element) that it is equipped with should be appropriately small for the motor with poor overload capacity. In this case, the rated current of the thermal relay (or thermal element) can also be taken as 60% -80% of the rated current of the motor. 3) Consider load factorsIf the nature of the load is not allowed to stop, even if the overload will shorten the life of the motor, the motor should not be allowed to trip unexpectedly, so as not to suffer a huge loss many times higher than the price of the motor. At this time, the rated current of the relay can be selected to a larger value (of course, the selection of the motor under this working condition generally also has a strong overload capacity). In this case, it is best to use the protective measures of the organic combination of thermal relays and other protective appliances, and only consider tripping when a very dangerous overload occurs. In short, this is not a dogmatic formula and should be considered comprehensively. 2.4 Selection of Thermal Element Setting CurrentAccording to model number of the thermal relay and the rated current of the thermal element, the adjustment range of the setting current of the thermal element can be found out. Generally, the setting current of the thermal relay is adjusted to the rated current of the motor; for motors with poor overload capacity, the setting value of the thermal element can be adjusted to 0.6-0.8 times of the rated current of the motor; when the motor starts for a long time, drags the impact load or is not allowed to stop, the setting current of the thermal element can be adjusted to 1.1-1.15 times of the rated current of the motor. 2.5 Reliable and Reasonable Protection Characteristics of The Thermal RelaySpecifically, it should have an inverse time characteristic similar to the allowable overload characteristic of the motor, and it should be below the allowable overload characteristic of the motor, and it should have high accuracy to ensure the reliability of the protective action. 2.6 Other Considerations1) Operating frequency: When the operating frequency of the motor exceeds the operating frequency of the thermal relay, such as the motor's reverse braking, reversible operation, and dense on-off, the thermal relay cannot provide protection. At this time, you can consider using a semiconductor temperature relay for protection. 2) It is not necessary to set overload protection for motors with short working hours and long intervals (such as rocker lifting motors for rocker drilling machines, etc.), and motors that have little possibility of overload despite long-term work(such as exhaust fans, etc.). 3) Thermal relays are generally not suitable for motors with a jog, heavy load starting, continuous forward and reverse rotation, and reverse braking. 4) It should have a certain temperature compensation: due to the change in the temperature of the surrounding medium, under the same overload current, the operation of the thermal relay will cause an error. To eliminate this error, temperature compensation measurements should be set up. 5) In general, the principle that the protected motor should not restart automatically even after the thermal relay is automatically reset after the thermal relay protection action, otherwise, the thermal relay should be set to the manual reset state. This is to prevent the motor from being repeatedly restarted several times to damage the equipment before the fault is eliminated.  For example: Generally, for the control circuit using button control to manually start and stop, the thermal relay can be set to the automatic reset form; for the automatic start circuit using automatic component control, the thermal relay should be set to the manual reset form; Any thermal relay that can be automatically reset should be able to be automatically reset reliably within 5 minutes after operation, while the manual reset one should be reset reliably when the manual reset button is pressed by hand within 2 minutes after the operation. Most products generally have both manual and automatic reset methods and can be adjusted to any method with screws to meet the needs of different occasions. 6) The operating current value should be adjustable to meet the needs in production and use, and reduce the specification-grade, so the thermal relay of a certain specification should be able to be realized by adjusting the cam. 7) Since it takes time for the thermal element to deform due to heat, the thermal relay can only be used as overload protection for the motor, not as short circuit protection. Therefore, when using a thermal relay, a fuse should be installed as short circuit protection. For heavy load, frequent-starting large-capacity important motors, overcurrent relays (time-delay action type) can be used for its overload and short circuit protection. Ⅲ Other Matters Needing Attention3.1 Installation DirectionThe installation direction of the thermal relay is easily overlooked. In the thermal relay, there is a current that generates heat through the heating element, which promotes the action of the bimetal. There are three ways of heat transfer: convection, radiation and conduction. Convection is directional, and heat is transferred from the bottom up. During the placement, if the heating element is under the bimetal, the bimetal will heat up quickly and the action time will be short; if the heating element is next to the bimetal, the bimetal will heat slowly and the action time of the thermal relay will be long.  When the thermal relay is installed with other electrical appliances, it should be installed below the electrical appliances and away from other electrical appliances by more than 50 mm to avoid the influence of other electrical appliances. The installation direction of the thermal relay should be in accordance with the specifications of the product manual to ensure that the thermal relay's operating performance is consistent during use.3.2 Selection of Connecting WiresThe connecting wires at the output end should be selected according to the rated current of the thermal relay. Too thick or too thin will also affect the normal operation of the thermal relay. If the connecting wire is too thin, the heat generated by the connecting wire will be transferred to the bimetallic sheet, and the heat-generating component will dissipate less heat along the wire, which shortens the trip time of the thermal relay.  On the contrary, if the connecting wire is too thick, this will extend the trip time of the thermal relay. For thermal relays with a rated current of 10 A, the cross-sectional area of the connecting wire at the output end is preferably 2.5 mm2 (single-strand copper-core plastic wire), the one of 20 A is preferably 4 mm2 (single-strand copper-core plastic wire), 16 mm2 is suitable for the one of 60 A(multi-strand copper-core rubber flexible wire), and the one of150 A is preferably 35 mm2 (multi-strand copper-core rubber flexible wire).  Because the material and thickness of the wire will affect the heat conduction from the termination of the thermal element to the external heat, if the wire is too thin, the axial thermal conductivity is poor, and the thermal relay may act in advance; if the wire is too thick, the axial heat conduction is fast, and the thermal relay may lag behind. The connecting wire at the output end of the thermal relay is generally a copper core wire. If an aluminum core wire is used, the cross-sectional area of the wire should be increased by 1.8 times, and the end of the wire should be tinned. Reference table for selection of cross-section of connecting wire:Setting current of thermal relay I / ACross-sectional area of connecting wire MM20 < IN ≤81.08 < IN ≤121.512 < IN ≤202.520 < IN ≤254.025 < IN ≤326.032 < IN ≤5010.050 < IN ≤6516.065 < IN ≤8525.085 < IN ≤11535.0115 < IN ≤15050.0150 < IN ≤16070.03.3 Use EnvironmentThis mainly refers to the ambient temperature, which has a greater impact on the speed of the thermal relay. The temperature of the medium surrounding the thermal relay should be the same as the temperature of the medium surrounding the motor, otherwise, the adjusted fit will be destroyed. For example: when the motor is installed in an environment of high temperature and the thermal relay is installed in an environment of lower temperature, the action of the thermal relay will lag (or the action current is large); otherwise, its action will be advanced (or the action current is small). For thermal relays without temperature compensation, they should be used at the place where there is little difference in an ambient temperature between the thermal relay and the motor. For the thermal relay with temperature compensation, it can be used in the place where the environmental temperature of the thermal relay and the motor is different, but the influence caused by the environmental temperature change should be minimized as much as possible. The ambient temperature of the thermal relay and the protected motor should be considered. When the ambient temperature of the thermal relay is lower than the ambient temperature of the protected motor by 15℃, a thermal relay with a larger rated current rating should be used; when the ambient temperature of the thermal relay is lower than the ambient temperature of the protected motor by 15℃, a thermal relay with a smaller rated current rating should be used. In addition, the load of the motor and the adjustment range that the thermal relay may require should also be considered.3.4 Adjustment of Thermal RelayBefore putting it into use, the setting current of the thermal relay must be adjusted to ensure that the set current of the thermal relay matches the rated current of the protected motor. Before the thermal relay is used in the circuit, the specific current of the thermal relay must be adjusted according to the rated current of the motor to meet the requirements of corresponding occasions. For example, for a 10kW, 380V motor with a rated current of 19.9A, a XX20-25 thermal relay can be used. The setting current of the thermal element is 17 ～ 21 ～ 25A. First, set it at 21A according to the general situation. If it is found that it often moves in advance and the temperature rise of the motor is not high, you can change the setting current to 25A and continue to observe; if the motor temperature rises at 21A, and the thermal relay lags, you can change the setting current to 17A and observe to get the best fit. It is used to adjust the rated current when overload protection of the motor is repeatedly operated for a short time. Multiple tests and adjustments in the field can get more reliable protection. The method is: first adjust the rated current of the thermal relay to be slightly smaller than the rated current of the motor. If it is found that it often moves during operation, then gradually increase the rated value of the thermal relay until it meets the operating requirements. There should be motor protection during the special operations. Motors with forward, reverse, and frequent on-off operations should not be protected by thermal relays. The ideal method is to protect it with a temperature relay or thermistor embedded in the winding.  Ⅳ Frequently Asked Questions about Thermal Relay1. What is a thermal relay?A relay that opens or closes contacts with a bending mechanism as a result of the difference in the expansion coefficients of a bimetal, which is heated by the current. ... The thermal relay is combined with a magnetic contactor because it cannot switch the main circuit by itself. The operating point can be changed. 2. How does a thermal relay work?A thermal relay works depending upon the above-mentioned property of metals. The basic working principle of thermal relay is that, when a bimetallic strip is heated up by a heating coil carrying overcurrent of the system, it bends and makes normally open contacts. 3. What is the purpose of thermal overload relay?Thermal overload relays are economic electromechanical protection devices for the main circuit. They offer reliable protection for motors in the event of overload or phase failure. The thermal overload relay can make up a compact starting solution together with contactors. 4. What are the two types of thermal overload relays?Thermal Overload RelaysThermal overloads can be divided into two types: solder melting type, or solder pot, and bimetal strip type. Because thermal overload relays operate on the principle of heat, they are sensitive to ambient (surrounding air) temperature. 5. How do you use a thermal overload relay?Overload relays protect a motor by sensing the current going to the motor. Many of these use small heaters, often bi-metallic elements that bend when warmed by the current to the motor. When the current is too high for too long, heaters open the relay contacts carrying current to the coil of the contactor. 6. How do you test a thermal overload relay?CEP7 Overload Relay test procedures:Measure the normal motor running current (i motor).Turn off the motor and let it cool for about 10 minutes.Calculate the following ratio: i (motor) / i (overload min FLA).Set the overload to its minimum FLA and turn on the motor.Wait for the overload to trip. 7. What is thermal overload relay how it functions?The function of a thermal overload relay, used in motor starter circuits is to prevent the motor from drawing excessive current which is harmful to motor insulation. It is connected either directly to motor lines or indirectly through current transformers. 8. What is the purpose of a thermal overload?Thermal overload relays are protective devices. They are designed to cut power if the motor draws too much current for an extended period of time. To accomplish this, thermal overload relays contain a normally closed (NC) relay. 9. What does a thermal overload relay consist of?Bimetallic thermal overload relays (sometimes referred to as heater elements) are made of two metals, with different coefficients of thermal expansion, that is fastened or bonded together. A winding, wrapped around or placed near the bimetallic strip, carries current. 10. How do I know if my overload relay is bad?Unplug the start relay from the compressor and give it a shake. If you can hear rattling on the inside of the start relay, then the part is bad and will have to be replaced. If it's not rattling and appears to be in good condition, you may have a problem with the actual compressor. 

Ⅰ IntroductionA differential transformer is an electromagnetic inductive displacement sensor that converts mechanical displacement into an electrical signal. It mainly relies on the displacement of the movable iron core in the cylindrical coil and establishes a mutual induction relationship between the input coil and the output coil of the cylindrical coil, and the displacement of the movable core can be obtained by measuring the induced voltage of the output coil proportional to it.  CatalogⅠ IntroductionⅡ The Working Principle and Structure of the Differential TransformerⅢ The Type of Differential TransformerⅣ Linearity and SensitivityⅤ The Cause of the ErrorⅥ The Measurement Circuit  6.1 Differential DC output circuit  6.2 DC differential transformer circuitⅦ The Application of Differential TransformerⅧ Application Circuit Examples of Differential Transformer  8.1 MZK-4R Grinding Machine Automatic Control Device  8.2 ZD41B Short Cylindrical Roller Sorting Machine  8.3 Discussion of Differential Transformer ApplicationⅨ FAQ Characteristics of Differential Transformer(1) There are many types of linear ranges, and it is easy to select according to the use. Usually, there are about 10 types between ±2 mm and ±200 mm.(2) The structure is simple, so the vibration resistance and impact resistance are strong.(3) It does not wear, does not deteriorate, and has excellent durability.(4) The output voltage has a precise ratio to the displacement of the core, that is, the linearity is good. Generally, the full stroke deviation of this sensor is less than 1%, and it can be guaranteed to be ±0.2% to ±0.3% in high-grade products.(5) Because of the high sensitivity, a large output voltage can be obtained, and a small displacement can be detected without requiring an advanced circuit.(6) Since the output changes smoothly, high-resolution detection is possible.(7) The zero point is stable, and its use as a reference point for measurement is good for maintaining accuracy.(8) A high response speed from 500 Hz to 100 Hz can be obtained. Ⅱ The Working Principle and Structure of the Differential TransformerThe structure of the differential transformer is divided into two types: variable-gap type and solenoid type. Since the variable-gap type differential transformer has a small stroke and a complicated structure, it is rarely used at present, and the solenoid type is usually adopted. The basic components of the solenoid type differential transformer include an armature, a primary coil, a secondary coil, and a coil frame. The primary coil acts as excitation and corresponds to the primary side of the transformer. The secondary coil is formed by inverting two coils of the same structural size and parameters to form the secondary side of the transformer. There are two-section, three-section and multi-section according to the initial and secondary arrangement. The zero potential of the three-section is small, the two-section is more sensitive than the three-section, and the linear range is large. The four-section and five-section are all efforts to improve the linearity of the sensor. The working principle of the differential transformer can be explained by the principle of the transformer. The difference is: the general transformer is the closed magnetic circuit, and the differential transformer is the open magnetic circuit; the mutual inductance of the original transformer and the secondary side is constant, and the mutual inductance between the primary and secondary sides of the differential transformer changes as the armature moves. The operation of the differential transformer is based on the change of mutual inductance. The construction principle of the differential transformer is as shown in figure 1, and is composed of a cylindrical coil and a core that is completely separated from it. A typical differential transformer has three cylindrical coils, each of which is one-third of the total length, with a primary coil in the middle and a secondary coil on each side. The iron core added to the cylindrical coil is used to link the magnetic lines of force in the coil to form a magnetic circuit. Figure 1. The Construction Principle of the Differential Transformer When an alternating voltage is applied to the primary coil in the middle (ie, excitation), an electromotive force is generated due to the mutual inductance with the coils at both ends (this is the same as that of a normal transformer). Since the secondary coils are connected in series with each other in opposite polarity, the induced electromotive forces in the two secondary coils are opposite in phase, and as a result of the addition, a potential difference between the two is generated at the output end. At the center of the coil length direction, the induced voltages of the two secondary coils are equal in opposite directions, and thus the output is zero. This position is called the mechanical zero point of the differential transformer (or simply zero points). When the iron core changes position from zero points to a certain direction, the voltage of the secondary coil in the displacement direction increases, and the voltage of the other secondary coil decreases. The product design guarantees that the potential difference is proportional to the displacement of the core. When the iron core moves from zero points to the opposite direction, a proportional voltage is generated, but the phase is 180° different from the previous one. The relationship between the secondary coil voltage and the output voltage difference with respect to the core displacement is shown in figure 2. The range in which the voltage difference is proportional to the core displacement is called the linear range, and its proportionality is called linearity, which is the most important indicator of the differential transformer. Figure 2. The Core Displacement — Output Relationship of Differential Transformer Ⅲ The Type of Differential TransformerThe standard differential transformer consists of a cylindrical coil and a rod-shaped iron core. In actual use, there is also a structure with a guide and a spring. The basis for the classification of differential transformers is as follows: • According to the voltage input to the primary coil(excitation type)Commercial power supply type is suitable for practical measuring instruments of 50-60Hz, 6.3V power supply excitation;Oscillation power supply type is an excitation circuit of 1~5KHz, it is suitable for application measuring instruments requiring certain accuracy and response characteristics;DC power supply type, the semiconductor device is installed in the coil part of the differential transformer to form the excitation oscillation circuit and the secondary output detection circuit inside the coil. It is a differential transformer whose input and output are both DC, called DC-DT. • According to the displacement range of the iron core (displacement type)Small displacement type considers how to measure the small displacement below 0.5mm from the structure;General displacement type is designed for measuring the displacement about 100mm or less;The long-stroke type is designed for long stroke measurement of 120 to 400 mm.  • According to the use environment (environment type)Standard type is used in a normal environment with a temperature of -30℃ to +90℃ and a humidity of about 80%;Environmentally friendly type is the sensor for high temperature, high humidity, waterproof and radioactive environments. Features and SpecificationsWhen using a differential transformer as a position sensor, the selected specifications are as follows:◆ Excitation power supply (frequency, voltage, waveform, etc.);◆ Structure (whether guides and springs are required);◆ Linear range (it is usually ±1%, and that of high-grade products is ±0.5%～±0.2%);◆ Sensitivity (corresponding to the output of the core displacement of 1mm);◆ Impedance (input, output impedance);◆ Connection conditions (cables, sockets, input circuits, etc.);◆ Assembly method (connection method with the object to be tested, etc.);◆Environmental conditions (temperature, humidity, dust, water resistance, rust-proof conditions, etc.). Ⅳ Linearity and Sensitivity• Linearity. The linear range of the differential transformer is affected by the non-uniform magnetic field of the solenoid coil. A reasonable design guarantees the required linear range and linearity.• Sensitivity. The sensitivity of the differential transformer refers to the change of the output potential generated by the armature unit displacement. It can be expressed by mV/mm. In practice, considering the influence of the excitation voltage, it is also commonly expressed by mV/mm/V, that is, the potential change generated by the armature unit displacement divided by the excitation voltage value. The sensitivity of the differential transformer is related to the primary voltage, the number of secondary winding turns, and the frequency of the excitation voltage:• Relationship with secondary turnsThe number of secondary turns increases and the sensitivity increases, which is linear. However, the number of secondary turns cannot be increased indefinitely because the residual voltage at the zero points of the differential transformer also increases.• Primary voltageThe sensitivity is proportional to the primary voltage, but the primary voltage should not be too large. When the voltage is too large, the differential transformer coil will heat up and cause the output signal to drift. Generally, 3~8V is used.• Excitation power frequencyWhen the frequency is very low, the sensitivity increases with increasing frequency; when the frequency increases, the inductance of the coil is much higher than its resistance, the sensitivity is independent of the frequency; when the frequency exceeds a certain value (the value varies depending on the armature material), the effective resistance of the wire increases due to the skin effect of the wire at a high frequency, and the eddy current loss and hysteresis loss of the armature increase, and the output decreases. Figure 3 is the relationship between the input frequency and sensitivity of a certain magnetically permeable material, which can be used as a reference for selecting the excitation frequency. Figure 3. Relationship Between Excitation Frequency and Sensitivity of Differential Transformer Ⅴ The Cause of the ErrorThe error refers to the deviation between the actual and ideal characteristics of the sensor. Here, the system error inherent in the sensor itself and random error is mainly analyzed, and the error in the measurement method is not involved.• Influence of amplitude and frequency of excitation power supplyFluctuations in the magnitude of the excitation supply voltage cause changes in the strength of the excitation field of the coil to directly affect the output potential. The frequency fluctuations have little effect.• The effect of temperature changesChanges in ambient temperature cause changes in the magnetic permeability of the coil and the magnet, causing a change in the magnetic field of the coil to cause temperature drift. This effect is more severe when the coil quality factor is low. The use of constant current source excitation is more advantageous than the constant voltage source. Properly increasing the quality factor of the coil and using a differential bridge can reduce the effects of temperature.• Zero residual voltageWhen the armature of the differential transformer is in the neutral position, the ideal output voltage should be zero. But in fact, when using a bridge circuit, there is always a small voltage value (from a few millivolts to tens of millivolts) at zero point, which is called the zero residual voltage. Figure 4 is an enlarged output characteristic of the zero residual voltage. The dotted line is the ideal characteristic and the solid line indicates the actual characteristics. The presence of a zero residual voltage causes an insensitive zone near the zero point. Figure 4. Zero Residual Voltage of the Differential TransformerThe waveform of the zero residual voltage is very complicated and irregular. It is analyzed to include the fundamental wave in-phase component, the fundamental wave orthogonal component, and the second and third harmonics as well as the electromagnetic interference waves with small amplitude. The reasons why the zero residual voltage is generated are as follows:• Fundamental wave component: Since the winding of the two secondary windings of the differential transformer can not be completely identical in process, its equivalent circuit parameters (mutual inductance, self-inductance and loss resistance, etc.) cannot be completely equal, thus two induced potential values are not equal. The copper loss resistance of the primary coil, the iron loss and material non-uniformity of the magnetically permeable material and the presence of the inter-turn coil capacitance cause the excitation current to be out of phase with the generated magnetic flux.The above factors cause the induced potentials in the two secondary coils to be not only unequal in value but also in phase. The zero residual voltage generated by the difference in phase cannot be eliminated by adjusting the armature displacement. • High-order harmonics: The high-order harmonics are mainly caused by the nonlinearity of the magnetization curve of the magnetically permeable material. Due to the effects of hysteresis loss and magnetic saturation, the excitation current is inconsistent with the magnetic flux waveform, resulting in a non-sinusoidal wave (mainly the third harmonic flux), thereby inducing a non-sinusoidal potential in the secondary winding. The general method for eliminating zero residual voltage:— From the design and process, try to ensure the symmetry of the coil and the magnetic circuit. The structure can adopt the magnetic circuit adjustment mechanism; when selecting the working point of the magnetic circuit, it should be ensured that the magnetic field does not work in the saturation region of the magnetization curve.— Use the appropriate measurement line. The phase-sensitive detection circuit can not only identify the moving direction of the armature but also eliminate the high-order harmonic zero residual voltage of the armature in the middle position. As shown in figure 5, after using the phase-sensitive detection, the characteristic curve of the armature reverse stroke changes from 1 to 2, thereby eliminating the zero residual voltage. Figure 5. Output Characteristics After Phase-sensitive Detection— Use compensation lines. In applications of a differential transformer, there are many circuit types used to eliminate the zero residual voltage, which can be summarized as follows:▲Add series resistors to eliminate the in-phase component of the fundamental wave; generally the resistance of the series resistor is very small such as 0.5~5Ω, and is wound with constant wire.▲Add parallel resistors to eliminate the fundamental wave orthogonal component, but it has an effect on the in-phase component of the fundamental wave; the resistance of the shunt resistor is from tens to hundreds of kiloohms.▲Shunt capacitor, change phase shift, and compensate for high-order harmonics; parallel capacitor value is in the range of 100 ~ 500pf.▲Add feedback winding and feedback capacitor to compensate for fundamental wave and high-order harmonics.In fact, these values are determined experimentally; based on the working principle of the differential transformer and the cause of the zero residual voltage, the above methods can be modified and combined, and it is also possible to design a new compensation circuit. Figure 6 shows some line schematics for compensating for zero residual voltage for reference. Figure 6. Zero Residual Voltage Compensation Circuit of Differential Transformer Ⅵ The Measurement Circuit6.1 Differential DC output circuitThe output voltage of the differential transformer is an AC signal whose amplitude is proportional to the armature displacement. If the output value is measured with an AC voltmeter, it can only reflect the magnitude of the armature displacement and cannot reflect the direction of the displacement. Secondly, there is a certain zero residual voltage in the AC voltage output. Even with various compensation methods, it can only be reduced and cannot be completely eliminated. Therefore, the DC output circuit is commonly used in engineering practice, which can reflect the displacement direction of the armature and compensate for the zero residual voltage. The DC output circuit has two forms: one is a differential phase-sensitive detector circuit, and the other is a differential rectifier circuit.The differential rectifier circuit is shown in Figure 7. This circuit is relatively simple. It does not need to compare the voltage windings. It does not need to consider the influences if the phase adjustment and the zero residual voltage. The influence on the sensing and distributed capacitance can also be ignored. In addition, since the rectifying portion is on the differential output side, the two DC conveying lines are convenient to connect, and can be transported at a long distance, and are widely used. Figure 7. Differential Rectifier Circuita) full-wave current output         b) half-wave current outputc) full-wave voltage output         d) half-wave voltage outputDifferential phase sensitive detector circuits come in many forms. Figure 8 shows two examples, one is a full wave circuit and the other is a half-wave circuit. The phase sensitive detector circuit requires that the comparison voltage and the secondary transformer output voltage of the differential transformer have the same frequency and the same phase or opposite phase.  To ensure this, a phase-shifting circuit is usually connected to the circuit. In addition, it is required that the comparison voltage amplitude should be as large as possible (because the comparison voltage acts as a switch in the detector circuit, and if it is less than the signal voltage, the switch cannot be turned on), generally it should be 3 to 5 times the signal voltage. In the figure, Rw is the bridge zero potentiometer. For the case of measuring small displacements, since the output signal is small, the input amplifier is also connected to the circuit. Figure 8. Differential Phase-sensitive Detection Circuita) full-wave detection         b) half-wave detection6.2 DC differential transformer circuitThe working principle of the DC differential transformer is exactly the same as that of the ordinary differential transformer described above. The only difference is that the power supply used in the instrument is a DC power supply (dry battery, battery, etc.). The schematic diagram of the DC differential transformer is shown in figure 9. It consists of a DC power supply, a multivibrator, a differential rectifier circuit, a filter and so on. Figure 9. Schematic Diagram of DC Differential Transformer CircuitThe multivibrator provides a high frequency excitation power supply for the differential transformer, which can be a square wave, a triangular wave or a sine wave. DC differential transformers are commonly used in the following applications:◆ The measuring point is far from the control room (more than 100m);◆ Simultaneous use of multiple differential transformers and requires no interference with each other and with other equipment;◆ Where explosion protection is required;◆ Requires easy to carry, such as working in the field. Ⅶ The Application of Differential TransformerDisplacement measurement is the most important use of differential transformers. Any physical quantity that can be transformed into a displacement can be measured with a differential transformer. It is noted that the differential transformer measurement is generally contact type. In some cases, it will affect the state of the measured object (such as vibration), which is the so-called “load effect”. In this case, other types of sensors must be used such as eddy current sensors, etc.◆ It can be used as the main component of many precision measuring instruments, such as making high-precision inductance comparator with corresponding measuring devices, which can perform various precise measurements on parts: length, inner diameter, outer diameter, non-parallelism, non-flatness, non-perpendicularity, vibration, eccentricity, and ellipticity.◆ As the main measuring part of the bearing rolling element automatic sorting machine, it can sort large and small steel balls, large and small cylinders, large and small round vertebrae, needle roller and so on.◆ It is used to measure the expansion, elongation, strain, movement, etc. of various parts. With a variety of sensors, its displacement measurement range can be from ±3μm to over 1000mm.◆ Vibration and acceleration measurements. An accelerometer for measuring vibration can be constructed by using a differential transformer and a cantilever beam elastic support.◆ Pressure measurement. The differential transformer and the elastic sensitive component (diaphragm, bellows, spring tube, etc.) can be combined to form a pressure sensor of the open-loop system and a force-balanced pressure gauge of the closed-loop system. Due to the excellent characteristic of differential transformer as the displacement sensor, it has been applied in almost all industrial fields and several specific examples are described below.• Steel industry: blast furnace top-level detection, continuous casting roll gap, sand type vibration, convexity detection, position detection of sliding water nozzles such as ladle and tundish.• Heavy motor industry: the main valve of the steam turbine, the valve lift detection of the bypass valve, and the posture monitoring of the elevator.• Construction machinery industry: Measuring head for numerical control machine tool simulation test.• Ceramic industry: thermal expansion testing of refractory materials, shape detection of templating glass.• Ship and vehicle industry: fuel classification position detection of diesel engine, dynamic characteristic detection of fuel injection valve of an automobile engine, and eccentricity detection of tire and wheel.• Weighing machine industry: a device that automatically measures the weight of the bag, and a weighting machine for the asphalt carrying device.• Measuring instrument, testing machine industry: used for traction test, creep test of metal materials and plastics, signal conversion part of flow meter and liquid level meter, a mechanical test of civil building components.• General industry: spacer separators for assembling bearings, motion deviation detection during stamping, and measurement of workpiece size and shape deviation. Ⅷ Application Circuit Examples of Differential Transformer8.1 MZK-4R Grinding Machine Automatic Control DeviceThis device is used on automatic or semi-automatic grinding machines. During the grinding process of the workpiece, the control device can accurately output 4 signals according to the amount of the pre-regulation to control the introduction of the grinding head, rough grinding, fine grinding, light grinding and exit, etc., thus realizing the automatic measurement and control of the grinding process. • Working process of the grinding machineWhen the workpiece is loaded, the measuring device first enters the workpiece for measurement. If the workpiece size meets the pre-adjusted result, the control device sends a “starting” signal, the grinding head enters the workpiece and moves forward quickly to the machining direction, and coarse grinding starts. Taking the internal grinding as an example, as the workpiece size of the grinding wheel becomes smaller, the output signal of the measuring head also becomes smaller.  When the preset position is reached, the trigger sequentially sends three signals, that is, the “rough grinding end” signal, indicating that the rough grinding is finished, so that the moving speed of the grinding wheel is reduced, and the fine grinding starts; when the fine grinding is finished, the “finishing end” signal is issued, so that the grinding wheel stops moving and the light grinding starts; when the preset size is reached, the “light grinding end” signal is issued to make the grinding wheel and the detection device exit quickly. • Working principle of measuring head (sensor)The measuring head adopts a differential transformer type displacement sensor, and its structure is as shown in figure 10(a). The iron core moves to the right, so that the induced potential of the winding A decreases, and the induced potential of the winding B increases (and vice versa). The two windings and the resistors R1 and R2 in the measuring device form a bridge to realize differential output, as shown in figure 10(b). Figure 10. Schematic Diagram of the Differential TransformerThe primary coil is excited by a square wave generator with a square wave frequency of 3 kHz and an effective voltage value of 3.5V. Along with the change of the displacement of the core, a corresponding voltage variable is generated between the boom of the potentiometer Rw and the secondary common tap (ground) of the measuring head. The displacement-voltage characteristic curve in figure 11 is obtained after the voltage variable is amplified and phase-sensitive rectified. Figure 11. Output Characteristic Curve of Differential TransformerIn the figure, the S-T segment is the full linear range, wherein the H-E segment (high precision) is the ×1 gear indication range, and the K-C segment (low precision) is the ×10 gear indication range. The“start”signal 0 is sent in the D-A segment, the“rough grinding end” signal 1 is sent in the G-B segment, and the“fine grinding end” signal is 2 sent in the 0-F segment. The“light grinding end”signal 3 is sent at point 0. • Principle of the circuit①The circuit block diagram shown in figure 12. Figure 12. Circuit Block Diagram of Control Device②Explanation of the circuit principleThe device consists of six parts: ▲Input bridge, the two arms are composed of two secondary windings of the measuring head, the other two arms are composed of R84 and R85, the potentiometer VR1 is used for the electrical zero points coarse adjustment, the VR2 is used for the zero points fine adjustment, and the R86 is used to limit the zero point adjustment range.In order to obtain the reference voltage for amplifier calibration, a voltage is obtained by the square wave generator, and another bridge is formed by transformers TR4, R88, and R89, and VR4 is used to adjust the reference voltage. ▲The amplifier amplifies the weak signal obtained in the input circuit to have sufficient amplitude to complete the measurement and control. T15, T17, and T18 form a voltage amplifier with gains of about 10, 20, and 20 dB, respectively. T16 is a buffer stage. T19 and T20 form a push-pull power amplifier stage, and the voltage gain of the amplifier is about 60 to 70 dB. In order to achieve higher stability and linearity, deeper negative feedback is added to each stage. The negative feedback of first stage is adjustable, and the total gain of the amplifier is adjusted by VR3. ▲Phase-sensitive rectification and indicating circuit are used to complete the rectification and identify the phase of the input signal. The half-wave rectification circuit is composed of D15 and D16, and the blocking voltage is 13V, which is provided by the square wave generator.The rectified DC ramp signal is used as an input to the trigger on the one hand and as a panel indicator on the other. The μ meter is a microampere meter with a full-scale of 150μA, and full-scale indications of 50μ and 500μ are obtained with shunt resistors R90 and R91. D33 is used as a voltage clamp to protect the meter head. ▲Square wave generator, which is used to generate the excitation voltage required by the measuring head and the blocking voltage required for phase-sensitive rectification. The high rectangular coefficient multivibrator circuit is composed of T21 and T22, which is easy to start, high in frequency and amplitude stability, and its oscillation frequency is 3 to 3.5 kHz. ▲Trigger, according to the comparison of the output voltage of the phase-sensitive rectification and the pre-adjustment voltage, four different control signal outputs are sequentially generated. The circuit adopts a trigger with an emitter coupled by a Zener tube, which has a small temperature drift and convenient backlash adjustment. Among them, VR5, VR6, VR7, and VR8 are used as the adjustment potentiometers for the four signals of “0”, “1”, “2”, and “3” on the panel. ▲Power:-24V, used for power relay after rectification and filtering;-15V, generated by the series regulator circuit and is used as the collector voltage of each transistor and the trigger pre-call;+6V, generated by the shunt regulator circuit and is supplied for the bias and pre-call of the trigger. • Main technical indicators✿ Instrument indexing and error:High precision (G) 1μ/division; full scale -10～+50μ; error ≤1.5μLow precision (D) 20μ/division; full scale -100～+500μ; error ≤30μ✿ Adjustable range of control signal :Signal "0", 350～500μ;Signal "1", 30～100μ;Signal "2", 0 ~ 30μ;Signal "3", -10 ~ +10μ✿ Electrical zero adjustable range:Not less than 100μ, and ±5μ fine adjustment✿ Repeat error:No more than 1μ✿ (Grid) voltage adjustment error:No more than 3μ✿ Instability:Time drift is no more than 10μ/4 hours; temperature drift is no more than 10μ/ 10℃ 8.2 ZD41B Short Cylindrical Roller Sorting MachineThis machine is composed of high-precision micrometer (differential transformer), combined with transistor circuit to form measurement and logic control device to complete the task of automatically sorting short cylindrical bearing rollers. • Main technical indicators◆ Measurement range:length is no more than 15mm5 to 15 mm in diameter◆ Accuracy:1μ, 2μ, 3μIf the magnification and radial grouping potentiometer are re-tuned, any grouping in the range of 0.5 to 5μ can be obtained.◆ Number of groups:10 groups.◆ Speed:28/min to 65/min,can be adjusted arbitrarily • Working principleThe measurement and classification of the radial dimensions of the roller are automated. The roller to be tested is manually placed in a disc-shaped hopper, passed through the vibrating roller to the feeding position along the pipe, and then pushed into the measuring portion by the reciprocating push rod for radial measurement. When different sizes of rollers enter the measurement site for measurement, the differential transformer guide core is displaced in the coil, so that the differential transformer outputs an alternating current signal proportional to the change in the size of the roller, and tiny electrical signal is amplified, rectified, and then amplified by the DC amplifier, so that the corresponding trigger drives the relay and the electromagnet to open the storage valve of the sorting group, so that the measured rollers of different diameters are placed in different sorting bins for automated measurement and sorting. Here we mainly introduce the radial dimension measurement part, namely the differential transformer and its secondary circuit. The measuring part of the roller consists of a differential transformer, a 4KHz oscillator, an attenuator, a low-frequency AC amplifier, a phase-sensitive rectification, a DC amplifier, a regulated power supply, etc. ① Micrometer (differential transformer): The differential transformer is used to convert the diameter of the roller into a change in the amount of electricity. The primary coil is excited by a rectangular wave with a frequency of 4 kHz and an amplitude of 2 to 3 volts. Thus, the voltages of u2 and u3 are induced in the secondary coil. The different names of the secondary coils are connected as a common point ground, and the other ends serve as a differential output and form a bridge balance loop with the resistors R1, R2 and the potentiometer VR.  When the iron core is at the center position of the two secondary coils, since the magnetic resistance of the two coils is equal, the bridge is in a balanced state, and the differential transformer output E2=0 (u2=u3). In a static state, due to the self-weight of the iron core and the guide rod, the iron core is located at the lowermost end of the secondary coil, thus outputting a negative polarity voltage; when the roller is measured, the guide rod is displaced upward, and the iron core is also displaced upward in the differential coil. The output voltage varies with the displacement. When the displacement exceeds the center position, the differential transformer outputs a positive voltage. ② Oscillator: A high-frequency triode is used as a capacitive voltage divider oscillator with an oscillation frequency of 4KHz. This circuit feature avoids the difficulty of inductive oscillator winding. The intermediate transformer is used to couple the output, and then through the first-stage voltage amplification, the two pairs of Zener diodes are used to limit the clipping to form a rectangular wave with constant amplitude (2~3V), one way is for the primary excitation of the differential transformer and the other is for the phase-sensitive rectification comparison voltage. ③ AC amplifier: three-stage amplification circuit and transformer-coupled output. In order to keep the amplifier gain stable, 20dB negative feedback is introduced between the first and second stage, and the total gain is 75~80dB. ④ Phase-sensitive rectifier circuit: diode half-wave phase-sensitive rectification is used, the comparison voltage amplitude is high, and both diodes are turned on in the positive half cycle. The signal voltage is small, the positive voltage is output in the same phase with the comparison voltage, and the negative voltage is output in the opposite phase with the comparison voltage. ⑤ DC differential amplifier: The DC voltage output from the phase-sensitive rectifier circuit is further amplified and the polarity is converted. When inputting ±50mV, the differential output is 4~12V. 8.3 Discussion of Differential Transformer Application(1) The above example uses the two directions of the differential transformer and is determined for the special purpose of roller sorting. When measuring with a roller of nominal size, the differential transformer core is just adjusted to the center position, the positive tolerance roller produces a positive displacement, and the positive voltage is output; the negative tolerance roller produces a negative displacement and outputs a negative voltage. This makes full use of the linear range of the differential transformer. For different applications, especially for small-range, high-precision measurements, there is no need to distinguish the direction of the displacement. It is also possible to use only the displacement of the differential transformer in one direction, and the corresponding circuit can be simplified. (2) This product was a product of the 1970s, so a transistor discrete component circuit was used. Today's electronic technology and the component levels are no longer the same. AC amplifiers and DC amplifiers can be used with operational amplifiers, and performance is much better than discrete component circuits. The basic principles of the circuit and the various functional parts are still applicable and can be designed accordingly. (3) Nowadays, the application of single-chip microcomputers can completely replace the various logic circuits in the past. In the case of a single-chip microcomputer, the entire circuit design may vary greatly. For example, the oscillation source can be digitized (crystal oscillator frequency division may be directly generated by a single-chip microcomputer), and the measurement result is digitized (via A/D conversion), and a large number of analog comparators, triggers can be replaced by program judgment methods.  Furthermore, with the precise timing and synchronization function of the single-chip microcomputer, A/D conversion can be directly performed on the AC signal sampling, and the phase-sensitive rectifier circuit can be omitted. After the measurement results are digitized, data transmission can be used instead of analog transmission, thus precision will not be lost, interference will not exist and transmission distance will be long. Ⅸ FAQ1. Why does LVDT use high voltage?It is a type of electrical transformer used for measuring linear displacement.The linear variable differential transformer has three solenoidal coils placed end-to-end around a tube. The center coil is the primary, and the two outer coils are the top and bottom secondaries. A cylindrical ferromagnetic core, attached to the object whose position is to be measured, slides along the axis of the tube. An AC current drives the primary and causes a voltage to be induced in each secondary proportional to the length of the core linking to the secondary.Cutaway view of an LVDT. Current is driven through the primary coil at A, causing an induction current to be generated through the secondary coils at B. When the core is displaced toward the top, the voltage in the top secondary coil increases as the voltage in the bottom decreases. The resulting output voltage increases from zero. This voltage is in phase with the primary voltage. When the core moves in the other direction, the output voltage also increases from zero, but its phase is opposite to that of the primary. The phase of the output voltage determines the direction of the displacement (up or down) and amplitude indicates the amount of displacement.  2. What are the advantages of using an LVDT?• Very reliable: Long sensor lifespan due to near frictionless operation of most models.• Very high resolution: Because of the near-frictionless movement they provide virtually infinite resolution. Even the smallest changes can be detected.• Damage resistant: In some models, both ends of the tube are open, preventing sensor damage if the test article pushes the rod farther than expected (except for collision with the tube itself).• Null point stability: The zero or null point of the sensor is extremely repeatable due to the construction of the sensor itself.• Wide range of operating temperatures: There are LVDT models available that can withstand cryogenic temperatures (-200℃/ -328℉) as well as high temperatures (650℃/ 1200℉)• Low hysteresis/ high positional accuracy and repeatability• Absolute reading output device: As opposed to an incremental output device, the reading from an LVDT will be the same before and after its power is cycled (assuming that the object under test did not move).  3.What are the disadvantages of using an LVDT?• Limited measurement distance: Even the largest LVDTs are limited to less than 1m (~27'') measurement ranges.• Can be affected by magnetic fields (models with shielding are common as a result).• AC models require a precise AC excitation from an LVDT signal conditioner.• DC LVDT models have an inferior shock, vibration and temperature specifications compared to AC LVDT models. 4. How do I interface an LVDT output with PLC?The output is voltage so you will need an analog input card which can take in a voltage input and then inside the PLC you will scale what that voltage corresponds to. For eg 10 V could mean 10 mm or 10 degrees etc. If the output is current them you would need an analog IP card which accepts current. Most common current used is 4–20 mA. 5. What are the applications of the Bourdon tube and the LVDT method for pressure measurement?A bourdon tube is a curved, hollow, closed end tube which can be pressurized. The pressure will attempt to straighten out the tube as it is increased. The amount of movement is typically very small but can be mechanically amplified. The translation of the end of the tube can be a linear indication of the pressure applied to the other end.Pressure gauges have used this technique for over a century and a half to indicate pressure manually on a dial gauge with a linkage that moves a dial pointer.To make electronic readouts of pressure to remote dials or to computers, a linear movement to electrical voltage is needed. An LVDT satisfies this need. An LVDT is a variable transformer consisting of a movable magnetic core sliding inside a tube with a primary and secondary winding. As the core is displaced the coupling between windings is varied linearly. If a small AC voltage is applied to the primary then the amplitude of the secondary output can be measuered in amplitude to indicate proportional to the pressure.So this makes a hybrid sensor or transducer, pressure to displacement connected to a displacement to variable voltage resulting in a pressure to variable voltage device.Technically this is an older way of converting pressure to volts… and is subject to hysteresis or mechanical backlash. Most modern P-V transducers use strain gauge bridge followed by an instrumentation amplifier to have fewer moving parts and less hysteresis. 6. Discuss various applications where LVDT’s can be used?They can be used in any application where a highly accurate measurement of linear displacement or position is needed. This includes precision gaging systems for measurement and metrology, feedback transducers for precision servomechanisms, torque, force and moment transducers, materials testing equipment (tensile testers, rheometers, fatigue testers, etc.). 7.What is the accuracy of a LVDT and an inductance transducer in a displacement measurement?Accuracy for both devices depends on the way they are designed, made and used, and the materials from which they are made. As well as calibration.However, neither on their own give “readings”. They need conditioning and interface circuitry. (I do recognise that the “inductance transducer” is a two-word item, and that the second word - transducer - implys that at least some form of signal conditioning exists therein.)That cicuitry is at least as important as the device itself.To give typical values for accuracy, is difficult without more specifics, though it is usual to be able to achieve several significant figures of accuracy out of each. 8. What is LVDT in measurement?A Linear Variable Differential Transducer is a sensor based on the idea of transformers. As its name shows it's a Linear sensor used in measuring displacements.  It has an iron core that moves up and down in the gap separating the primary and secondary coils. So the coils are not physically connected. The secondary coils are connected in opposition such that the output voltage is the difference between the voltages induced in the first and second secondary coils. The components whose Displacement is required to be measured should be connected to the core, so the input to the sensor is the displacement، the output would be the differential voltage output and after some manipulation using the sensitivity and sensor resolution, the displacement can be obtained. 9. How does a DC LVDT work?An oscillator/demodulator circuit built into the displacement transducer supplies the excitation and converts the return signal to a dc voltage. ... As the transducer contains internal signal conditioning electronics, there is no need for external signal conditioning. 10. Is LVDT an active transducer?The active transducer is also called a self-generating type transducer. ... Example of an active transducer is the bourdon tube. An example of a passive transducer is LVDT (linear variable differential transformer). It generates electric current or voltage directly in response to environmental stimulation.

CatalogⅠ IntroductionⅡ What is an infrared sensor?Ⅲ How does the infrared sensor work?Ⅳ The basic law of infrared radiationⅤ The working principle of the infrared sensorⅥ Types of infrared sensors  6.1 Thermal sensor  6.2 Photon sensorⅦ Application and Prospect of the infrared sensorⅧ SummaryⅨ FAQⅠ IntroductionAny object in the universe can produce infrared radiation as long as its temperature exceeds zero. In fact, like visible light, its radiation can be refracted and reflected, which leads to infrared technology. Infrared detector is widely used in military and civil fields because of its unique advantages. In the military, infrared detection is used for guidance, fire control tracking, alert, target detection, weapon thermal sight, ship navigation, etc.; in the civil field, it is widely used in industrial equipment monitoring, safety monitoring, disaster relief, remote sensing, traffic management, medical diagnosis technology, etc.With the development of science and technology, the proportion of automatic control and automatic detection in people's daily life and industrial control is more and more heavy, which makes people's life more and more comfortable and the efficiency of industrial production higher and higher. The sensor is an important component of the automatic control, and an important component of the information acquisition system.  Through the sensor, the feeling or response is measured and converted into a signal suitable for transmission or detection (generally electrical signal), and then the computer or circuit equipment is used to process the signal from the sensor to achieve the function of automatic control. Because the response time of the sensor is generally short, the real-time control of industrial production can be carried out through the computer system. The infrared sensor is a common type of sensor.  Because an infrared sensor is a kind of sensor to detect infrared radiation, and any object in nature will radiate infrared energy as long as its stability is higher than absolute zero, so infrared sensor is called a very practical type of sensor. Many practical sensor modules can be designed by using infrared sensors, such as infrared temperature measurement Instruments, infrared imagers, infrared human detection alarms, automatic door control systems, etc.Ⅱ What is an infrared sensor?Infrared sensor is a sensor that uses the physical properties of infrared to measure. Infrared light, also known as infrared light, has the properties of reflection, refraction, scattering, interference, absorption, etc. It is a kind of invisible light, its spectrum is located outside red in visible light, so it is called infrared. In engineering, the position (band) of infrared rays in the electromagnetic spectrum is divided into four bands: near infrared band, mid infrared band, far infrared  band and extremely far infrared band. Any substance can radiate infrared ray, as long as it has a certain temperature (higher than absolute zero).Ⅲ How does the infrared sensor work?First of all, let's learn about infrared light. Infrared light is a part of the solar spectrum. The biggest characteristic of infrared light is its photothermal effect and radiant heat. It is the largest photothermal effect area in the spectrum. An invisible light, like all electromagnetic waves, having the properties of reflection, refraction, scattering, interference, absorption, etc. The propagation speed of infrared light in a vacuum is 300000 km / s. The transmission of infrared light in the medium will produce attenuation, and the transmission attenuation in the metal is very large, but the infrared radiation can pass through most semiconductors and some plastics, and most liquids absorb the infrared radiation very much.Different gases have different absorption levels, and the atmosphere has different absorption bands for different wavelengths of infrared light. The results show that the infrared light with the wavelength of 1-5 μ m and 8-14 μ m has a relatively large "transparency". That is to say, these wavelengths of infrared light can penetrate the atmosphere well. Any object in nature, as long as its temperature is above absolute zero, can produce infrared radiation. The photothermal effect of infrared light is different for different objects, and the intensity of heat energy is also different.  For example, blackbody (an object that can fully absorb the infrared radiation projected on its surface), mirror body(an object that can fully reflect the infrared radiation), transparent body(an object that can fully penetrate the infrared radiation) and gray body (an object that can partially reflect or absorb the infrared radiation) will produce different photothermal effects. Strictly speaking, there are no blackbody, mirror body and transparent body in nature, and most of the objects belong to gray body. These characteristics are the important theoretical basis for the application of infrared radiation technology in military and scientific research projects such as satellite remote sensing and infrared tracking. The physical essence of infrared radiation is thermal radiation. The higher the temperature of an object, the more infrared it radiates, the stronger the energy of the infrared radiation. It is found that the thermal effect of various monochromatic light in the solar spectrum increases gradually from violet light to red light, and the largest thermal effect occurs in the frequency range of infrared radiation, so people call infrared radiation as thermal radiation or thermal ray.Ⅳ The basic law of infrared radiation① Kirchhoff's Law: at a certain temperature, the ratio of the radiation flux W per unit area of the ground object to the absorption rate is a constant for any object, and is equal to the radiation flux w of a blackbody of the same area at that temperature. At a given temperature, the emissivity of the object = the absorptivity (the same band); the higher the absorptivity, the higher the emissivity. The thermal radiation intensity of the ground object is directly proportional to the fourth power of the temperature, so the small temperature difference of the ground object will cause the obvious change of the infrared radiation energy. This feature constitutes the theoretical basis of infrared remote sensing.② Boltzmann's Law: that is, the total radiation flux of blackbody increases rapidly with the increase of temperature, which is proportional to the fourth power of temperature. Therefore, a small change in temperature will cause a great change in radiation flux density. It is the theoretical basis of measuring temperature with an infrared device. ③ Wien displacement law: with the increase of temperature, the peak wavelength corresponding to the maximum radiation value moves to the short wave direction.Ⅴ The working principle of the infrared sensorThe working principle of the infrared sensor is not complicated. The entities of each part of a typical sensor system are as follows:• Target to be tested: the infrared system can be set according to the infrared radiation characteristics of the target to be tested.• Atmospheric attenuation: when the infrared radiation of the target to be measured passes through the earth's atmosphere, the infrared radiation from the infrared source will be attenuated due to the scattering and absorption of gas molecules, various gases and various colloidal particles.• Optical receiver: it receives part of the infrared radiation of the target and transmits it to the infrared sensor. Equivalent to radar antenna, usually objective lens.• Radiation modulator: it can modulate the changed radiation light from the target to be tested, provide the target orientation information, and filter out large-area interference signals. Also known as modulation disk and chopper, it has a variety of structures.• Infrared detector: This is the core of the infrared system. It is a sensor that uses the physical effect of the interaction between infrared radiation and matter to detect infrared radiation. In most cases, it uses the electrical effect of the interaction. These detectors can be divided into two types: photon detector and heat-sensitive detector.• Detector Cooler: because some detectors must work at low temperatures, the corresponding system must have refrigeration equipment. After refrigeration, the equipment can shorten the response time and improve the detection sensitivity.• Signal processing system: amplify and filter the detected signals, and extract information from these signals. Then, this kind of information is transformed into the required format, and finally transmitted to the control equipment or display.• Display device: This is the terminal device of infrared device. Commonly used displays include oscilloscopes, picture tubes, infrared sensitive materials, indicating instruments and recorders.According to the above process, the infrared system can complete the corresponding physical quantity measurement. The core of infrared system is infrared detector. According to the different detection mechanism, it can be divided into two categories: thermal detector and photon detector. The thermal detector absorbs all the radiant energy of all kinds of incident wavelengths. It is an infrared sensor with no choice for infrared light wave. The common photon effects of photon detectors are external photoelectric effect, internal photoelectric effect (photovoltaic effect, photoconductive effect) and photoelectromagnetic effect. The thermal detector uses the radiation heat effect to make the temperature rise after the detector receives the radiation energy, and then the temperature-dependent performance of the detector changes.  Radiation can be detected by detecting a change in one of the properties. In most cases, radiation is detected by thermoelectric changes. When the element receives radiation and causes the physical change of non electric quantity, the corresponding electric quantity change can be measured after appropriate transformation. The response time of thermal detector to infrared radiation is much longer than that of photodetector. The response time of the former is generally more than MS, while that of the latter is only ns. Thermal detectors do not need to be cooled, most photon detectors need to be cooled.Ⅵ Types of infrared sensorsCommon infrared sensors can be divided into thermal sensors and photon sensors.6.1 Thermal sensorThe thermal sensor uses the incident infrared radiation to change the temperature of the sensor, and then make the relevant physical parameters change accordingly. The infrared radiation absorbed by the infrared sensor is determined by measuring the changes of the relevant physical parameters. The main advantage of the thermal detector is that it has a wide band, can work at room temperature and is easy to use. However, the thermal sensor has a long response time and low sensitivity, which is generally used in low frequency modulation.The main types of thermal sensors are thermal sensor type, thermocouple type, gaolai pneumatic type and heat release electric type. ① Thermistor sensorThe thermistor is made of manganese, nickel and cobalt oxides. The thermistor is usually made into thin sheet. When the infrared radiation irradiates the thermistor, its temperature increases and the resistance decreases. By measuring the change of the thermistor value, we can know the intensity of the incident infrared radiation, thus we can judge the temperature of the object generating the infrared radiation.② Thermocouple sensorThermocouples are made of two materials with a great difference in thermal power. When infrared radiation reaches the contact of the closed circuit composed of these two metal materials, the contact temperature increases. The other contact which is not irradiated by infrared radiation is at a lower temperature, at this time, the temperature difference current will be generated in the closed circuit. At the same time, thermoelectric potential is generated in the loop, and the magnitude of thermoelectric potential reflects the strength of infrared radiation absorbed by the contact. The infrared sensor made of thermoelectric potential is called thermocouple infrared sensor. Because of its large time constant, long corresponding time and poor dynamic characteristics, the modulation frequency should be limited below 10Hz.③ Lai pneumatic sensorAfter absorbing the infrared radiation, the temperature and volume of the gas are increased to reflect the intensity of the infrared radiation. It has an air chamber connected to a flexible sheet by a small pipe.  One side of the back pipe of the sheet is a reflector. The front of the gas chamber is attached with an absorption mode, which is a thin film with low heat capacity. The infrared radiation is incident on the absorption mode through the window, and the absorption mode transmits the absorbed heat energy to the gas, which makes the gas temperature and pressure increase, so that the flexible mirror moves.  On the other side of the chamber, a beam of visible light is focused on the flexible mirror through the grating light bar, and the grating image reflected by the flexible mirror is projected onto the photoelectric cell through the grating light bar. When the flexible mirror moves due to the change of pressure, the relative displacement between the grating image and the grating light bar will change the amount of light falling on the photocell, and the output signal of the photocell will also change, which reflects the intensity of the in-out infrared radiation.  This sensor is characterized by high sensitivity and stable performance. But the response time is long, the structure is complex and the intensity is poor, so it is only suitable for laboratory use. ④ Pyroelectric sensorPyroelectric sensor is a kind of thermal crystal or ferroelectric with polarization phenomenon. The polarization intensity (charge per unit area) of ferroelectrics is related to temperature. When infrared radiation irradiates the surface of the polarized ferroelectric sheet, the temperature of the sheet increases, the polarization intensity decreases, and the surface charge decreases, which is equivalent to releasing part of the charge, so it is called pyroelectric sensor.  If the load resistor is connected to a ferroelectric sheet, an electrical signal output is generated on the load resistor. The size of the output signal depends on the speed of the temperature change of the chip, which reflects the intensity of the incident infrared radiation. It can be seen that the voltage response rate of the pyroelectric infrared sensor is directly proportional to the change rate of incident radiation. When the constant infrared radiation irradiates on the pyroelectric sensor, the sensor has no electrical signal output.  Only when the temperature of ferroelectrics is in the process of change can the electrical signal be output. Therefore, it is necessary to modulate the infrared radiation (or chopping light) so that the constant radiation becomes the alternating radiation, which constantly causes the temperature change of the sensor, so as to generate pyroelectric and output the alternating signal.6.2 Photon sensorThe photon sensor uses some semiconductor materials to produce photon effect under the illumination of incident light, which changes the electrical properties of materials. By measuring the change of electrical properties, we can know the intensity of infrared radiation. The infrared sensors made by photon effect are called photon sensors. The main characteristics of photon sensor are high sensitivity, fast response speed and high response frequency, but generally it must work at low temperature and the detection band is narrow. According to the working principle of photon sensor, it can be divided into internal photoelectric sensor and external photoelectric sensor. The latter is divided into photoconductive sensor, photovoltaic sensor and magnetoelectric sensor. ① External photoelectric sensorWhen the light radiates on the surface of some materials, if the photon energy of the incident light is large enough, the electrons of the materials can escape from the surface. This phenomenon is called external photoelectric effect or photoelectron emission effect. Photodiode, photomultiplier tube and so on belong to this type of electronic sensor. Its response speed is relatively fast, generally only a few nanoseconds. However, electron escape requires a large amount of photon energy, which is only suitable for near-infrared radiation or visible light. ② Photoconductive sensorWhen infrared radiation irradiates on the surface of some semiconductor materials, some electrons and holes in the semiconductor materials can change from the original non-conductive bound state to the conductive free state, which increases the conductivity of the semiconductor. This phenomenon is called the photoconductivity phenomenon. The sensors made of photoconductive phenomena are called photoconductive sensors.  For example, lead sulfide, lead selenide, indium antimonide, mercury telluride and other materials can be used to make photoconductive sensors. When using photoconductive sensor, we need to cool and add a certain bias voltage, otherwise, the response rate will be reduced, the noise will be large, the response band will be narrow, and the infrared sensor will be damaged.③ Photovoltaic sensorWhen the infrared radiation irradiates on the PN junction of some semiconductor materials, the free electrons move to the N-region under the action of the electric field in the junction. If the PN junction is open, an additional potential will be generated at both ends of the PN junction, which is called the photogenerated electromotive force.  The sensors or PN junction sensors based on this effect are usually made of materials such as indium arsenide, indium antimonide, mercury telluride, lead-tin telluride, etc. ④ Magnetoelectric sensorWhen the infrared radiation irradiates on the surface of some semiconductor materials, some electrons and holes in the semiconductor materials will diffuse to the interior. If the diffusion is affected by a strong magnetic field, the electrons and holes will each deviate to one side, resulting in an open circuit voltage. This phenomenon is called the optical magnetoelectric effect. The infrared sensor made of this effect is called magnetoelectric sensor. The response band is about 7 μ m, the time constant is small, the response speed is fast, there is no bias, the internal resistance is very low, the noise is small, and it has good stability and reliability. However, its sensitivity is low and it is difficult to make low noise preamplifier, which affects its use.Ⅶ Application and Prospect of the infrared sensor (1) The application of infrared sensor is mainly reflected in the following aspects:    1. Infrared radiometer: used for radiation and spectral radiation measurement.    2. Search and tracking system: used to search and track the infrared target, determine its spatial position and track its motion.    3. Thermal imaging system: it can form the infrared radiation distribution image of the whole target.    4. Infrared ranging system: to measure the distance between objects. (it uses the non-proliferation principle of infrared propagation, because the refractive index of infrared is very small when it passes through other substances, so infrared will be considered in long-distance distance distance rangefinders.)    5. Communication system: infrared communication as a way of wireless communication.    6. Hybrid system: refers to two or more combinations of the above systems.Infrared sensor applications can be used for non-contact temperature measurement, gas composition analysis, nondestructive testing, thermal image detection, infrared remote sensing and military target reconnaissance, search, tracking and communication. With the development of modern science and technology, the application prospect of infrared sensor will be more broad. In the future, the performance and sensitivity of infrared sensor will be improved greatly.  (2) Development trend    1. Intellectualization: at present, the infrared sensor is mainly used in combination with peripheral equipment. The built-in microprocessor of the intelligent sensor can realize the two-way communication between the sensor and the control unit. It has the advantages of miniaturization, digital communication, simple maintenance, etc., and it can work independently as a module.     2. Miniaturization: an inevitable trend of sensor miniaturization. Now in application, because of the volume problem of infrared sensor, its use degree is far worse than that of thermoelectric corner. Therefore, whether the infrared sensor is miniaturized and portable or not can't be ignored.     3. High sensitivity and high performance: in medicine, the infrared sensor has been widely used for the measurement of human body temperature, but it can not replace the existing temperature measurement method due to its low accuracy. Therefore, the high sensitivity and high performance of infrared sensor is the inevitable trend of its future development.Ⅷ SummaryAlthough there are many deficiencies in the current infrared sensor, the infrared sensor has played a huge role in modern production practice. With the improvement of detection equipment and other parts of the technology, the infrared sensor can have more performance and better sensitivity and will have a broader application range. Ⅸ FAQ1. What is the working principle of the IR sensor?Active infrared sensors both emit and detect infrared radiation. Active IR sensors have two parts: a light-emitting diode (LED) and a receiver. When an object comes close to the sensor, the infrared light from the LED reflects off of the object and is detected by the receiver. 2. Why is an infrared sensor important?An infrared sensor is an electronic instrument that is used to sense certain characteristics of its surroundings. It does this by either emitting or detecting infrared radiation. Infrared sensors are also capable of measuring the heat being emitted by an object and detecting motion. 3. What is an IR sensor for kids?Light waves longer than red light waves are called infrared light (IR). We cannot see either UV and IR light without special equipment or photography. In the case of infrared sensors, an infrared light source, which is typically an IR LED, is used to transmit light to a receiving infrared sensor. 4. Can IR sensors detect humans?The Passive Infrared (PIR) sensor is used to detect the presence of humans. But this detects the human only if they are in motion. Every human radiates the infrared energy of a specific wavelength range. The absorbed incident radiation changes the temperature of a material. 5. Where are IR sensors used?A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. PIR sensors are commonly used in security alarms and automatic lighting applications. 6. How do you bypass an infrared sensor?Most motion detectors, even newer ones, use infrared to detect significant changes in the surrounding room's temperature, Porter said. Normally, walking around in a room would set off these sensors, but using something as simple as a piece of styrofoam to shield your body can trick them, he said. 7. What is the difference between an IR sensor and an ultrasonic sensor?The biggest difference between IR sensors vs. ultrasonic sensors is the way in which the sensor works. Ultrasonic sensors use sound waves (echolocation) to measure how far away you are from an object. On the other hand, IR sensors use Infrared light to determine whether or not an object is present. 8. What is the range of the IR sensor?An infrared sensor (IR sensor) is a radiation-sensitive optoelectronic component with spectral sensitivity in the infrared wavelength range 780 nm ...50 µm. IR sensors are now widely used in motion detectors, which are used in building services to switch on lamps or in alarm systems to detect unwelcome guests. 9. Can an IR sensor detect temperature?Infrared temperature sensors sense electromagnetic waves in the 700 nm to 14,000 nm range. ... Because the emitted infrared energy of any object is proportional to its temperature, the electrical signal provides an accurate reading of the temperature of the object that it is pointed at. 10. How do IR sensors detect obstacles?An infrared sensor emits and/or detects infrared radiation to sense its surroundings. ... The basic concept of an Infrared Sensor which is used as an Obstacle detector is to transmit an infrared signal, this infrared signal bounces from the surface of an object and the signal are received at the infrared receiver.