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A high-output-power balanced power amplifier is designed with power-combining architecture for satellite communication terminals. The power-combining architecture introduces a ±45° phase shift in the output matching network of two amplifiers, which makes the balanced power amplifier more tolerant to load mismatch and less sensitive to load variation. This balanced power amplifier is implemented with InGaP/GaAs HBT process. Under the band of 1.5 GHz to 1.7 GHz and the supply voltage of 5 V, the measured results show that 32 dB of the gain, 38 dBm of the saturated output power and 43% of power added efficiency (PAE) are achieved, and a good radio frequency performance can be maintained under load mismatch conditions. Power Amplifier ( PA ) Basics and fundamental tutorial on radio frequency Catalog Ⅰ Introduction of Power Amplifier 1.1 Background of power amplifier 1.2 Application of power amplifier in power combination scheme 1.3 High power balanced power amplifier Ⅱ Design and Analysis of balanced Power Amplifier 2.1 Design of Integral circuit 2.2 Circuit Analysis Ⅲ Test result Ⅳ Conclusion FAQ Ⅰ Introduction of power amplifier 1.1 Background of power amplifier In recent years, with the development of economy, satellite communication and navigation systems are widely used in electronics and automobile industry,and the demand for power amplifiers of handheld terminal transmitters is increasing.These power amplifiers require greater power output and better stability to meet the performance requirements of satellite communications and navigation systems. Therefore, it is of great significance to study the practical and reliable high power integrated power amplifier used in the handheld terminal of satellite communication and navigation system. The traditional single-terminal multi-stage integrated power amplifier is not only low in output power, due to the influence of its own semiconductor physical characteristics and the limitations of processing technology, heat dissipation, impedance matching, etc, but the output power will also decrease rapidly with the increase of frequency. In order to improve the output power, the power combination technology is a practical and easy method to implement. At the same time, the balanced power amplifier is widely used in the power synthesis scheme because of its insensitive load and wider bandwidth than the single-ended power amplifier. 1.2 Application of power amplifier in power combination scheme In reference, a high linearity and high efficiency power amplifier is realized by balanced synthesis method. The power amplifier has the advantages of flat gain characteristics and more stability than the corresponding single-ended amplifier in a wide band. However, the introduction of orthogonal 3dB couplers at the input and output ends makes the power amplifier require more discrete devices, which is not conducive to miniaturization and integration. In reference, a novel balanced synthesis architecture was used to design a load insensitive power amplifier.This kind of power amplifier adds ±45 °phase shift network to the upper input and lower output terminals, and finally combines the two power channels through the Wilkinson synthesizer at the output end. This design not only achieves high efficiency and linearity, but also has good stability when the load changes. It is widely used in 3G WCDMA mobile phone terminals. However, the introduction of Wilkinson synthesizer also brings many disadvantages, such as large insertion loss, increasing integration cost and complexity. In reference, on the basis of reference, the ±45°phase shift network in the output end of the power amplifier is improved and optimized, the Wilkinson synthesizer is removed either, which makes the power amplifier insensitive to the load change while achieving high efficiency and high linearity.This design reduces the integrated devices, reduces the cost, and is widely used in modern 3G smart phone terminals. 1.3 High power balanced power amplifier Based on the comprehensive consideration of output power and stability, a high power balanced power amplifier based on InGaP/GaAs HBT process, operating in the 1.5-1.7 GHz band, is designed in this article. The test results show that the balanced power amplifier has high output power and power addition efficiency (PAE), and the circuit can still maintain good RF performance when the load mismatches. Ⅱ Design and analysis of balanced power amplifier 2.1 Design of Integral circuit Due to the superior linearity and high efficiency of HBT process in RF IC design, a balanced power amplifier working in 1.5-1.7 GHz band is designed by using InGaP/GaAs HBT process in this article. The overall circuit structure is shown in figure 1. The balanced power amplifier circuit includes the same upper and lower branch amplifiers, and the input and output matching circuits of ±45°phase-shifting networks. In order to obtain a higher gain, the upper and lower branches are designed using a three-stage power amplifier structure, in which the first stage works in a class A to obtain a high linearity; in order to take into account the linearity and efficiency of the overall power amplifier, the second and third stages work in Class AB. Figure 1. A balanced power amplifier circuit In order to achieve a good compromise between efficiency and linearity, the biasing circuit adopts self-adaptive linearizing bias.By adding one inductor and one capacitance to the input matching circuit of the upper and lower branches, the balanced power amplifier generates ±45°phase shift to the input signal, thus realizing that the upper and lower channels of the amplifier work in an orthogonal state. A LC resonant network with a resonant frequency of 2Ω0 is added to the output matching, where Ω0 is the fundamental frequency, which is equivalent to getting a load of second harmonic short circuit at the same time, thus realizing the suppression of the second harmonic. The structure is similar to that of F power amplifier, and is beneficial to obtain higher efficiency. The main characteristic of the circuit in this article is that the output matching circuit of the upper and lower branches added a ±45°phase shift network, the upper branch adds a -45°phase shift network with a low pass filter structure, and the lower branch adds a +45°phase shift network with a high pass filter structure. The balanced power amplifier designed by this synthetic structure has the advantages of small space usage, simple structure and easy implementation. At the same time, it can make the balanced power amplifier more tolerant to load mismatch and insensitive to the change of load. 2.2 Circuit Analysis When the balanced power amplifier is in operation, the input signal is coupled to the A node through the blocking capacitor, and two signals are separated from the A node into the upper and lower branches respectively, because the three-stage amplifier in the upper and lower branches is exactly the same, they sharing an equal input impedance, so the power of the two signals separated at the A node is equal. The separated signals are transmitted to the input end of the amplifier through the opposite 45°phase change of the upper and lower branches respectively, and then the orthogonal signals are amplified by the three-stage amplifier of the upper and lower branches. The orthogonal signal of the upper and lower branches undergoes an opposite phase shift of 45° in the output matching network, so the same signal with the same phase and the same amplitude is realized at point B, and the output power of point B is the sum of those of the two amplifiers, finally the balanced power amplifier can obtain higher output power. The balanced power amplifier is equivalent to the three-port network shown in figure 2. Because the upper and lower branch of amplifiers are exactly the same,it can be considered that the amplifiers of the upper and lower branches have the same output reflection coefficient ΓPA. After passing through ±45°phase shift network, we can obtain ΓPAе −j2ΔΦ and ΓPAе +j2ΔΦ respectively. Therefore, the equivalent output impedance of the upper and lower branches viewed from the ab surface to the left in figure 2 is respectively as follows: The equivalent output impedance ZL of the network viewed from the terminal to the left can be obtained in parallel by ZL1 and ZL2: The output reflection coefficient of node B is: By substituting formula (1)-(3) into equation (4) and simplifying, the output reflection coefficient of the balanced power amplifier is as follows: When ΔΦ=45°, you have: It is shown that the output reflection coefficient and VSWR of the balanced power amplifier are twice as much as that of the single branch power amplifier. Therefore, when the load mismatch occurs, the load mismatch tolerance of the balanced power amplifier is higher than that of the single-branch power amplifier after the ±45°phase shift output matching network is introduced. Figure 2. Circuit equivalent diagram In order to analyze the performance of the balanced power amplifier in the case of load mismatch, the equivalent circuit of figure 2 is simulated and analyzed. When the load mismatch (such as VSWR=3:1), the load impedance (normalized) of the upper and lower branch amplifiers varies with the phase ψ of the reflection coefficient Γ, as shown in figure 3. By comparing the load impedance of the upper and lower branches, it can be seen that they have a phase difference of 180°. Because of the change of the load impedance of the upper and lower branches, the corresponding current is changed, and the phase difference of 180°occurs between the two. The collector of the two third-stage amplifiers of the balanced power amplifier is single power supply, so the current of the upper and lower branches compensates each other, resulting in little change in the total current, as shown in Figure 4. Therefore, when the load mismatch of the balanced power amplifier occurs, the change of working current is relatively small, that is, not sensitive to the change of load. The load insensitive effect of using this balancing architecture is similar to that of classical balanced power amplifier which is realized by using orthogonal 3 dB coupler. Figure 3. Changes in the load of the structure (normalized) when VSWR=3:1 In the case of terminal mismatch (VSWR=3:1), the single end circuit architecture and the present balanced architecture are compared as shown in Fig. 5 with the same output power of 38 dBm. It can be seen from figure 5 that the output power of the single-ended circuit architecture fluctuates greatly with of the phase ψ of the reflection coefficient Γ, while the output power of the balanced architecture in this article is relatively flat. At the same time, compared with the circuit architecture without phase shift, the in-phase circuit architecture has more advantages than the single-ended circuit architecture, but the output power of the balanced architecture is the flattest and can work stably. Figure 4. Changes of current of the structure (normalized) when VSWR=3:1 Figure 5. Comparison with the output power (normalized) changes in three kinds of circuits when VSWR=3:1 Ⅲ Test result In this post, the balanced power amplifier is fabricated by InGaP/GaAs HBT technology. The three-stage amplifier and bias circuit with upper and lower branches are realized in the chip with an DIE area of 0.9 mm×0.8 mm. The choke inductor, input matching and output matching circuit are realized out of the chip. Considering the heat dissipation of the power amplifier, the whole thing is integrated on the Fr4 substrate with an area of 8 mm×8 mm. Figure 6 is the physical diagram of the circuit.The working voltage of the balanced power amplifier is 5 V and the total static current is about 310 mA. Using Agilent's network analyzer E5071C to measure the small signal S parameters S21, S11, S22 of the balanced power amplifier, as shown in figure 7: S21 > 31 dB (in the band of 1.5 GHz-1.7 GHz with a variation of less than 1 dB) S11 < -12 dB S22 < -10 dB The test results show that the design has good small signal performance. Using Agilent's signal generator N5182A and spectrometer N9030A to build the test platform, inputting continuous wave (CW) and the performance of the balanced power amplifier is measured at 1.5,1.616 and 1.7 GHz, as shown in figure 8. It can be seen from the diagram that the gain of the balanced power amplifier in the frequency band is about 32 dB, the in-band gain flatness is ±0.3 dB, the saturation power is more than 38 dBm/6.3 WN, and the power additional efficiency is greater than 43 dB. At the same time, according to the gain curve of each frequency point, the balanced power amplifier has good AM-AM characteristic and 1dB compression point is about 37 dBm. The third order intermodulation distortion (IMD3) and the fifth order intermodulation distortion (IMD5) of the balanced power amplifier are measured by using a two-tone signal with a deviation of 2 MHz, as shown in figure 9. The results show that the balanced power amplifier has good linearity. In general, the balanced power amplifier not only has high gain, high output power and high efficiency, but also has good linearity. Figure 6. Chip physical diagram Figure 7. S parameter test results Figure 8. Test performance in frequency band when CW signal is input In order to verify the tolerance of the balanced power amplifier to the load mismatch and the load insensitivity, and the balanced power amplifier can still work properly when VSWR=20:1, a microwave manual tuner is connected to the output of the power amplifier. And when the working frequency is 1.616 GHz, the input power Pin=10 dBm and voltage standing-wave ratio VSWR=3:1, the output power of the balanced power amplifier changes with the reflection coefficient phase, as shown in Figure 10. The figure shows that the output power is about 35.7 dBm, with a range of ±0.7 dBm. Therefore, the performance of the balanced power amplifier is stable when the load is mismatched to a certain extent. Figure 9. Test performance of IMD3 and IMD5 Figure 10. Changes of output power when VSWR=3:1 Ⅳ Conclusion In this post, a high power balanced power amplifier is designed by using the balance architecture, the chip area is 8 mm×8 mm by using InGaP/GaAs HBT process and the total static current is about 310 mA at a operating voltage of 5V. When the CW signal is input, the gain can be up to 32 dBm in the band of 1.5-1.7 GHz, the saturation output power psat is 38 dBm, and the additional power efficiency is 43%. Beyond that, it can still work stably when the load mismatches. This balanced power amplifier is practical, reliable and safe, and can be used in handheld terminal of the satellite communication and navigation system. FAQ 1. What is a power amplifier used for? The function of a power amplifier is to raise the power level of input signal. It is required to deliver a large amount of power and has to handle large current. The base of transistor is made thicken to handle large currents. 2. How does a power amplifier work? The power amplifier works on the basic principle of converting the DC power drawn from the power supply into an AC voltage signal delivered to the load. Although the amplification is high the efficiency of the conversion from the DC power supply input to the AC voltage signal output is usually poor. 3. Does a power amp make a difference? A better amp will make your speakers play louder and sound better, but it won't make bad speakers sound like good speakers. Many speakers have a "maximum wattage rating" on the back. ... High-end amplifier companies make amps with more than 1,000 watts, and you could plug in a $50 speaker into it with no problem. 4. What is power amplifier circuit? A power amplifier circuit is used to drive the loads like speakers with minimum output impedance. ... In this mode the output is an inverted amplified signal which is at low power. Two Darlington power transistors are arranged in a class AB configuration to amplify the power level of this signal. 5. How do you make a power amp circuit? Amplifier power gain and design. As power is the voltage multiplied by the current in a circuit, the power gain can simply be expressed as the product of the two. It is also possible to use the voltage and current levels to provide gain expressed in dB, but any changes in impedance must be accounted for. 6. What is balanced amplifier? A balanced amplifier has two amplifying devices that are run in quadrature. That is, they are operating 90 degrees apart in transmission phase. ... Balanced amplifiers may more immune to load pull effects than in-phase power combining schemes, because the two reflection coefficients are seen 180 degrees out of phase. 7. What is the difference between amplifier and power amplifier? The crucial difference between a voltage amplifier and a power amplifier is that a voltage amplifier increases the voltage level of the applied input signal. 8. Why do we need power amplifier? The function of a power amplifier is to raise the power level of input signal. It is required to deliver a large amount of power and has to handle large current. The base of transistor is made thicken to handle large currents. 9. What power amplifier do I need? Generally you should pick an amplifier that can deliver power equal to twice the speaker's program/continuous power rating. This means that a speaker with a “nominal impedance” of 8 ohms and a program rating of 350 watts will require an amplifier that can produce 700 watts into an 8 ohm load. 10. Does a power amp improve sound quality? No, amplifiers don't improve sound quality. They just increase the signals to required levels. However if amplifiers have equaliser or other signal processing facility, they can make it sound different and possibly more suitable for listening pleasure. But again that is the work of signal processing part of amplifier.
kynix On 2018-04-10
Warm hints: The word in this article is about 5400 words and reading time is about 25 minutes This article is equal to a comprehensive course about automobile sensors which including the basic introduction of automobile sensors, their types, applications, functions, and market analysis, etc. Electronic technology has become the leading factor in the direction of the development of a new generation of automobiles, and sensors are the core components of electronic technology. More and more modern cars have used sensors more and more, in order to improve the economic, dynamic and emission performance of automobile engines, improve the braking performance, steering performance and safety performance of the vehicle. The key to achieve these goals lies in the electronic and intelligent vehicle, the prerequisite is the timely acquisition of all kinds of information, which is bound to require a large number of sensors in the car. Catalogs I. An Overview of Automobile Sensors II. The Development History of Automobile Sensors III. Types of Automobile Sensors and Their Functions IV. Sensors Used in Automobile Engines and Their Functions 4.1 Automobile Temperature Sensor 4.2 Automobile Pressure Sensor 4.3 Air Flow Sensor 4.4 Fuel Flow Sensor 4.5 Engine Speed Sensor 4.6 Gas Concentration Sensor-oxygen Sensor V. Application of Vehicle Sensor in Vehicle Chassis Electronic Control System VI. Sensor Application in Automobile Safety System VII. Other Major Automotive Sensors VIII. Automotive Sensors Market Size--Its Market Trend FAQ I. An Overview of Automobile Sensors The automobile sensor is the input device of the automobile computer system. It takes all kinds of working condition information in the car, such as speed, temperature of various medium, engine operation condition and so on, and convert it into the device or device that can be input signal according to certain law. Simply speaking, the sensor transfers the non electric quantity to the electrical signal to transmit to the ECU, so that the car is in the best working state. An Overview of Automobile Sensors In modern automotive electronic control, sensors are widely used in various systems of engine, chassis, and body. Automobile sensors are responsible for the acquisition and transmission of information in these systems. The information collected by the sensors is processed by the computer (electronic control unit), and the instructions sent to the actuator are formed to complete the electronic control. The sensor is a very important device in the electronic control and self-diagnosis system. It can identify the changes in the outside world and the changes of the system itself in time and then control the work of the system itself according to the information of the change. Each system control process relies on sensors to feedback information and achieves automatic control. Automotive sensors usually consist of three parts: sensing element, converting element, and measuring circuit. (1)the sensitive element is the part that can be measured directly (or response), and is about to be converted into a non electric or other quantity that is determined to be determined by the sensing element of the sensor. (2)the conversion element converts the above non electric quantity into electrical parameters. (3)The function of the measurement circuit is to convert the electrical parameters input by the conversion element to the measurable quantity of voltage, current, or frequency, in order to display, record, control and handle the parts. Measurement circuit The sensor is at the interface between the research object and the test system, namely the first of detection and control. The sensor is a window to perceive, obtain and detect information. All the information obtained in the process of scientific research and automated production must be obtained by the sensor and converted into an easy transmission and processing electrical signal. Its role and status are particularly important. The following figure is the list of correspondence between the human body and machine, which helps us further understand its function. In modern automotive electronic control, sensors are widely used in various systems of engine, chassis, and body. The vehicle sensors are responsible for the acquisition and transmission of information in these systems. The computer (electronic control unit ECU) sends out instructions to the actuator after the signal is processed in a hurry, and the electronic control is implemented. The sensor is a very important device in the electronic control and self-diagnosis system. It can identify the changes in the outside world and the changes of the system itself in time and then control the work of the system according to the information of the change. Each system control process relies on sensors to feedback information and achieves automatic control. II. The Development History of Automobile Sensors In the 1960s, there were only oil pressure sensors, oil sensors, and water temperature sensors on cars. They were connected with meters or indicator lights. After the 1970s, in order to control emissions, a number of sensors were added to help control the vehicle's power system, as the catalytic converters, electronic ignition, and fuel injection devices needed to maintain a certain air-fuel ratio to control emissions during the same period. Until the 1980s, ABS and airbags improved vehicle safety. The Development History of Automobile Sensors Sensors are used today to determine the temperature and pressure of various fluids, such as intake temperature, air inlet pressure, cooling water temperature, and fuel injection pressure, and sensors used to determine the speed and position of various parts (such as speed, throttle opening, camshaft, crankshaft, angle and speed of the transmission, the position of the exhaust recirculation valve (EGR), etc.); and for measurement. Sensors for engine load, detonation, broken fire, and oxygen content in exhaust gas; sensors to determine the seat position; sensors to determine wheel speed, road elevation difference, and tire pressure in the anti-lock braking system and suspension control device; and to protect the airbags of the front occupants, not only need more collision sensors and acceleration sensors. The researchers also use the anti-collision sensors (ranging radar or other ranging sensors) to determine and control the lateral acceleration of the car, the instantaneous speed of each wheel and the required torque, so that the braking system is a part of the vehicle stability control system. III. Types of Automobile Sensors and Their Functions (1)According to the relationship of energy, sensors can be classified into two types: active and passive based on their energy relations. Most of the sensors used in cars belong to passive sensors, which require additional input power to produce electrical signals, so the sensor is actually an energy controller. (2)According to the classification of signal conversion according to the signal conversion classification, it can be divided into one kind of non electricity conversion into another kind of non electricity, such as elastic sensitive element and pneumatic sensor; the other is the transducer converted from non electricity to electricity, such as thermocouple temperature sensor, piezoelectric accelerometer and so on. (3)Classification according to input quantity according to input quantity is classified according to the measurement, which can be divided into displacement, velocity, acceleration, angular displacement, angular velocity, force, torque, pressure, vacuum degree, temperature, current, gas composition, concentration sensor and so on. For example, the following air flow sensor: Air flow sensor (4)According to the working principle classification according to the working principle of the sensor, there are resistance, capacitance, strain, inductance, photoelectric, photosensitive, piezoelectric, thermoelectric sensor, etc. (5)According to the output signal classification, according to the sensor output signal, there are analog and digital sensors. Simulation system adoption and digital system adoption IV. Sensors Used in Automobile Engines and Their Functions Electronic control of engines has been considered to be one of the main technology fields of automobiles. The sensor of engine control system is the core of the whole automobile sensor, and there are many kinds, including temperature sensor, pressure sensor, position and speed sensor, flow sensor, gas concentration sensor and detonation sensor, etc. These sensors provide the engine's work condition information to the engine's electronic control unit for accurate control of the engine working condition, in order to improve engine power, reduce fuel consumption, reduce exhaust emissions and perform fault detection. Sensors Used in Automatic Inductive Door 4.1 Automobile Temperature Sensor Temperature sensor like automobile temperature sensor is mainly used to detect engine temperature, suction gas temperature, cooling water temperature, fuel temperature, and catalytic temperature. Water temperature state indicatior The temperature sensor has three main types: thermistor, wire wound resistor, and thermal couple resistor. These three types of sensors have their own characteristics, and their applications are also slightly different. The thermistor temperature sensor has high sensitivity and good response characteristics, but it has poor linearity and low temperature. Among them, the universal temperature range is -50 C to 30 C, the precision is 1.5%, the response time is 10ms, the high-temperature type is 600 to 1000, the precision is 5%, the response time is 10ms; the precision of the wire-wound resistance temperature sensor is high, but the response characteristic is poor; the precision of the thermocouple resistance temperature sensor is high and the temperature range is wide, but it needs to be used together with the amplifier and cold end treatment. Other practical products have ferric oxygen sensor (temperature range from -40 to 120, 2%), metal or semiconductor membrane air temperature sensor (temperature range from -40 to 150, 2%, 5%, response time 20ms). 4.2 Automobile Pressure Sensor The pressure sensor is the most used sensor in automobiles. It is mainly used to detect air pressure of airbags, the fluid pressure of transmission system, injection pressure, engine oil pressure, inlet pipe pressure, the fluid pressure of air filtration system, and so on. At present, the more commonly used vehicle pressure sensors are capacitive, piezoresistive, differential transformer, and surface acoustic wave. The capacitive pressure sensor is mainly used to detect negative pressure, hydraulic pressure, and air pressure. The measurement range is 20kPa to 100kPa. Its characteristics are high input energy, good dynamic response characteristics, and good environmental adaptability. The performance of the piezoresistive pressure sensor is affected by temperature, and it needs another temperature compensation circuit, but it is suitable for mass production; the differential transformer type pressure sensor has a large loss. The acoustic surface wave pressure sensor has the characteristics of small volume, lightweight, low power, low power, high reliability, high sensitivity, high resolution, and digital output. It can be used in the pressure detection of the automobile air suction valve and can work steadily at high temperatures. 4.3 Air Flow Sensor The flow sensor is mainly used for measuring the airflow and fuel flow of the engine. The intake volume is one of the basic parameters for fuel injection calculation. The Mass Air Flow Sensor (MAF) is a computer-controlled sensor that calculates the volume and density of the air taken in by the engine. This in turn ensures the right amount of fuel is used for optimized operating conditions. If this sensor is faulty, the car may stall and the fuel usage will be higher than necessary. The function of the airflow sensor is to perceive the size of the airflow and transform it into an electrical signal to transmit to the electronic control unit of the engine. The measurement of airflow is used in the engine control system to determine combustion conditions, control air-fuel ratio, start, and ignition. There are 4 types of airflow sensors: rotary wing, Carmen vortex, hot wire, and hot film. The main technical indicators of the airflow sensor are: the working range is 0.11m3/min to 103m3/min, the working temperature is -40 to 120 degrees, and the accuracy is more than 1%. 4.4 Fuel Flow Sensor The fuel flow sensor is used to detect the flow rate of fuel, mainly with a water wheel and circulating ball. The dynamic range is 0 ~ 60kg/h, the working temperature is -40 to 120, the precision is 1%, and the response time is < 10ms. The position and speed sensor of position and speed sensor crankshaft and speed sensor is mainly used to detect engine crankshaft angle, engine speed, throttle opening, speed, and so on. It provides a reference point signal for ignition time and injection time and provides an engine speed signal at the same time. 4.5 Engine Speed Sensor Engine Speed Sensor is attached to the crankshaft and monitors the spinning speed of the crankshaft, which controls the fuel injection and timing of the engine. Electromagnetic crankshaft position sensor At present, the position and speed sensors used in automobile are mainly AC generator type, magnetoresistance type, Holzer effect type, reed switch type, optical type, semiconductor magnetic transistor and so on. The measurement range is from 0 to 360 degrees, the precision is better than 0.5 degrees, and the bending angle is up to 0.1 degrees. There are many kinds of speed sensors, such as sensitive wheel rotation, sensitive power transmission shaft and sensitive differential driven shaft. When the speed of the vehicle is higher than 100km/h, the general measurement error is larger. The non contact photoelectric speed sensor should be used, the speed range is 0.5km/h to 250km/h, the repetition precision is 0.1%, and the distance measurement error is better than 0.3%. 4.6 Gas Concentration Sensor-oxygen Sensor A gas concentration sensor is mainly used to detect gas and exhaust emissions in vehicle bodies. The most important thing is the oxygen sensor. It detects the oxygen content in the exhaust gas of the car. According to the oxygen concentration in the exhaust, the air-fuel ratio is measured, and the feedback signal is sent to the microcomputer control device to control the air-fuel ratio to converge to the theoretical value. The commonly used germanium oxide sensors (using the temperature of -40 to 900, 1%), chromium oxide concentration cell type gas sensor (using temperature 300 to 800 C), solid electrolyte chromium oxide gas sensor (using temperature 0~400, precision 0.5%), and two oxide oxygen sensor and two oxidation oxygen sensor. The Oxygen sensor measures the amount of unburdening oxygen that is present in the exhaust pipe and will indicate if the fuel is burning rich or lean. A faulty oxygen sensor will cause the car to idle poorly and jerk as well as cause high fuel consumption. Gas concentration sensor Compared with the germanium oxide sensor, the titanium dioxide oxygen sensor has characteristics like basic structure, lightness, cheapness, and strong resistance to lead pollution. The two zirconia micro ion sensor consists of calcium oxide stable oxidation plasma, porous platinum thick film working electrode, palladium/oxidation, and thick film parameter electrode, water layer, electrode contact, and guard layer. titanium dioxide oxygen sensor Among them, the stable oxidation of calcium oxide is deposited by reactive sputtering. Working electrodes and reference electrodes are made by thick film technology. The output voltage of the ideal A/F point is abrupt, the ratio of air to air is higher, the output voltage of the oxygen sensor decreases when the oxygen concentration is added in the exhaust gas; when the air-fuel ratio becomes lower and the oxygen concentration in the exhaust gas decreases, the output voltage of the oxygen sensor is increased. The electronic control unit recognizes the mutation signal and corrections the injection volume, so as to adjust the air-fuel ratio accordingly and make it change near the ideal air-fuel ratio. At present, the NOx sensor is more and more strict for the diesel exhaust emission of NOx and PM. To cope with this limitation, it is not enough to improve the combustion mode of diesel engines. Therefore, post-processing technology is more and more valued. The selective reduction catalyst (SCR) method is one of the NOx purification techniques. The NOx in the tail gas can be selectively adsorbed to the catalyst. By spraying urea to the catalyst, the NOx can be decomposed into nitrogen, water, and discharge by reduction reaction. The sensor in urea SCR can detect whether the dosage of urea water needed for SCR is suitable. This sensor is essential for reducing agents using nitrogen oxides (NOx) as urea water purifiers. Knock sensor detonation sensor is used to detect engine vibration, by adjusting ignition advance angle and avoiding detonation. Detonation can be detected in three ways, namely cylinder pressure detection, engine block vibration, and combustion noise. The detonation sensors have magnetostrictive and piezoelectricity. The use temperature of the magnetostrictive detonation sensor is -40 C ~125 C and the frequency range is 5~10kHz; the piezoelectric detonation sensor has a sensitivity of 200mV/g at the center frequency 5.417kHz and has good linearity in the range of 0.1g~10g. titanium dioxide oxygen sensor has characteristics like basic structure, lightness, cheapness, and strong resistance to lead pollution. The two zirconia micro ion sensor consists of calcium oxide stable oxidation plasma, porous platinum thick film working electrode, palladium/oxidation, and thick film parameter electrode, water layer, electrode contact, and guard layer. V. Application of Vehicle Sensor in Vehicle Chassis Electronic Control System Chassis sensors are sensors distributed in the transmission control system, the suspension control system, the power steering system, and the braking system. They are different in different systems, but the working principle is the same as the sensor in the engine, which is mainly used in the following. Suspension sensors are used to control and control vehicle dynamics by interfering and adjusting the characteristics of vehicle suspension components. The continuous damping control system (ADC) consists of 4 control units, CAN, 4 wheel vertical acceleration sensors, 4 body vertical acceleration sensors, and 4 damper proportional valves. According to the vehicle movement and the information detected by these sensors, the optimal damping coefficient of each wheel suspension damper is calculated, the height of the car is adjusted automatically, the change of the vehicle posture is suppressed, and the control of vehicle comfort, handling stability and driving stability is realized. The system is realized by the electronic control of the steering angle of the wheel. The common system has the active front-wheel power steering system ESP, the active front-wheel superposition steering system AFS, and the active rear-wheel steering system RWS. The sensors used mainly include the speed sensor, engine speed sensor, torque sensor, and so on, which make use of these sensors to make the power steering control system realize steering control light, improve response characteristic, reduce engine loss, increase output power, save fuel and so on. Whether it is ESP, AFS, or RWS, the principle of it is the driver's manipulation instruction, which senses the condition of the road surface by the sensor, and passes the network to the electronic controller and the actuator in the form of the electrical signal. (1)The anti-lock braking sensor of the ABS system mainly uses the wheel angular velocity sensor to detect wheel speed. When the slip rate of each wheel is 20%, the brake oil pressure is controlled, the braking performance is improved, and the vehicle handling and stability are ensured. In this system, the wheel speed sensor is a very important part of ABS. It needs to provide reliable and precise wheel speed to ECU in time. The sensors have electromagnetic, Holzer, and magnetoresistance. (2)TCS system, when the driving torque of the vehicle driving wheel is too large, the driving wheel will move relative to the ground. It is generally hoped that the slip rate of the driving wheel should not exceed 20%. This system of control for driving wheel skating is called the TCS system. It is developed on the basis of ABS. In most cars, TCS and ABS share an ECU. They identify and judge the driving condition of a vehicle based on the signal input by sensors. (3)ESP electronic stabilization system ESP is an active safety system with good maneuverability and direction stability by adjusting the size and matching of the longitudinal force of the wheel to control the yaw motion of the car. The basic principle of ESP is to identify the expected motion state of a driver by means of sensors and operational logic. In order to identify the driver's expectation of the car and know the actual motion state of the car, the ESP system needs more sensors than ABS and TCS. They are hydraulic sensors of steering wheel sensor, vehicle yaw rate sensor, lateral acceleration sensor, and brake master cylinder. VI. Sensor Application in Automobile Safety System Safety is the primary factor for automobile consideration, and there are many sensors for safety, such as micro accelerometers for automobile airbags, surface micromachined gyroscopes of angle measurement rate, etc. Microaccelerometer micro accelerometer is usually composed of a parallel cantilever beam, one end of the beam is fixed on the frame and a small mass block (about 10mg) is suspended at the other end. When there is no acceleration, the mass block is not moving. When there is a vertical acceleration, the mass block is moving, the acceleration is sensitive to the acceleration, and the signal is converted to the output by C/V transformation and phase-sensitive demodulation. According to the detection mode, the micro accelerometer has several kinds of piezoresistive, capacitive, tunnel, resonant, and thermal forms. The capacitance micro accelerometer has high sensitivity, low noise, small drift and a simple structure. It is widely used in automobile airbag systems and anti-skid systems. The mass of capacitance micro accelerometer mass block moves downward when it has acceleration and changes the distance from another electrode on the frame. The displacement of mass movement can be obtained by measuring the change of capacitance. The main structure is divided into suspension. The arm swing type and comb-like folded beam type are changed into other types. The structure of the former is relatively simple, and the bulk silicon processing method is mostly used. The simple pendulum type structure consists of the upper and lower fixed electrodes and the movable sensitive silicon cantilever beam electrode, the anisotropic corrosion of the semiconductor plane process, and the encapsulation of the electrostatic sealing technology. The latter can be regarded as the combination of the cantilever beam and the combination. The design is much more complicated. The micromachining method is mainly based on surface sacrificial layer technology. The isotropic properties of the polysilicon material can guarantee the symmetry of the micromechanical properties, the precision of the batch processing is high, and the sensitive parts of this structure are small in size, and the monolithic integration of the peripheral circuits is realized. Micromachined gyroscope (MEMS) micromachined gyroscope (MEMS) is a vibrational angular rate sensor, which has attracted much attention in the application and development of automobiles. It is mainly used in GPS signal compensation and chassis control system for automobile navigation. There are two vibration modes in the micromechanical gyroscope, one is the transverse vibration mode, that is, the mode of driving vibration, which is usually called the reference vibration, which will produce additional motion under the action of the Coriolis force; the other is the normal vibration mode, the sensitive vibration mode, the detection of the additional movement of the Coriolis force, and the angular rate information contained in the Coriolis force. According to the material used, the micromachined gyroscope is divided into two kinds of quartz and silicon vibrating beams. The quality factor of quartz material has the highest Q value, the top characteristic of the gyroscope is the best, but the quartz processing is difficult and the cost is very high. Silicon material has complete structure, good elasticity, and easy to get high Q value micromechanical structure, which has become the mainstream of low-cost research and development at present. The structure of the silicon micromachined gyroscope, the vibration beam structure, the double frame structure, the plane-symmetric structure, the transverse fork structure, the comb tuning fork structure, the beam island structure are used. The driving modes for the reference vibration are electrostatic, piezoelectric, and electromagnetic driving. The detection methods of additional vibration caused by the Coriolis force are capacitive detection, piezo detection, and piezoresistive. Testing. The gyroscope design with electrostatic drive and capacitance detection are the most common. Some of the products have been developed successfully. Vehicle monitoring and self-diagnosis sensor in-vehicle monitoring and self-diagnosis, the main application of vehicle sensors will be tire pressure monitoring, followed by sensors applied to cooling, braking, and other systems. In addition, such as the use of light sensors in the luminance control system, the use of magnetic sensors and airflow velocity sensors in the driving system, the use of indoor temperature sensors, suction temperature sensors, air volume sensors, sunshine sensors, and humidity sensors in the automatic air conditioning system, and the use of azimuth sensors and speed sensors in the steering system. The collision sensor is the main control signal input device in the airbag system. The effect is when the vehicle collides on the road, the collision sensor is used to detect the intensity signal of the car collision, and the signal is entered into the airbag computer. The airbag computer determines whether the inflatable element is detonated to inflate the airbag according to the signal of the collision sensor. After the transformation of many countries, many cars are also equipped with side airbags. When the car has a lateral collision, the airbag will also be inflated, so a system equipped with a lateral airbag is equipped with a collision sensor on the left and right sides of the car. This is more humane in ensuring the safety of vehicle users. The lateral tilt angle sensor is an effective method to prevent the car from turning over the car during driving. It is an important measure to improve the safety of the car, especially the high gravity cars, such as the off-road vehicle and the double-deck passenger car, which is more necessary. Take an example, an angle sensor made with the principle of gravity. The mass of the swing part is m, and the distance between the center of gravity and the shaft is L. When the car body tilts or curves, it can make the swing part deflect. The force analysis in Figure 1 is an ideal state without any friction. The force F is the result of the joint action of the sliding force F1 and the centripetal force F2. The force F is proportional to the tilting force, and the beta-generated deflection angle is proportional to the tilting force. The resultant force T of the gravitational G and F in the oscillating part is the tension of the pendulum, and the swing angle of beta =tg-1 (F/G) is independent of L. When the mass m is fixed, the beta is only related to F and is proportional. In fact, due to the existence of friction on the shaft, the longer the L is, the larger the swing torque is, the higher the accuracy. Angle sensor is usually used as a sampling element in the control system, and its performance plays an important role in the whole system. The potentiometer angle sensor has been widely used in all kinds of control systems, but its disadvantage is the existence of sliding wear and electrical noise of the contact. The magnetic sensitive resistance angle sensor is a new pure resistive element made of semiconductor technology. It is characterized by no contact. When the swing partial deflection, the flux of the magnetic resistor is changed to make the resistance of the magnetic sensitive resistance several times. The above changes fundamentally eliminate the electrical noise and improve the accuracy. All kinds of angle sensors have a damping function so that there is a short delay in response to the measured angle, which is beneficial for the control system. VII. Other Major Automotive Sensors Alcohol detection MEMS system is a new type of integrated alcohol sensor, which can adsorb oxygen according to the oxygen concentration in the environment and change the resistance value. In normal conditions, the element can keep a certain resistance value after the oxygen is adsorbed in the air, and once the air contains alcohol, the oxygen element on the surface of the element will react with the alcohol to reduce the resistance value. By measuring the resistance value, we can detect the alcohol concentration in the breath. The alcohol detection MEMS sensor will be embedded in the sealed shell of the diameter 8mm, together with the signal processing circuit and so on, and will be embedded in the steering wheel together. Once the driver's exhaled gas contains alcohol, a safety alarm will be issued. When the raindrop is hit on the glass of the induction zone, the intensity of the light reflected by the raindrop will change because of the rainfall or moisture content on the glass and changes the brushing frequency of the wiper. Or through the infrared electronic rainfall sensor to induce the amount of rainfall, and automatically adjust the speed of the wiper with the change of speed to improve the driver's driving convenience to make the driving safer. The tire pressure monitoring system installs highly sensitive sensors on each tire to monitor the tire condition at any time in the driving state and transmit it wireless to the receiver through a sensor to enable the driver to grasp the condition of the tire at any time, to ensure the safety of the car, to prolong the service life of the tire and to reduce the consumption of the fuel. The most advanced direct tire pressure monitoring solutions include advanced warning systems, pressure, temperature, voltage and motion detection. When the oil viscosity sensor changes the oil, it usually depends on the time or mileage specified by the manufacturer. A few manufacturers have adopted a more advanced way to calculate the oil exchange interval by recording engine speed and temperature. VIII. Automotive Sensors Market Size--Its Market Trend Because of the important role of automotive sensors in the automotive electronic control system and the rapid growth of the market demand, all countries in the world have paid great attention to its theoretical research, new material application, and new product development. The development trend of automotive sensor technology in the future is miniaturization, multi-function, integration, and intelligence. The microsensor with low cost and high performance can be designed by means of micro electro mechanical system (MEMS) technology and computer-aided design technology. At the current level of technology, micromachining technology has been able to produce microstructures with different levels of 3D, and then produce tiny sensor sensors with very small sizes. Because the components are relatively small, the use is relatively convenient and efficient, making the economy improved. Multifunction means that a sensor can detect 2 or more two characteristic parameters or chemical parameters, thus reducing the number of sensors and improving the reliability of the system. Integration refers to the use of IC manufacturing technology and fine processing technology to make IC sensors. Intelligentization refers to the combination of sensors and large-scale integrated circuits with CPU, which is intelligent, to reduce the complexity of ECU, to reduce its volume, and to reduce the cost. In addition, the development of new materials is an important basis for sensor technology. Now new materials, such as optical fiber, nanomaterials, superconducting materials, have opened a new world for the development of sensors. With the development of research, more and more new sensor materials will be developed. The function of the sensor is not only related to its material, but also to its processing technology. Micromachining technology has been increasingly used in the sensor manufacturing process. With the development of modern manufacturing technology, more advanced manufacturing technologies will be applied to the manufacture of automotive sensors. The principle of the sensor is based on various physical, chemical, biological effects, and laws, which enlightens people to further explore sensitive functional materials with new effects and to develop new sensors with new principles. This is an important way to develop low-cost, high-performance, multi-functional, and miniaturized sensors. FAQ 1. What is a sensor in automobile? Automobile sensors are intelligent sensors which can be used to control and process the pressure of oil, temperature, level of emission, coolant levels, etc. There are different types of sensors used in automobiles, but knowing the working of these sensors is essential. 2. How many sensors does a car have? Currently, each vehicle has from 60 to 100 sensors on board and we can expect that number to rise as cars get 'smarter'.” In fact, recent industry figures suggest the number of sensors is projected to reach as many as 200 per car based on current trends. 3. What is the importance of sensors in the automobile? Sensors monitor vehicle engines, fuel consumption and emissions, along with aiding and protecting drivers and passengers. These allow car manufacturers to launch cars that are safer, more fuel efficient and comfortable to drive. 4. How do vehicle sensors work? Using echo-times from sound waves that bounce off nearby objects, the sensors can identify how far away the vehicle is from said object, and alert the driver the closer the vehicle gets. Electromagnetic sensors create an electromagnetic field around the bumper, and offer an alert whenever objects enter it. 5. How many sensors does a F1 car have? 300 sensors. With help from over 300 sensors on each car, McLaren's F1 ECU deals with over 1000 input parameters and transmits more than 1.5GB of live data back to the garage during an average 300km grand prix. 6. Where are sensors located on cars? Depending on the vehicle engine model, you often have 1 to 4 exhaust gas temperature sensors. The sensors are installed on the exhaust pipe and the exhaust manifold, and sometimes also on the turbocharger. The sensors are often quite expensive and can be difficult to reach and replace; they often rust and get stuck. 7. How long do car sensors last? Newer oxygen sensors are supposed to work efficiently for 60,000 to 90,000 miles, depending on the model of your car. If your mechanic determines that your car's problem is due to a bad or failing oxygen sensor, the replacement shouldn't take long and you'll be ready to tackle many more miles on the road. 8. Do all cars have sensors? Modern cars have an increasing amount of sensors. Most cars have an oxygen sensor and a throttle position sensor, but parking sensors are optional. Professional mechanics agree that one of the most important evolutions to come about in recent years is the expansion of sensors to monitor mechanical systems. 9. How do I know if my upstream or downstream oxygen sensor is bad? A decrease in fuel efficiency can be a telltale sign that an O2 sensor is not performing as it should. This can happen because of a fuel mixture that is either too lean or too rich. Such a swing in A/F ratio is a sign that an upstream or control sensor is faulty. 10. What does a car do when the oxygen sensor is bad? If your oxygen sensor is failing, then its readings will be inaccurate, again, resulting in a sub-optimal fuel-to-air composition. Your car's performance isn't the only thing that is harmed by a malfunctioning oxygen sensor - it can do damage to the environment as your car's emissions will increase drastically.
kynix On 2018-04-02
Radio Frequency Identification (RFID) technology has been developed rapidly in recent years. The key is an automatic identification technology which uses radio waves to communicate. Compared with the traditional recognition technology, it has the advantages of fast recognition, large data storage and data updatable. This is a video about brief introduction to RFIDThe basic principle of the data communication is the electromagnetic coupling between the reader and the electronic tag affixed to the object. This article will take the RFID technology as the research object, analyzing the basic definition of RFID, the components of the system, the working principle, operating frequency, the main application examples and development trend of RFID technology. In this article, we will make some intorduction to RFID and analyze how it will develop in the future. CatalogI What is RFID?II Structure of RFID system2.1 Basic components of RFID2.2 RFID middlewareIII Basic working principle of RFID technologyIV RFID operating frequency4.1 Low frequency 4.2 High Frequency4.3 Ultra-high frequency4.4 Active RFID technologyV RFID practical application examples5.1 Necessity of applying RFID technology to retail logistics5.2 Why to use RFID technology instead of existing technology5.3 Application of RFID technology in retail industryVI Development trend of RFID application system6.1 More powerful system compatibility6.2 System networking6.3 Greater system data volume6.4 High frequency systemFAQI What is RFID?Radio Frequency Identification (RFID) technology, also known as electronic tag, is a communication technology that uses radio signals to identify specific targets and read and write related data. And there is no need to identify the mechanical or optical contact between the system and the specific target. It can achieve fast reading and writing, non-visual recognition, mobile recognition, multi-target recognition, locating and long-term tracking management. The recognition work is not affected by bad environment, and it can achieve fast reading speed, read information safe and reliable. Therefore, RFID technology has a wide range of application prospects. Radio frequency identification is a non-contact automatic identification technology. It can automatically identify the target object and obtain the relevant data through the radio frequency signal. The identification work can be applied to all kinds of bad environment. RFID is a simple wireless system with only two basic devices. It is used to control, detect and track objects. The system consists of an interrogator and many transponders.Due to the rapid development of RF technology, transponders are also called smart tags or tags. The RFID reader can communicate wirelessly with the electronic tag through the antennas, and can read and write the tag identification code and memory data. A typical reader includes a high-frequency module, a control unit and a reader antenna. II Structure of RFID system2.1 Basic components of RFIDRFID system mainly includes four parts: electronic tag, reader, antenna and application software. The following picture is the block diagram of the system:RFID system structureFrom the above diagram, we can see that there are input and output of data in the module of reader and electronic tag, and the energy and clock are also transmitted in the two modules.2.1.1 ReaderReader is a device for reading (or writing) tag information that can be designed to be hand-held or fixed type. Hand-held is a smaller type used by supermarket cashiers; Fixed is a stationary reader placed by a logistics company at the door when goods are stored in a warehouse. As soon as the object swept by, the scan was completed in an instant.Reader working model2.1.2 AntennaAntenna is used to transmit RF signals between tags and readers.2.1.3 TagsTags are made up of coupling elements and chips. Each tag has a unique electronic code attached to an object to identify the target object. The following picture is the query tag diagram of readers. Reader query tag diagram2.1.4 Application softwareApplication software is a part of RFID system, which is software developed for different needs. It can read, write and control electronic tags through readers, and process and count the collected data. 2.2 RFID middlewareIn the application program, the API can connect to the RFID reader and retrieve the data from the RFID tag through the universal application program interface which can be provided by middleware. RFID middleware acts as a bridge between RFID tags and applications.In this way, even when the FRID reader category or application changes, the application still doesn't need to make any changes. It just need to configure the middleware accordingly. This can reflect the flexibility and importance of middleware.Practical application of RFID middlewareThe benefits that the application of RFID middleware can be brought to an enterprise are as follows:- According to their own business requirements and actual usage, enterprises can import the required data into the application software by self-configuring the RFID middleware parameters, which can fully reflect the flexible characteristics of RFID middleware.- The import of RFID data only needs to change the setting of RFID middleware when some changes occur in enterprise application software.- If you need to increase the number of RFID readers, then enterprises only need to do some related RFID middleware settings. It doesn’t need to change any related procedures, which reduce unnecessary trouble, and save time.- It shortens the implementation cycle of RFID application, and enterprises can directly import the relevant data of RFID. III Basic working principle of RFID technologyA complete RFID system is composed of three parts: reader, tag with transponder and application software system. Its working principle is: Reader sends out the energy of a radio wave at a specific frequency to drive the transponder, and the circuit will send out the internal data. At this time, the reader will receive the data in order and interpret them, then send it to the application for some corresponding processing.RFID working principleThe information exchange between the reader and the transponder is usually half-duplex communication mode. In this case, the reader can provide the passive transponder with energy, timing and other related contents by coupling. In practical application, the object recognition information can be collected, processed and transmitted remotely through Ethernet and so on. Transponder is the main information carrier of its system. At present, most of the transponders in the market are composed of coupling elements (including coils, microstrip antennas, etc.) and passive application units composed of microchips. The reader can control and process the information center according to the structure and technology of RFID system information. Its reader is usually composed of a transceiver module, a coupling module, an interface unit and a control module. IV RFID operating frequencyAt present, the operating frequencies of RFID products are divided into low frequency, high frequency, ultra high frequency and so on. RFID products with different frequencies will have different characteristics. 4.1 Low frequency (125KHz ~ 135KHz)Related operation at this frequency is mainly done by inductive coupling. There is a transformer coupling between the inductor coil and the reader coil. The voltage which can be induced in the antenna of the inductor can be rectified by the action of the relative alternating field of the reader. Features:- Apart from some related effects of metal materials, the general low-frequency system can penetrate any material, but it will not reduce its maximum possible reading distance.- Readers working at low frequencies have no special licensing restrictions on the entire planet.- Low-frequency products have different packaging forms. The disadvantage of the best package is that it is too expensive, but it has a service life of more than 10 years.- The frequency of the sensor working in low frequency ranges from 120KHz to 134 kHz. The wavelength of this band is about 2500m. 4.2 High frequencySensors at this frequency will no longer need a coil to wrap it up. Antennas can be made by etching or printing. The related operations of sensors are usually done by load modulation. That is, by turning on and off the load resistance on the inductor, the voltage on the reader antenna will be changed, which can realize the amplitude modulation of the antenna voltage with the remote inductor. If people use data to control load voltages on and off, the data can be transmitted quickly from the sensor to the reader.Features: - Apart from metallic materials, the wavelength of this frequency can pass through most materials, but it will reduce the reading distance. Sensors often need a distance away from the metal.- Although the magnetic field region at this frequency decreases rapidly , a relatively uniform read - write region can be produced.- The system has good anti-collision property and can read many electronic tags at the same time.- Sensors usually exist in the form of electronic tags. 4.3 Ultra-high frequencyThe ultra-high frequency system will transmit energy by electric field. The energy of the electric field will not decrease rapidly. The reading distance of UHF is relatively long, and the passive system can reach about 10m. It is mainly realized by capacitive coupling.Features: - This frequency band has a good reading distance, but it is difficult to define the reading region.- It has a particularly high rate of data transmission and can read a large number of related electronic tags in a very short time.- The radio waves in the UHF band cannot pass through many kinds of application materials, especially water, dust and other substances. For high-frequency electronic tags, however, the tags need not be separated from metals.- Tag antennas are usually in two forms: long stripes and tags. The antenna has two different shapes: linear and circular polarization. It is designed to meet the needs of different applications in the market. 4.4 Active RFID technologyActive RFID is characterized by large amount of data transmission, long communication distance, high reliability, low transmitting power and good compatibility. Compared with passive RFID, it has obvious technical advantages.The basic ideas of RFID technology are: By adopting advanced technical means, people can automatically identify and manage all kinds of objects and equipment in different states.As a new kind of automatic identification technology, RFID technology has a great potential space for development in China, and it has been applied and developed in radio technology. V RFID practical application examplesIn this chapter, we will mainly expound the logistics analysis of retail industry based on RFID technology.5.1 Necessity of applying RFID technology to retail logisticsThe benefits of using RFID technology are not limited to the benefits of retail itself. With the use of RFID technology to create a new revenue stream, government institutions can reduce the loss and enhance the safety and security. At the same time, logistics companies, library systems can also reduce inventory costs.The application of RFID technology in retail can obtain the following benefits: - Increase project securityTag items only allow objects to be tracked in a specified range or device. RFID technology can also improve the efficiency of inventory management. After all, inventory management is often a time-consuming and exhausting business for retailers. - Serialization DataEach item has its unique identification number, so it is convenient to distinguish it from other items. - Real time information flowThe changing state of a project can be quickly updated throughout the supply chain. - Reduced manual participationRFID technology can track objects automatically without manual counting , data acquisition and bar code scanning , which can save labor cost and human error. The RFID technology provides a real-time visualization technology that allows inventory managers to monitor inventory supplies in real time. This reduces inventory costs and keeps inventory at an optimal level, which avoids shortage and other phenomena at the same time. 5.2 Why to use RFID technology instead of existing technologyThe question now is: why did retail change existing technology by adopting RFID? RFID technology is very similar to the existing bar code technology and non-contact memory. The use of new technologies can bring financial benefits (such as saving money) and can solve some practical problems that can not be solved by the existing technology. Compared with other automatic recognition techniques, RFID has significant advantages. 5.3 Application of RFID Technology in Retail industryRFID technology has been used in the retail industry such as smart shelf. The smart shelf is a kind of shelf which can prevent the phenomenon of product shortage. The shelf combines the RFID reader. Each unit shelf has a RFID tag that allows readers to track the inventory of their products. The main purpose of smart shelf is to support the replenishment at any time and to keep the shelves never out of stock, thus it has been widely used in retail industry and libraries. On one hand, it provides customers with information about the products; on the other hand, it provides inventory information for retail owners and can accurately locate the goods. The purpose of these applications is to offer better and more effective service to them. The use of these technologies will not be limited. It can make customers feel more effective and easier to shop.VI Development Trend of RFID Application systemIt can be predicted that future RFID systems will have the following technological trends: 6.1 More Powerful System CompatibilityAt present, because of the disunity of standards, products from many manufacturers are incompatible with each other. Therefore, it is required that the system should have a very strong compatibility, so that it can deal with the products of multiple manufacturers. 6.2 System NetworkingIn many applications, the data collected by different systems need to be processed uniformly, and then provided to users for use, which requires the management of RFID systems on a networked basis. The aim is to realize the remote control management of the system. 6.3 Greater System Data VolumeThe future RFID system will deal with a large amount of data, so it is necessary for the system to have a stronger data storage capacity and data processing capacity. 6.4 High frequency systemThe UHF RFID system has many advantages compared with the low frequency system, such as small size, long recognition distance, repeatable reading and writing, and no forgery. Therefore, with the decrease of manufacturing cost, the application of UHF system will be more extensive. FAQ 1. What is RFID used for?Radio Frequency Identification (RFID) is the wireless non-contact use of radio frequency waves to transfer data. Tagging items with RFID tags allows users to automatically and uniquely identify and track inventory and assets. 2. What is RFID and how it works?RFID is a method of data collection that involves automatically identifying objects through low-power radio waves. Data is sent and received with a system consisting of RFID tags, an antenna, an RFID reader, and a transceiver. 3. What RFID means?Radio Frequency Identification (RFID) refers to a wireless system comprised of two components: tags and readers. The reader is a device that has one or more antennas that emit radio waves and receive signals back from the RFID tag. 4. Is RFID harmful to human?It is a non-ionizing type of radiation, but some researches show that it could have a negative impact on the human body in a long-term period [11, 12]. So, for the safety reasons, manufacturers of the RFID systems have limited the range of the RFID antennas used in their systems. 5. Is RFID tag and FASTag same?FASTag is a device that employs Radio Frequency Identification (RFID) technology for making toll payments directly while the vehicle is in motion. FASTag (RFID Tag) is affixed on the windscreen of the vehicle and enables a customer to make the toll payments directly from the account which is linked to FASTag. 6.What is RFID and its advantages?RFID technology automates data collection and vastly reduces human effort and error. RFID supports tag reading with no line-of-sight or item-by-item scans required. RFID readers can read multiple RFID tags simultaneously, offering increases in efficiency. 7. Why is RFID bad?Some negative effects are that its deadly, if RFID tags combine with static electricity you can die. Another negative effect is that the government is slowly taking away surviving resources and giving ultimatums, such as if you don't get the RFID tracking chip your public assistance will be terminated. 8.What are the disadvantages of RFID?a. Materials like metal & liquid can impact signal.b. Sometimes not as accurate or reliable as barcode scanners.c. Cost – RFID readers can be 10x more expensive than barcode readers.d. Implementation can be difficult & time consuming. 9.How do I charge my RFID FASTag?In order to recharge your FASTag sticker, just hit the Add Money option in your Paytm app. FASTag will automatically reserve some amount from your wallet, which can be used at toll plazas later. Do note that FASTag can be used only after 20 mins of adding money to the Paytm Wallet. 10. Can I use existing RFID for FASTag?If a vehicle already has an RFID tag, it might already be activated. When you buy the vehicle, RFID tag payment was also done. It might also have a minimum balance of INR 100 or 200 as is required by the bank. You can recharge it with your Customer ID or Wallet ID of FASTag. 11. How does RFID work without power?Passive RFID tags have no power of their own and are powered by the radio frequency energy transmitted from RFID readers/antennas. The signal sent by the reader and antenna is used to power on the tag and reflect the energy back to the reader. 12. What are the types of RFID tags?RFID tags can be grouped into three categories based on the range of frequencies they use to communicate data: low frequency (LF), high frequency (HF) and ultra-high frequency (UHF). Generally speaking, the lower the frequency of the RFID system, the shorter the read range and slower the data read rate. 13.How do I know if I have an RFID chip?The best way to check for an implant would be to have an X-ray performed. RFID transponders have metal antennas that would show up in an X-ray. You could also look for a scar on the skin. Because the needle used to inject the transponder under the skin would be quite large, it would leave a small but noticeable scar. 14. Does RFID require power?Active RFID tags possess their own power source – an internal battery that enables them to have extremely long read ranges as well as large memory banks. Typically, active RFID tags are powered by a battery that will last between 3 - 5 years, but when the battery fails, the active tag will need to be replaced. 15. What is the difference between a QR code and RFID?QR codes must always be “read-only”, whereas RFID tags can be “read-write”, depending on the radio frequency that's being used. ... So, not only are RFID tags futuristic and have more uses than QR tags, they also have many more applications. The read range is far superior for an RFID tag.
kynix On 2018-03-29
Warm hints: this article reading time is about 15 minutes. This article is mainly about learning several kinds of industrial weapons - sensors. Automation technology is a comprehensive technology. It has a very close relationship with cybernetics, information theory, systems engineering, computer technology, electronics, hydraulic pressure technology, and automatic control, among which automation is based on control theory and computer technology. CatalogI、Automation TechnologyII、Physical SensorIII、Fiber Optic SensorIV、Bionic SensorV、Infrared SensorVI、Electromagnetic SensorVII、Magneto-optical Effect SensorVIII、How to Choose Industrial SensorsFAQ I. Automation Technology Automation technology is a comprehensive technology. It has a very close relationship with cybernetics, information theory, system engineering, computer technology, electronics, hydraulic pressure technology, automatic control, etc., of which automation and control theory and computer technology The most influential technology. There are a lot of special equipment in automation technology, just like the different weapons, the author made a count of the automated weapons below.II. Physical SensorPhysical sensorSensor (Sensor) is a common but very important device. A sensor is a device, module, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. For the sensor, the input can be divided into static and dynamic according to the input state. We can get the static characteristics of the sensor based on the relationship between the output and the input based on the steady-state of each value. The main indicators of the static characteristics of the sensor are linearity, hysteresis, repeatability, sensitivity, and accuracy. The dynamic characteristics of a sensor refer to the response characteristics of the input over time. Dynamic characteristics are usually described using automatically controlled models such as transfer functions. In general, the signal received by the sensor has a weak low-frequency signal, and the amplitude of the external interference sometimes exceeds the measured signal. Therefore, eliminating the noise in series becomes a key sensor technology. The physical sensor is a sensor that detects physical quantities by the use of certain physical effects. The sensor can convert measured physical volume into a form of energy to facilitate the processing of the signal device. The output signal and the input signal have a definite relationship. The main physical sensors include photoelectric sensors, piezoelectric sensors, piezoresistive sensors, electromagnetic sensors, pyroelectric sensors, and optical fiber sensors. As an example, let us look at the more commonly used photoelectric sensors. This kind of sensor converts the optical signal into an electrical signal. It directly detects the radiation information from the object and can also convert other physical quantities into an optical signal. The main principle is the photoelectric effect: When the light is irradiated to the material, the electrical effect on the material changes, and the electrical effects here include electron emission, conductivity, and potential current. Obviously, a device that can easily produce such an effect becomes a major component of a photoelectric sensor, such as a photoresistor. In this way, we know that the main working process of a photoelectric sensor is to receive the corresponding light, convert the light energy into electricity through a device such as a photosensitive resistance, and then obtain the required output by amplification and denoising electric signal. The output electrical signal here has a certain relationship with the original optical signal, which is usually close to a linear relationship so that the calculation of the original optical signal is not very complicated. The principles of other physical sensors can be compared to optical sensors. The range of applications of physical sensors is very extensive. We look at the application of physical sensors from the perspective of biomedical sciences. It is not difficult to infer that physical sensors have important applications in other aspects. For example, blood pressure measurement is the most common type of medical measurement. Our usual blood pressure measurement is an indirect measure of the blood pressure in the vessel by measuring the relationship between blood flow and pressure detected by the body surface. The sensors needed to measure blood pressure usually include an elastic diaphragm that transforms the pressure signal into a deformation of the diaphragm and then converts it into a corresponding electrical signal based on the strain or displacement of the diaphragm. At the peak of the electrical signal, we can detect systolic pressure. After passing through the inverter and the peak detector, we can get the diastolic pressure. The average pressure can be obtained through the integrator. Let us look again at breath measurement technology. Respiratory measurement is an important basis for the clinical diagnosis of lung function and is essential in surgery and patient monitoring. For example, when using a thermistor sensor for measuring respiratory rate, mount the sensor's resistance on the outside of the front end of a clip, clip the clip over the nose, and pass the heat as the flow of breathing gas flows from the thermistor surface Sensitive resistance to measure the frequency of breathing and the status of hot gas. Another example of the most common body surface temperature measurement process. Although it seems easy, it has a complex measurement mechanism. The body surface temperature is determined by various factors such as the local blood flow, the heat conduction of the underlying tissue, and the heat dissipation of the epidermis. Therefore, the measurement of the skin temperature must take into account various influences. Thermocouple sensors are more commonly used in the measurement of temperature, usually rod-shaped thermocouple sensors and thin-film thermocouple sensors. Because the size of the thermocouple is very small and the accuracy is relatively high, it is possible to measure the temperature at a certain point accurately. With the help of later analysis statistics, a more comprehensive analysis result can be obtained. This is incomparable with the traditional mercury thermometer, but also shows the broad prospects for the application of new technologies to scientific development. From the above introduction, it can be seen that physical sensors have a variety of applications just in biomedical applications. The development direction of the sensor is a multifunctional, imaged, intelligent sensor. Sensor measurement as an important means of data acquisition is indispensable for industrial production and even family life, and physical sensors are the most common family of sensors. The flexible use of physical sensors will inevitably create more products and better benefits. III. Fiber Optic SensorFiber optic sensorIn recent years, sensors have evolved in the direction of sensitivity, precision, adaptability, compactness, and intelligence. In the process, fiber optic sensors are a new addition to the sensor family. Optical fiber has many excellent properties, such as anti-electromagnetic interference and atomic radiation performance, fine diameter, soft, lightweight mechanical properties, insulation, non-inductive electrical properties, water resistance, high-temperature resistance, corrosion resistance, chemical properties, etc. It can reach people's eyes and ears in unattainable places (such as high-temperature areas), or in areas harmful to humans (such as nuclear radiation area), but also can transcend human physiological boundaries and receive sensory organs Unforeseen outside information. Optical fiber sensors are new technologies that have emerged in recent years. It can be used to measure a variety of physical quantities, such as sound fields, electric fields, pressures, temperatures, angular velocities, and accelerations, as well as measurement tasks that are difficult to accomplish with existing measurement techniques. In tight spaces, fiber optic sensors show unique capabilities in environments with strong electromagnetic interference and high voltage. At present, there are more than 70 optical fiber sensors, which are roughly divided into optical fiber sensors and optical fiber sensors. The so-called optical fiber sensor itself is the optical fiber directly to receive the outside world was measured. The external measured physical quantity can cause the length, refractive index, and diameter of the measuring arm to change so that the light transmitted within the fiber changes in amplitude, phase, frequency, polarization, and the like. The light transmitted by the measuring arm interferes (compares) with the reference light of the reference arm to change the phase (or amplitude) of the output light, and the change in the measured light can be detected based on this change. The phase of the transmission in the optical fiber is highly sensitive to external influences, and the interferometric technique can detect the physical quantity corresponding to the slight phase change of 10 negative quadratic arcs. For the optical fiber’s winding and low loss characteristics, we can disc a long fiber optic into a small diameter optical fiber ring in order to increase the length, to obtain higher sensitivity. An optical fiber acoustic sensor is a kind of sensor using the optical fiber itself. When the fiber is a little tiny external force, it will produce micro-bending, and its light transmission capacity has undergone great changes. Sound is a kind of mechanical wave. Its effect on the optical fiber is to stress and bend the optical fiber. By bending, the sound intensity can be obtained. Compared with laser gyro, FOG has high sensitivity, small size, and low cost. It can be used in the high-performance inertial navigation systems of aircraft, ships, and missiles. Another major category of fiber optic sensors is the use of fiber optic sensors. The structure is rough as follows: The sensor is located at the end of the fiber. The fiber is just the transmission line of light, and the physical quantity to be measured is transformed into the change of the amplitude, phase, or amplitude of the light. In this sensor system, conventional sensors are combined with optical fibers. The introduction of optical fibers offers the possibility of implementing probing telemetry. This fiber-optic transmission sensor has a wide range of applications and is easy to use, but its accuracy is slightly lower than that of the first type of sensor. Fiber optic sensors have become a rising star in sensor families with their numerous advantages and have played their own unique role in various measurements and become an indispensable part of the sensor family. IV. Bionic SensorBionic sensorA bionic sensor is a new sensor using a new detection principle, which uses immobilized cells, enzymes, or other bioactive substances and transducers to form a sensor. This kind of sensor is a new type of information technology developed in recent years by the mutual penetration of biomedicine and electronics and engineering. This sensor is characterized by high performance and long life. In bionic sensors, biometric sensors are more commonly used. Bionic sensors in accordance with the media used can be divided into enzyme sensors, microbial sensors, organelle sensors, tissue sensors. In the picture, we can see that there is a close connection between the biomimetic sensor and all aspects of the biological theory and it is a direct result of the development of the biological theory. Among biosensors, urea sensors are a recently developed type of sensor. The following is an example of a urea sensor biosensor sensor application. The urea sensor is mainly composed of two parts, a biofilm, and an ion channel. The biofilm can feel the effects of external stimuli, the ion channel can receive the information of the biofilm and amplify and deliver it. When the sensory site inside the film is affected by an external stimulating substance, the permeability of the membrane will change, allowing a large number of ions to flow into the cell to form the transmission of information. Among them, the important component of the biofilm is the membrane protein, which can produce a conformal network change, change the permeability of the membrane, and transmit and amplify the information. The biofilm ion channels, which are composed of amino acid polymers, can be replaced by polymers of polyamine acids (L-glutamic acid, PLG), which are easily synthesized in organic chemistry, and are more chemically stable than the enzyme. PLG is water-soluble, which is not suitable for motor modification. However, PLG and polymer can synthesize block copolymers to form sensor films for sensors. The principle of the ion channel of the biofilm is basically the same as that of the biofilm. After the block copolymer film is fixed on the electrode, if a substance that changes the inductive network of the PLG is added, the permeability of the film changes, and thus a current is generated. Changes in the current from the changes can be carried out on the detection of stimulating substances. The urea sensor has been tested and proved to be a biometric analog sensor with good stability. The lower limit of detection is 10 orders of magnitude of a negative third power. It can also detect irritant substances, but for the time being it is not suitable for the measurement of living organisms. At present, although many biomimetic sensors have been developed successfully, the stability, reproducibility, and mass productivity of biomimetic sensors are obviously insufficient. Therefore, biomimetic sensing technology is still in its infancy. Therefore, in addition to continuing to develop a new series of biomimetic sensors And improve the existing series, the biomembrane immobilization technology and solid-state biomimetic sensor deserved further study. In the near future, biomimetic sensors that simulate the functions of the organism will appear, which may exceed the sensitivity of human facial features and improve the robot's vision, taste, touch, and ability to operate on objects. We can see the broad prospects for biomimetic sensor applications, but these require the further development of biotechnology, and we'll see this day coming. V. Infrared SensorInfrared sensorInfrared technology has been developed to the present, as we all know. This technology has been widely used in modern science and technology, national defense and agriculture, and other fields. Infrared sensing systems are infrared-based measurement systems that can be divided into five categories based on function: (1) radiometers for radiation and spectroscopic measurements; (2) search and tracking systems for searching and tracking infrared targets, determining Its spatial position and its movement are tracked; (3) The thermal imaging system can produce a distribution image of the entire target infrared radiation; (4) Infrared ranging and communication systems; (5) Hybrid systems, refer to the above categories A combination of two or more in the system. Let us look at the composition of the infrared system, the main optical system, and auxiliary optical system, on the basis of which the key components of infrared are discussed in detail. In fact, the working principle of the infrared sensor is not complicated, the working principle of each part of a typical sensor system is as follows: (1)The target object. According to the infrared radiation characteristics of the target to be set, the infrared system can be set. (2)Atmospheric attenuation. When the target's infrared radiation passes through the Earth's atmosphere, the infrared radiation emitted by the infrared source will be attenuated due to the scattering and absorption of gas molecules and various gases, and various sol particles. (3) Optical receiver. It receives a portion of the target's infrared radiation and transmits it to the infrared sensor. Equivalent to a radar antenna, often used as an objective lens. (4) Radiation modulator. Radiation from the target under test is modulated into alternating radiant light to provide the target orientation information and to filter out large areas of interfering signals. Also known as a reticle and chopper, it has a variety of structures. (5) Infrared detector. This is the heart of the infrared system. It is the use of infrared radiation and the physical interaction between the physical effects of detecting infrared radiation sensors, in most cases is the use of this interaction presented by the electrical effects. Such detectors can be divided into two types of photon detectors and thermal detectors. (6) Detector cooler. Since some detectors must work at low temperatures, the corresponding system must have refrigeration equipment. After cooling, the equipment can shorten the response time and increase detection sensitivity. (7) Signal processing system. The detected signal is amplified, filtered, and extracted from these signals. This information is then converted into the required format and finally delivered to the control device or display. (8) Display device. This is the terminal device of the infrared device. Commonly used displays include oscilloscopes, kinescopes, infrared sensitized materials, indicating instruments, and recorders. Here gives a video of infrared sensors:Working principle of infrared sensorAccording to the above process, the infrared system can complete the measurement of the corresponding physical quantity. The infrared system is the core of infrared detectors, according to the detection mechanism of different, can be divided into two categories of heat detectors and photon detectors. The heat detector is used as an example to analyze the principle of the detector. The thermal detector is the use of radiant heat effect, so that the detection element causes the temperature to rise after receiving radiation, and thus makes the detector temperature-dependent performance changes. By detecting a change in one of these properties, radiation can be detected. In most cases, radiation is detected by thermoelectric changes. When the element receives the radiation and causes a non-electrical physical change, the corresponding change in the amount of electricity can be measured by appropriate transformation. Infrared sensors have played an important role in modern production practices. With the improvement of detection equipment and other parts of technology, infrared sensors can have more performance and better sensitivity. VI. Electromagnetic Sensor Magnetic sensors are the oldest sensors and compass is the earliest application of magnetic sensors. However, as a modern sensor, in order to facilitate the signal processing, a magnetic sensor is required to convert the magnetic signal into an electrical signal. The earliest applications were magnetoelectric sensors manufactured on the principle of electromagnetic induction. This magnetic sensor has made an outstanding contribution to industrial control. But today it has been replaced by a new type of magnetic sensor based mainly on high-performance magnetically sensitive materials.The shape of an electromagnetic sensorAmong the electromagnetic effect sensors used today, the magnetic rotation sensor is an important one. Magnetic rotation sensor mainly by the semiconductor magnetoresistive components, permanent magnets, fixtures, enclosures, and other components. A typical structure is a pair of magnetoresistive elements mounted on a permanent magnet stimulation, the input and output terminals connected to the fixture, and then installed in the metal box, and then sealed with plastic to form a closed structure, the structure has good reliability. Magnetic rotation sensor has many advantages of semiconductor magnetoresistance element. In addition to having high sensitivity and a large output signal, it also has a strong speed detection range, which is due to the development of electronic technology. In addition, this sensor can also be used in a wide temperature range, has a long working life, resistance to dust, water, and oil, and therefore withstand a variety of environmental conditions and external noise. Therefore, this kind of sensor has received widespread attention in industrial applications. Magnetic rotary sensors are widely used in factory automation systems because they have satisfactory characteristics and do not require maintenance. Its main application is the machine tool servo motor rotation detection, factory automation robotic arm positioning, hydraulic stroke detection, factory automation related equipment position detection, rotary encoder detection unit, and a variety of rotating detection unit. Modern magnetic rotation sensors mainly include four-phase sensors and single-phase sensors. In the course of work, four-phase differential rotation sensor with a pair of detection unit to achieve differential detection, the other to achieve the inverted differential detection. In this way, four-phase sensor detection capability is four times single-element. The two-element single-phase rotation sensor also has its own advantages, that is, small and reliable features, and the output signal can detect low-speed movement, anti-environmental impact, and anti-noise ability, low cost. Therefore, single-phase sensors will also have a good market. Magnetic rotary sensors also have great potential for use in household appliances. In the reversing mechanism of the cassette recorder, a magnetic resistance element can be used to detect the end of the magnetic tape. Most home video recorders have a variable speed and high-speed playback function, which can also be used magnetic spindle sensors to detect the spindle speed and control, to obtain a high picture quality. The positive and negative rotation of the motor in the washing machine and the high and low-speed rotation functions can be detected and controlled by the servo rotation sensor. Electromagnetic proximity switch. This switch can be sensed into the metal area of their own test objects, control their own internal circuit on or off. The switch generates its own magnetic field. When a metal object enters the magnetic field, it will cause a change in the magnetic field. This change can be turned into an electrical signal by switching the internal circuitry. The electromagnetic sensor is a widely used high-tech, both at home and abroad have invested some research efforts in research, the application of this sensor is penetrating into the national economy, national defense construction and people's daily life in all fields, with the information The arrival of society, its status and role will certainly be more prominent. VII. Magneto-optical Effect SensorMagneto-optical effect sensorModern electric measurement technology is maturing day by day, has the advantages of high precision, easy to real-time processing connected to a microcomputer, etc., has been widely used in the measurement of electrical and non-electrical measurements. However, the electrical measurement method is susceptible to interference. In the AC measurement, the frequency response is not wide enough and there are certain requirements on voltage and insulation. With the rapid development of laser technology, the above problems have been solved. Magneto-optic effect sensors are high-performance sensors using laser technology. Laser is another new technology that has been rapidly developed in the early 1960s. Its appearance signals that people have mastered and utilized light waves and entered a new stage. Due to the low monochromaticity of ordinary light sources in the past, many important applications are limited. The advent of lasers makes radio technology and optical technology by leaps and bounds, penetrate each other and complement each other. Today, many sensors have been fabricated using lasers that solve many of the unsolved technical problems that make them suitable for use in hazardous, flammable places such as coal, oil, and gas storage. For example, optical fiber sensors made of laser can measure the situation of crude oil injection, cracking oil tank parameters. It is not necessary to supply power at the place of measurement. This is particularly applicable to the petrochemical equipment group that requires strict safety and explosion protection measures. It can also be used to implement optical method telemetry chemistry in some aspects of large-scale steel plants. The principle of magneto-optic effect sensor mainly utilizes the polarization state of light to realize the function of the sensor. When a beam of polarized light passes through the medium, if there is an external magnetic field in the beam propagation direction, the light will rotate through the plane of polarization by an angle, which is the magneto-optical effect. That is, the applied magnetic field can be measured by the angle of rotation. Under certain experimental setups, the angle of deflection is proportional to the intensity of the output, and the laser diode LD is illuminated by the output light to obtain the digitized light intensity that is used to measure a particular physical quantity.Magneto-optical effect sensorSince the late 1960s, RC Lecraw has raised great concerns after his research report on magneto-optical effects was presented. Japan, the Soviet Union, and other countries have conducted research, and domestic scholars have also explored it. Magneto-optical sensor with excellent electrical insulation properties and anti-interference, wide frequency response, safety, and explosion-proof and other characteristics, and therefore for some special occasions electromagnetic parameters of measurement, has a unique effect, especially in the power system high voltage and current The measurement aspect shows its potential advantages. At the same time, by developing the software and hardware of the processing system, automatic real-time measurement of the welding machine and the robot control system can also be realized. In the use of magneto-optic effect sensors, the most important thing is to choose magneto-optical media and lasers. Different devices have different capabilities in terms of sensitivity and working range. With the advent of high-performance lasers and new types of magneto-optical media in recent decades, the performance of magneto-optical effect sensors has become stronger and the applications have become more widespread. Magneto-optical sensor, as a specific purpose sensor, can play its own function in a particular environment. It is also a very important industrial sensor. VIII. How to Choose Industrial SensorsModern sensors vary widely in principle and structure. How to select a sensor based on a specific measurement purpose, measurement object, and measurement environment is the first problem to be solved when performing a certain amount of measurement. When the sensor is determined, the matching measuring method and measuring equipment can be determined. The success or failure of measurement results depends to a large extent on the reasonableness of the choice of sensors. The influencing factors are: (1) Determine the type of the sensor according to the measurement object and the measurement environment. (2)Selection of the sensitivity. (3)Frequency response. (4) Linear range. (5)Stability.(6) Accuracy. FAQ 1. What sensor means?a device that responds to a physical stimulus (such as heat, light, sound, pressure, magnetism, or a particular motion) and transmits a resulting impulse (as for measurement or operating a control) .2. What is the purpose of a sensor?A sensor converts the physical action to be measured into an electrical equivalent and processes it so that the electrical signals can be easily sent and further processed. The sensor can output whether an object is present or not present (binary) or what measurement value has been reached (analog or digital). 3. How do sensors work?Put simply, a sensor converts stimuli such as heat, light, sound and motion into electrical signals. These signals are passed through an interface that converts them into a binary code and passes this on to a computer to be processed. 4. What can sensors detect?Broadly speaking, sensors are devices that detect and respond to changes in an environment. Inputs can come from a variety of sources such as light, temperature, motion and pressure. 5. What are the importance of sensors in our daily life?Intelligent sensor systems are omnipresent in our everyday lives. They provide security, save lives and improve our quality of life. As more and more areas of life are automated and networked, the importance of innovative sensor technologies will also increase in the future. 6. How do we classify sensors?Classification of Sensors:Active and Passive Sensors. Contact and Non-Contact Sensors.Absolute and Relative Sensors.Analog and Digital Sensors.Miscellaneous Sensors. 7. How are sensors used to collect data?With a sensor, a machine observes the environment and information can be collected. A sensor measures a physical quantity and converts it into a signal. Sensors translate measurements from the real world into data for the digital domain. 8. What is the difference between sensor and transducer?The main difference between sensor and transducer is that a transducer is a device that can convert energy from one form to another, whereas a sensor is a device that can detect a physical quantity and convert the data into an electrical signal. 9. Why do we need a temperature sensor?Within our homes, temperature sensors are used in many electrical appliances, from our refrigerators and freezers to help regulate and maintain cold temperatures as well as within stoves and ovens to ensure that they heat to the required levels for cooking, air confectioners/heaters. 10. How sensors are connected?A sensor device directly connected to a computer. A connected sensor is a sensor that also has a way to send data to either a local network or the Internet. Diagram of a sensor receiving waves on the left and broadcasting a wireless signal on the right to a router. A sensor device wirelessly connected to a network. 11. Can a transducer be a sensor?A Sensor is defined as a device which measures a physical quality (light, sound, space) and converts them into an easily readable format. If calibrated correctly, sensors are highly accurate devices. Not all transducers are sensors but most sensors are transducers. 12. What is the difference between active and passive sensors?Active sensors have its own source of light or illumination. In particular, it actively sends a pulse and measures the backscatter reflected to the sensor. But passive sensors measure reflected sunlight emitted from the sun. When the sun shines, passive sensors measure this energy. 13. What are the basic characteristics considered in the process of sensor selection?Sensor selection criteria include temperature, size, protection class, and whether the sensor requires a discrete or analog input. Also consider sensor repetition accuracy, sensor response speed, and sensing range. 14. What are the applications of sensors?Sensors are central to industrial applications being used for process control, monitoring, and safety. Sensors are also central to medicine being used for diagnostics, monitoring, critical care, and public health. 15. How do you check the accuracy of a sensor?To find out the accuracy of sensor you have to take several readings by your sensor on that particular one input parameter (like. temperature). after accumulating those sensor output values evaluate the standard deviation as per law, which indicate the accuracy level of your sensor. 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kynix On 2018-03-14
Light emitting diode (LED) is a light source that meets the requirements of green lighting. LEDs are safe, efficient, environmentally friendly, long-lived, responsive, small in size and robust in construction with many features that are unmatched by ordinary light-emitting devices. Moreover, it is one of the first semiconductor devices and is widely used. Currently, LEDs are widely used as indicators for various electronic products and as light sources for fiber optic communication. How dose a diode work? Catalog I What is a diode? II How dose a diode work? III What is diode characteristics? IV What are diode parameters? V What are the types of diodes? FAQ I What is a diode? Diode is an electronic device made of semiconductor materials (silicon, selenium, germanium, etc.) . It has a unidirectional conductivity, that is, the diode anode and cathode to add a forward voltage, the diode conducts. When the reverse voltage is added to the anode and cathode, the diode cuts off. Therefore, the on and off of the diode is equivalent to the on and off of the switch. In almost all electronic circuits, semiconductor diodes are used. The use of semiconductor diodes in the circuit can play a role in protecting the circuit, extending the life of the circuit. The development of semiconductor diodes has made integrated circuits more optimized and has played an active role in various fields. Diodes have many roles in integrated circuits and maintain the proper functioning of the integrated circuits. Diodes were one of the first semiconductor devices to be created, and their applications are very widespread. Especially in a variety of electronic circuits, the use of diodes and resistors, capacitors, inductors and other components to make a reasonable connection to form a circuit of different functions, you can achieve a variety of functions such as rectification of alternating current, detection of modulated signals, limiting and clamping, and voltage regulation of the supply voltage. Whether in common radio circuits or in other household appliances or industrial control circuits, diodes can be found. A diode is made of a PN junction with corresponding electrode leads and a tube housing package. The diode has two electrodes, the electrode leading from the P area is the positive electrode, also known as the anode; the electrode leading from the N area is the negative electrode, also known as the cathode. Diode structure There are many kinds of diodes: - According to the semiconductor materials used, they can be divided into germanium diodes and silicon diodes. - According to their different uses, they can be divided into detector diodes, rectifier diodes, zener diodes, switching diodes, etc. - According to the structure of the tube core, they can be divided into point-contact diodes, surface-contact diodes and planar diodes. -- The point contact diodes are pressed on the smooth surface of the semiconductor wafer with a thin metal wire. With pulse current, one end of the contact wire is sintered firmly with the wafer to form a "PN junction". Due to point contact, only small currents (no more than a few tens of mA) are allowed, which is suitable for high frequency low current circuits, such as radio detection, etc. The area of "PN junction" of surface contact diode is large, which allows large currents passing through and is mainly used in "rectifying" circuits that convert AC to DC. -- Planar diode is a kind of special silicon diode. It not only can pass through large current, but also has stable and reliable performance. It is widely used in switching, pulse and high frequency circuits. II How does a diode work? The crystal diode is a p-n junction formed by p-type semiconductor and n-type semiconductor. It forms a space charge layer on both sides of the interface and has a self-built electric field. When there is no applied voltage, the diffusion current caused by the carrier concentration difference on both sides of the p-n junction is equal to the drift current caused by the self-built electric field, so it is in an electric equilibrium state. When the external positive voltage is biased, the mutual suppression of the external electric field and the self-built electric field results in the increase of the carrier diffusion current, which is shown in the conduction region below. When the external reverse voltage is biased, the external electric field and the self-built electric field are further strengthened to form a reverse saturation current I0 independent of the reverse bias voltage value within a certain reverse voltage range, which is shown in the cut-off region below. When the applied reverse voltage is high enough to a certain extent, the electric field intensity in the space charge layer of p-n junction reaches the critical value to produce the multiplying process of the carriers, resulting in a large number of electron hole pairs and a numerical reverse breakdown current is generated, known as the diode breakdown, which is shown in the breakdown region below. III What is diode characteristics? The most important characteristic of the diode is the unidirectional conductivity. In the circuit, the current can only flow from the positive electrode of the diode, and flows out from the negative electrode . The forward and reverse characteristics of the diode are illustrated by simple experiments. 3.1 Forward characteristics In electronic circuits, if the diode is connected to the high potential terminal and the negative electrode to the low potential terminal, the diode will be switched on. This connection is called forward bias. It must be noted that when the forward voltage applied to both ends of the diode is very small, the diode still cannot be switched on, and the forward current flowing through the diode is very weak. Only when the forward voltage reaches a certain value (about 0.6 V of the silicon tube) can the diode be truly switched on. The voltage at both ends of the diode after conduction is called the forward voltage drop of the diode. 3.2 Reverse characteristic In the electronic circuit, the positive end of the diode is connected to the low potential end, the negative electrode is connected to the high potential terminal, and the diode is in the cutoff state. This mode of connection is called reverse bias. When the diode is in reverse bias, there will still be a weak reverse current flowing through the diode, called leakage current. When the reverse voltage of the diode increases to a certain value, the reverse current will increase sharply, and the diode will lose the single direction conduction characteristic. This state is called the breakdown of diode. IV What are diode parameters? The technical specifications used to test the performance of diodes are called diode parameters. Here are some of the main parameters in diode testing: 4.1 Rated forward working current (IF) Refers to the maximum forward current that is allowed to pass through the diode when it is in continuous operation over a long period of time. When a larger current passes through the diode, the dice is heated and the temperature rises, and when the temperature exceeds the allowable limit, the dice is overheated and damaged. Therefore, it should not exceed the diode rated forward operating current value when the diode is in use. Eg. The rated forward working current of DFM is 1A 4.2 Forward Voltage(VF) Refers to the voltage at both ends of the diode when the rated forward working current IF is passed through the diode. Eg. The voltage at both ends of the diode is about 0.9V when the forward working current of DFM is 1A. 4.3 Maximum reverse operating voltage (VR) When the reverse voltage at both ends of the diode is raised to a certain value, the diode will be broken down and the unidirectional conductivity will be lost. In order to ensure the safety of operation, the maximum reverse operating voltage is specified. Eg. The maximum reverse operating voltage of DF10M is 1100V and the breakdown voltage is about 1400V 4.4 Reverse current IR Refers to the reverse current that flows through the diode when the maximum reverse operating voltage VR is applied to both ends of the diode. The smaller the reverse current, the better the unidirectional conductivity of the diode will be. Eg. When the reverse voltage of DF10M is 1100V, the VR is about 0.2uA. 4.5 Reverse critical current (IZ) Refers to the reverse current of the diode increases sharply to close to the breakdown phenomenon. Eg. Set the IZ of DF10M to 0.1 Ma (Ma) 4.6 Reverse critical voltage (VZ) Refers to the reverse voltage of the diode when the reverse current is IZ. If the reverse voltage is greater than this value, the reverse current increases dramatically and the unidirectional conductivity of the diode is destroyed, thus causing reverse breakdown. Eg. The VZ is about 1300V when IZ of DF10M is 0.1mA. 4.7 Reverse recovery time (Trr) When diodes are in low frequency applications, it generally do not need to consider its conduction to the cut-off, or cut-off to the transition time. But if the diode works in a high-speed switching circuit environment, when diode suddenly turns to reverse bias from the forward biased conduction state, it will take a certain time to become a cut-off state, which is called reverse recovery time. But if the diode works in a high-speed switching circuit environment, when diode suddenly turns to reverse bias from the forward biased conduction state, it will take a certain time to become a cut-off state, which is called reverse recovery time. Eg. The maximum Trr of EDF1DM is 50nS. V What are the types of diodes? 5.1 Light emitting diode Light emitting diode, also called LED, is a semiconductor diode that converts electrical energy into luminous energy. Like ordinary diodes, LEDs are made up of a PN junction and have unidirectional conductivity. When a forward voltage is applied to a light-emitting diode, Holes injected from P region to N region and electrons injected from N region to P region are recombined with N region electrons and P region holes in several microns near PN junction to produce spontaneous emission fluorescence. The energy states of electrons and holes in different semiconductor materials are different. When electrons and holes are combined, the energy released is different. The more energy is released, the shorter the wavelength of light is. The commonly used diodes are red, green or yellow light.The reverse breakdown voltage of a light-emitting diode is greater than 5 volts. Its forward volt-ampere characteristic curve is so steep that it must be used in series to control the current passing through the diode. The current limiting resistance R can be calculated by the following formula: R=(E-UF)/IF . In this formula, E is the power supply voltage, UF is the forward voltage of LED, IF is the running current of LED. 5.2 Zener diode Zener diode, is also called voltage stabilizing diode. By using the reverse breakdown state of pn junction, the current can be changed in a wide range and the voltage is basically unchanged, thus form a diode which has voltage stabilizing function. This diode is a semiconductor device with high resistance until it reaches the critical reverse breakdown voltage. The following picture is a typical Zener diode application circuit diagram: At this critical breakdown point, the reverse resistance is reduced to a very small value, where the current increases and the voltage remains constant in this low resistance region, and the Zener diode is divided according to the breakdown voltage, because of this characteristic, The regulator is mainly used as a voltage regulator or voltage reference element. Zener diodes can be connected in series for use at higher voltages, and higher stable voltages can be obtained by serializing them. 5.3 Switching diode Working principle: The semiconductor diode is equivalent to switch-on when it is turned on (the circuit is turned on), and is equivalent to switch-off when it is turn-off (the circuit is cut off), so the diode can be used as a switch. The common used model is 1N4148. Due to the unidirectional conductivity of semiconductor diodes, the PN junction is on at positive bias, and the resistance is very small at the on-state, which ranges from tens to hundreds of ohs. At reverse bias, it is in a cut-off state, and its resistance is very large. Generally, silicon diodes are above 10 μ Ω and germanium diodes have tens to hundreds of kilos. By using this property, the diode will play the role of controlling the current on or off in the circuit and become an ideal electronic switch. At high frequency, the barrier capacitance of the diode exhibits extremely low impedance and is parallel to the diode. When the capacitance of the barrier itself reaches a certain level, the switching performance of the diode will be seriously affected. In extreme conditions, the diode will be short-circuited, and the high-frequency current will no longer pass through the diode, but will pass directly through the barrier capacitance, and the diode will fail to work. The barrier capacitance of the switching diode is generally small, which is equivalent to blocking the barrier capacitance path and achieving the effect of maintaining good unidirectional conductivity at high frequency. Classification: General switching diode, high speed switching diodes, ultra-high speed switching diodes, low-power switching diodes, high reverse voltage switching diodes, silicon voltage switching diodes and so on. 5.4 Variable capacitance diode( Varactor Diodes ) Variable capacitance diode, also known as varactor Diodes, are semiconductors that change the junction capacitance according to the voltage supplied. That is, as variable capacitors, they can be used in resonant circuits such as FM tuners and TV tuners and FM modulation circuits. Working principle: Varactor Diodes is a kind of special diode. When applied forward bias voltage, the depletion region of PN (positive and negative electrode) junction is narrowed and the capacitance becomes larger, which results in diffusive capacitance effect. However, the leakage current will be generated when the forward bias is added, so the reverse bias is supplied in application. In fact, we can think of it as a PN junction. If a reverse voltage V is added to the PN junction (the varactor diode is used in reverse direction), the electrons in the N-type semiconductor are directed to the positive electrode and holes in P-type semiconductor will be led to the negative electrode. Then forms a depletion layer that has neither electrons nor holes, and the width of the depletion layer is set to d, which changes with the reverse voltage V. In this way, when the reverse voltage V increases, the depletion layer d becomes wider and the diode capacitance C decreases (according to C=kS/d), and the reverse voltage decreases, the depletion layer width d becomes narrower and the diode capacity becomes larger. The change of reverse voltage V leads to the change of depletion layer, which changes the junction capacity of the variable capacitance diode. - Application: the varactor diode is a semiconductor device based on the principle of variable capacitance between PN junctions. It is used as a variable capacitor in high frequency tuning and communication circuits. As shown in the following figure, the reverse voltage of the diode is changed by changing the different R2. This will result in a change in the capacitance of the diode, thus changing the resonant frequency in which the varactor diode can pull out the full range of the required capacitance in the parallel resonant band-pass filter. FAQ 1. What is diode and its symbol? Diode, an electrical component that allows the flow of current in only one direction. In circuit diagrams, a diode is represented by a triangle with a line across one vertex. 2. What is special about a diode? Some semiconductor junctions, composed of special chemical combinations, emit radiant energy within the spectrum of visible light as the electrons change energy levels. Simply put, these junctions glow when forward biased. A diode intentionally designed to glow like a lamp is called a light-emitting diode, or LED. 3. Are diodes AC or DC? It allows current to flow easily in one direction, but severely restricts current from flowing in the opposite direction. Diodes are also known as rectifiers because they change alternating current (ac) into pulsating direct current (dc). Diodes are rated according to their type, voltage, and current capacity. 4. Why do we use zener diode? Zener diodes are used for voltage regulation, as reference elements, surge suppressors, and in switching applications and clipper circuits. The load voltage equals breakdown voltage VZ of the diode. The series resistor limits the current through the diode and drops the excess voltage when the diode is conducting. 5. What is unit of diode? A diode is not a measurable quantity. Hence,it does not have a unit. Generally,for a diode,we measure characteristics like forward voltage drop,reverse voltage drop and reverse breakdown voltage which are usually measured in Volts. 6. Do diodes have resistance? Just like a resistor or any other load in a circuit, a diode offers resistance in a circuit. Unlike resistors, though, diodes are not linear devices. This means that the resistance of diodes does not vary directly and proportional to the amount of voltage and current applied to them. 7. Does diode reduce current? Ideally, diodes will block any and all current flowing the reverse direction, or just act like a short-circuit if current flow is forward. Unfortunately, actual diode behavior isn't quite ideal. Diodes do consume some amount of power when conducting forward current, and they won't block out all reverse current. 8. How are diodes classified? Diodes are classified according to their characteristics and are offered in a number of different types, including rectifiers, switching diodes, Schottky barrier diodes, Zener (constant voltage) diodes, and diodes designed for high-frequency applications. 9. What is the most common diode? The most commonly used signal diode is the 1N4148. This diode has a close brother called 1N914 that can be used in its place if you can't find a 1N4148. This diode has a forward-voltage drop of 0.7 and a peak inverse voltage of 100 V, and can carry a maximum of 200 mA of current. 10. What is the difference between a Zener diode and a Schottky diode? As their switching speed is very high, Schottky diodes recover very fast when the current reverses, resulting in only a very small reverse current overshoot. ... A special type of diode, called the Zener diode, blocks the current through it up to a certain voltage when reverse biased. 11. What is difference between Schottky diode and normal diode? In the normal rectifier grade PN junction diode, the junction is formed between P type semiconductor to N type semiconductor. Whereas in Schottky diode the junction is in between N type semiconductor to Metal plate. The schottky barrier diode has electrons as majority carriers on both sides of the junction. 12. Why it is called diode? A diode is called a diode because it has two distinct electrodes (i.e. terminals), called the anode and the cathode. A diode is electrically asymmetric because current can flow freely from the anode to the cathode, but not in the other direction. In this way, it functions as a one-way valve for current. 13. Is a diode the same as a resistor? Key Difference: A diode is a type of electrical device that allows the current to move through it in only one direction. ... A resistor is an electric component that is used to provide resistance to current in the circuit. They are mostly used to produce heat or light. 14. How much voltage can a diode take? Silicon diodes have a forward voltage of approximately 0.7 volts. Germanium diodes have a forward voltage of approximately 0.3 volts. The maximum reverse-bias voltage that a diode can withstand without “breaking down” is called the Peak Inverse Voltage, or PIV rating. 15. Can a resistor replace a diode? Diodes only conduct in one direction whereas resistors conduct in both directions. Without analyzing the actual circuit the results would be unpredictable but, generally speaking, being that diodes & resistors are designed to do different things, substituting one for the other is something you wouldn't want to do.
kynix On 2018-03-12
Warm hints: The word in this article is about 2500 and reading time is about 12 minutes. The fiber optic sensor consists of the light source, incident fiber, exit fiber, light modulator, light detector, and demodulator. The basic principle is that the light of the light source is sent to the modulation area through the incident optical fiber, and the light interacts with the measured parameters in the modulation area to change the optical property of the light into the modulated signal light which is then sent through the outgoing fiber optical detector, demodulator and get the measured parameters. In recent years, sensors have evolved in the direction of sensitivity, precision, adaptability, compactness, and intelligence. Optical fiber has many excellent properties, such as anti-electromagnetic interference and atomic radiation performance, soft and lightweight mechanical properties. Insulation, non-responsive electrical properties. Water, heat, and corrosion resistance of chemical properties, can reach people's eyes and ears in unattainable places (such as high-temperature areas), or in areas harmful to humans (such as nuclear radiation area), but also can transcend human physiological boundaries and receive sensory organs Unexpected outside information. Catalogs I. Basic Structure and Principle of Fiber Optic SensorII. Application of Light Sensor in Petrochemical Industry2.1 The application of fiber optic sensor in the petrochemical system2.2 The application of fiber optic sensor in oil loggingIII. Application of Fiber Optic Sensors in Power Systems3.1 Applications in the high voltage cable temperature and strain measurement3.2 Application in Electric Power Sensors3.3 Application of optical fiber cable monitoringIV. Fiber Optic Sensors in Medical Applications4.1 Pressure measurement4.2 Blood flow velocity measurement4.3 PH measurementV. Fiber Optic Sensor FeaturesFAQ I. Basic Structure and Principle of Fiber Optic Sensor The fiber optic sensor consists of the light source, incident fiber, exit fiber, light modulator, light detector, and demodulator. The basic principle is that the light of the light source is sent to the modulation area via the incident fiber, and the light interacts with the measured parameters in the modulation area to make the optical properties (such as intensity, wavelength, frequency, phase, and normality) of the light occur Changes into a modulated signal light, and then sent through the optical fiber into the optical detector, demodulator to obtain the measured parameters. Fiber optic sensors can be divided into two categories by sensing principle: one is the light transmission (non-functional type) sensor, the other is the sensor type (functional) sensor. In the fiber optic sensor, the optical fiber only as a light transmission medium, the measured signal is detected by other sensitive components, this exit fiber, and the incident optical fiber is not continuous. Between the two Modulators are spectrally sensitive or other types of sensitive elements. In the sensing type fiber optic sensor, the optical fiber has both the sensitivity to the signal to be measured and the transmission of the optical signal. And the "sense" and "pass" of the signal are combined so that the optical fiber in such a sensor is continuous. Due to the different roles played by the optical fibers in these two sensors, the requirements for the optical fibers are also different. Optical fiber in the light-transmitting sensor only plays the role of light transmission. The use of communication fiber even ordinary multi-mode fiber can meet the requirements, and sensitive components can be a very flexible selection of high-quality materials. So the sensitivity of these sensors needs more optical coupling devices, the structure is more complex. The structure of sensing type fiber optic sensor is relatively simple with fewer coupling devices, but higher requirements on the optical fiber. It often needs to be sensitive to signal measurement, with good transmission characteristics. So far, most people adopt the former, but with the improvement of optical fiber manufacturing technology, sensor-type fiber optic sensors will also be widely used. According to the principle of light being modulated in optical fiber, fiber optic sensors can be divided into intensity modulation, phase modulation, polarization modulation, frequency modulation, wavelength modulation, and so on. Up to now, optical sensors have been able to measure more than 70 physical quantities. Fiber Optic Sensors have unique advantages over traditional sensors. (1) High sensitivity. Since light is a very short wavelength electromagnetic wave, its optical length is obtained by the phase of light. Taking an optical fiber interferometer as an example, due to the small diameter of the fiber used, its optical length is subject to slight mechanical external force or temperature change, causing a large phase change. Suppose that with a 10-meter optical fiber, a change of 1 ° C causes a phase change of 1000ard. If the minimum phase change that can be detected is 0.01ard, the minimum change in temperature that can be measured is 10 ° C, showing a high sensitivity. (2) Anti-electromagnetic interference, electrical insulation, corrosion resistance, intrinsically safe. Since fiber optic sensors transmit information using light waves, optical fibers are an electrically insulating, corrosion-resistant transmission medium and safe, which makes it easy and effective to use All kinds of large electromechanical, petrochemical, mine and other strong electromagnetic interference and flammable and explosive and other harsh environments. (3) Fast measurement. Light travels fastest and can transmit two-dimensional information, so it can be used for high-speed measurements. The analysis of radar and other signals requires an extremely high detection rate. The application of electronics is difficult to achieve. Using high-speed spectral analysis of light diffraction can be solved. (4) Large information capacity. The signal under test is a light wave carrier, and the light has a very high frequency. The contained frequency band is very wide. The same optical fiber can transmit multiple signals. (5) Suitable for harsh environments. Optical fiber is a dielectric, high voltage, corrosion-resistant, anti-electromagnetic interference that can be used for other sensors that do not adapt to the harsh environment. In addition, fiber-optic sensors are also characterized by their lightweight, small size, flexibility, wide measurement range, good reusability, and low cost. The application of fiber optic sensors is precise because fiber optic sensors have so many advantages, making it a very wide range of applications, involving petrochemicals, power, medicine, civil engineering, and many other fields. Video 1 Introduction of fiber optic sensorsII. Application of Light Sensor in Petrochemical Industry 2.1 The application of fiber optic sensor in the petrochemical systemIn the petrochemical system, due to the underground environment with high temperature, high pressure, chemical corrosion and electromagnetic interference, and other characteristics, the conventional sensor is difficult to play a role in the well. However, the fiber itself is no charge, small and light, easy to bend, anti-electromagnetic interference, and anti-radiation performance. Particularly it is suitable for flammable and explosive, strict restrictions and strong electromagnetic interference, and other harsh environments. Fiber optic sensors in the measurement of the good parameters play an irreplaceable role. It will become the oil and gas exploration and oil logging and other logging A field of broad market prospects of new technologies. Fiber optic sensor application in oil and gas exploration. Because of its high-temperature capability, multi-communications, distributed sensing capabilities, and the fact that it requires only a small space to meet its use conditions, fiber optic sensors make it particularly unique in exploration drilling. The application of fiber optic sensors can be made into the downhole spectrometer, distributed temperature sensor, and optical fiber pressure sensor, and other products suitable for this special job requirement. (1) The downhole spectrometer fluid analyzer shown in Figure 1 can be used to understand the crude oil composition during the initial development process. It consists of two sensors: one is the absorption spectroscopy fiber and the other is the fluorescence and gas detector. Downhole fluid is introduced into the tubing by formation probes and the optical sensor is used to analyze the fluid within the tubing. Fluid analysis spectrometers provide in-situ downhole fluid analysis and improve formation fluid evaluation. (2) Distributed temperature sensors. Optical fiber distributed temperature sensors are the most popular fiber optic sensors for downhole applications. The application example is to monitor the steam injection heavy oil recovery system. Steam is injected into the heavy oil reservoir to reduce the viscosity of the oil, allowing heavy oil to be mined out. Downhole steam temperature can be as high as 250 ℃. Figure 1 Fluid analyzer structure(3) The fiber-optic pressure sensor is currently under development. Its main focus is on ultra-high temperature and downhole pressure monitoring tasks. Other commercial products based on fiber optic sensors are currently available. For example, fiber optic probes for multiphase flow measurements and distributed dynamic strain measurements. Its high reliability, high efficiency, and low power consumption are key factors in the success of optical fiber products in oil field applications. 2.2 The application of fiber optic sensor in oil loggingOil logging is one of the most basic and key aspects of the petroleum industry. The parameters such as pressure, temperature, and flow rate are important physical quantities in oil and gas wells. These advanced technologies are used for long-term Real-time monitoring, timely access to the information of oil and gas wells, the oil industry has a very important significance. Fiber optic sensors are insensitive to electromagnetic interference and withstand extreme conditions, including high temperatures and pressures, as well as strong shock and vibration, to measure borehole and well site environmental parameters with high accuracy, and have distributed measurement capabilities for fiber optic sensors. The spatial distribution gives the profile information. Moreover, the fiber optic sensor cross-sectional area is small, short in shape, in the wellbore occupies a very small space. Traditional electronic sensors do not have such features in the harsh underground environment. Fiber optic sensors can do downhole flow measurement, temperature measurement, pressure measurement, water (gas) measurement, density measurement, acoustic measurement. (1) Flow measurement. Because the intensity, phase, frequency, wavelength, and other characteristics of light in the optical fiber transmission process will be subject to flow modulation. A certain light detection method can convert the modulation into electrical signals, you can find the fluid flow, which is the fiber flow the working principle of the meter. (2) Temperature and pressure measurement. The distributed optical fiber measurement system (DTS) utilizes the Raman effect of the optical fiber to enable real-time monitoring of the temperature field where the fiber is located. The EFPI type (non-intrinsic FP interference) and FBG fiber optic sensors are wavelength-coded sensors. With high sensitivity, it also can simultaneously measure pressure, temperature, stress, and other parameters of the characteristics. The optical fiber thermal color temperature sensor is a reflective temperature sensor composed of a white light source and a multi-mode optical fiber. The optical fiber radiation temperature sensor utilizes black body radiation energy. Its non-contact, measurable instantaneous temperature, fast response, and no need for heat balance time are available. In high-temperature measurement, the semiconductor absorption-type optical fiber temperature sensor utilizes the characteristic that the absorption edge wavelength of its semiconductor material shifts to a longer wavelength as the temperature increases, and an appropriate semiconductor light-emitting diode is selected so that its spectral range falls exactly on the absorption edge region. , So the light intensity through the semiconductor decreases with increasing temperature. (3)Water (Gas) Rate and transmission power of U-shaped fiber used for density measurement vary with the refractive index of the external medium. The lightwave serves as an information carrier and has nothing to do with the resistivity, flow pattern, and water quality of the mixed fluid. The fiber holding rate is based on this principle. The density sensor essentially solves the problem of the application of high water content without resolution and radioactive substances in the existing holding ratios. For the multi-phase fluids, the refractive indices of oil, water, and gas are all different, so the refractive index of the mixed fluid will follow. Change the ratio of oil, water, gas changes. Therefore, this refractive index modulation type fiber optic sensor can not only measure the fluid holding rate, fluid density can be measured at the same time, for its accuracy is higher. (4) Sonic measurement. Seismic waves propagate in different media and the waveforms of the received seismic waves will be different. According to different seismic waveforms, the sedimentary sequence and sedimentary structure can be identified to locate the reservoir, determine the gutter, detect the damage and fracture of the casing, and perforation, detect layers and determine the fluid flow, and so on. VSP seismic logging means that the geophone is placed in a well and the seismic signal is received by the geophone in the well by means of a micro-vibration generated by ground-derived seismic waves or fluid flow in the well. The permanent downhole optical fiber three-component seismic survey has high sensitivity and directionality can produce high-precision spatial images. It can not only provide near-borehole images but also can provide strata images around the wellbore. And the measurement range can reach thousands of kilometers. It withstands harsh environmental conditions and has no moving parts and downhole electronics that can withstand strong shocks and vibrations and Can be installed in an extremely small space for complex completion string. III. Application of Fiber Optic Sensors in Power Systems Because of the complicated structure and wide distribution of power system networks, various hidden dangers exist on the high-voltage power line and power communication network. Therefore, it is very important for distributed monitoring of various lines and networks in the system. 3.1 Applications in the high voltage cable temperature and strain measurementAt present, foreign countries (mainly Britain, Japan, etc.) have developed the distributed optical fiber temperature sensor products by utilizing the laser Raman spectroscopy effect. And domestically, we are actively carrying out research work in this area. The domestic begin to introduce the distributed optical fiber temperature sensing technology into the power system cable temperature measurement. In connection with the snow disasters suffered in southern China last year, we can consider that if we can lay sensor fiber optic cables in parallel on high-voltage cables and measure the temperature, pressure, and other parameters of power system cables and towers in real-time, we can make timely measurements, so as to minimize economic losses. Fiber optic sensors in the power system will have a wide range of applications. Ideally, the fiber should be placed as close as possible to the cable core to more accurately measure the actual cable temperature. For direct-buried power cables, although the surface-mount fiber can not accurately reflect the change of cable load, it is more sensitive to the change of thermal resistivity of soil in the buried cable and can reduce the installation cost of optical fiber. 3.2 Application in electric power sensorsElectric power is the basic power reflecting the energy conversion and transmission in the power system. Electric power measurement is an important part of power metering. With the rapid development of the power industry, traditional electromagnetic measurement methods have increasingly exposed their inherent limitations, such as electrical insulation, electromagnetic interference, and magnetic saturation. Therefore, people have been working hard to find new methods for measuring electrical power. It can be said that the advent of fiber optic sensors has brought people the gospel to solve this problem. The main characteristics of fiber-optic power sensors are: Since electric power sensing involves both voltage and current at the same time, it is usually necessary to consider both electro-optic and magneto-optic effects. At the same time, two kinds of sensing media or one multifunctional media are used as sensitive elements. The structure of the fiber electric power sensor head is relatively complicated; the optical sensor signal of the fiber electric power sensor sometimes includes voltage and current signals at the same time, so the signal detection and processing methods thereof will also be more complicated. 3.3 Application of optical fiber cable monitoringIn Power Systems The power system has a wide variety of optical cables. In addition, China has a vast area and the environment varies widely. Therefore, the environment of optical cables is also very complex. Temperature and stress are the main environmental factors that affect the performance of optical cables. Therefore, while monitoring the breakpoint of the optical fiber, the temperature and stress conditions of the optical cable are also monitored. It can be seen that the optical fiber cable has far-reaching fault warning and maintenance. By measuring the frequency shift and intensity of the Brillouin scattered light along the length of the optical fiber, the temperature and strain information of the optical fiber can be obtained, and the sensing distance is relatively long, so it has far-reaching engineering research value. Based on Brillouin Optical Time Domain Reflectance (BOTDR) distributed optical fiber sensing system, using coherent detection technology, the system principle shown in Figure 2. Figure 2 based on BOTDR sensing system principleThe BOTDR fiber sensing system measures the self-distribution of scattering signals of an optical fiber and its signal strength is very weak, but the coherent detection technology can be used to improve the signal-noise ratio of the system. This solution can be a single light source, single-ended work, the system is simple and easy to implement, and can simultaneously detect fiber breakpoints, loss, temperature, and strain. IV. Fiber Optic Sensors in Medical Applications In medical fiber, sensors are mainly light-transmitting. With its small size, insulation, non-radio frequency, and microwave interference, high measurement accuracy and good affinity with living organisms, and other advantages. This article will mainly introduce the application of transmission optical fiber in pressure measurement, blood flow velocity measurement, and pH measurement. In addition, it can also be applied to the measurement of temperature and medical image transmission. 4.1 Pressure measurementCurrent clinically applied pressure sensors are mainly used to measure intravascular blood pressure, intracranial pressure, intracardiac pressure, bladder, and urethral pressure. The pressure sensor used to measure blood pressure is schematically shown in Figure3. The pressure-sensitive part is a water-repellent film on the sidewall of the tip of the probe catheter connected to the membrane by a cantilever micromirror and an optical fiber opposite the reflector for transmitting incident light to the reflector while The reflected light is also transmitted. When there is pressure on the film, the film is deformed and can drive the cantilever to change the angle of the mirror. The light beam coming from the fiber is shone on the mirror and then reflected at the end of the fiber. Since the direction of the reflected light changes with the angle of the mirror, the intensity of the reflected light received by the optical fiber also varies. This change passes through the optical fiber to the other end of the photodetector into an electrical signal, so that by changing the voltage to know the size of the probe at the pressure.Figure 3 Optical fiber pressure gauge probe 4.2 Blood flow velocity measurement Doppler-type optical fiber speed sensor measurement of subcutaneous tissue flow velocity shown in Figure 4, this device uses the optical fiber end reflection phenomenon, the measurement system is simple in structure.Figure 4 optical fiber pressure gauge probeLaser light with a frequency of f passes through the lens and the fiber is sent to the epidermal tissue. For immobile tissue, such as the vessel wall, the reflected light does not produce a frequency shift; and for the red blood cells in the cortex capillary flow rate, the reflected light to produce a frequency shift, the frequency change △ f. The frequency shift of the reflected light The intensity is proportional to the concentration of erythrocytes and the change in frequency can be proportional to the velocity of erythrocytes. Emitted light collected by the optical fiber, the first on the light detector for mixing, and then into the signal processing instrument, which get the red blood cell velocity and concentration. 4.3 PH measurementA schematic diagram of the pH fiber optic sensor used to determine tissue and blood values is shown in Figure 4. Its working principle is the use of emission light, the intensity of transmitted light with the wavelength distribution of the spectrum to be measured. The sensor inserts two optical fibers into an ion-permeable cellulose capsule containing reagent, which penetrates the reagent when the needle is inserted into the tissue or blood vessel, causing the reagent to absorb light of a certain wavelength. Measured such changes, you can get the blood or tissue pH.Figure 5 Determination of pH fiber spectrometerV. Fiber Optic Sensor Features 1.High sensitivity. 2.The geometry has a wide range of adaptability, can be made into any shape of the fiber optic sensor. 3.You can create sensors sensing a variety of different physical information (sound, magnetic, temperature, rotation, etc.) of the device. 4.Can be used for high voltage, electrical noise, high temperature, corrosion, or other harsh environments. 5.But also with the inherent compatibility of optical telemetry technology. The advantages of fiber-optic sensors are that optical fiber sensors use light as a carrier for sensitive information, and use optical fibers as a medium for transmitting sensitive information. Compared with conventional sensors. They have the characteristics of optical fiber and optical measurement and have a series of unique advantages. Good electrical insulation, anti-electromagnetic interference, non-invasive, high sensitivity, easy to achieve long-distance monitoring of the signal under test, corrosion resistance, explosion-proof, flexible optical path, easy to connect with the computer. Sensors are developed in the direction of sensitivity, precision, adaptability, compactness, and intelligence. They can serve as human eyes and ears where people cannot reach(such as high-temperature areas, are as harmful to humans, or nuclear radiation areas). But it is also beyond the physical boundaries of human beings, outsiders can not feel the sensory information. FAQ 1. How does a fiber optic sensor work?Fiber optic sensors work based on the principle that light from a laser or any superluminescent source is transmitted via an optical fiber, experiences changes in its parameters either in the optical fiber or fiber Bragg gratings and reaches a detector which measures these changes. 2. What are fiber optic sensors used for?Optical fibers can be used as sensors to measure strain, temperature, pressure and other quantities by modifying a fiber so that the quantity to be measured modulates the intensity, phase, polarization, wavelength or transit time of light in the fiber. 3.How are fiber optic sensors classified?Based on the operating principle or modulation and demodulation process, a optical fiber sensor can be classified as intensity, a phase, a frequency, or a polarization sensor. All these parameters may be subject to change due to external perturbations. ... These sensors are widely used as chemical sensors. 4. What is active and passive optical fiber sensor?Active fibre optic. -In optical fiber communication, because the signal usually decades during long distance transformation, you need to add an amplifier to boost the signal. Passive fibre optic. - Simply receive light data from the environment, it is commonly used for illumination (Fiber optical lighting. 5. What are the characteristics of optical fiber sensors?Optical fiber sensors have unique advantages, such as high sensitivity, immunity to electromagnetic interference, small size, light weight, robustness, flexibility, and the ability to provide multiplexed or distributed sensing. 6. Which is a use of fiber optics?They are widely used in lighting, both in the interior and exterior of vehicles. Because of its ability to conserve space and provide superior lighting, fiber optics is used in more vehicles every day. Also, fiber optic cables can transmit signals between different parts of the vehicle at very fast speed. 7. Why optical fiber is used for communication?Optical fiber is used by telecommunications companies to transmit telephone signals, Internet communication and cable television signals. ... Due to lower attenuation and interference, optical fiber has advantages over copper wire in long-distance, high-bandwidth applications. 8. Is fiber optic WIFI?Like any Internet service, fiber optic Internet download speeds depend on your connection. Not all fiber services are created equal, much like broadband. ... You can download more, faster, with fiber. Fiber Internet is more reliable than copper and less 'patchy' than Wifi. 9. Is fiber optic analog or digital?Digital signals can be transmitted long distances without degradation as the signal is less sensitive to noise. Fiber optic datalinks can be either analog or digital in nature, although most are digital. Both have some common critical parameters and some major differences. 10. How much data can a fiber optic cable transmit?A new fiber-optic system can carry 800 gigabits of data per second, a big step up from top speeds of 100 or 200 gigabits in today's data centers. You May Also Like:GPS and inertial sensors for driverless applicationsA New Technology for Advancing Opticals,Sensors Even Resistant SupercapacitorsSensors are Always In a State of Rapid Progress
kynix On 2018-03-09
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