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I IntroductionLaser sensor is a kind of sensor which uses laser technology to measure. It is generally composed of laser, optical parts and photoelectric devices. It can convert the measured physical parameters (such as length, flow, speed, etc.) into optical signals, and then use photoelectric converter to convert the optical signals into electrical signals. Through the filtering, amplification and rectification of corresponding circuits, the output signals can be obtained, so as to calculate the measured quantity. Laser technology has the characteristics of strong direction, high brightness and good monochromaticity. It is widely used in industrial and agricultural production, national defense and military, medical and health, scientific research and other aspects, such as distance measurement, precision detection, positioning, etc., as well as length benchmark and optical frequency benchmark.Laser Distance Sensor OverviewCatalogI IntroductionII What is Laser? 2.1 The Concept of Laser 2.2 Important Characteristics of Laser 2.3 Types of Laser 2.4 What can Laser Sensor Detect?III Laser Displacement Sensor 3.1 What is Laser Displacement Sensor 3.2 How Does Laser Displacement Sensor Work? 3.3 Application of Laser Displacement Sensor 3.4 What are the Parameters to Know When Choosing a Laser Displacement Sensor?IV Laser Distance Sensor 4.1 Classification of Laser Distance Sensors  4.2 Measuring Principle of Different Laser Distance Sensors 4.3 Application of Laser Distance SensorV Laser Sensor Application CaseVI FAQII What is Laser?2.1 The Concept of LaserLaser light is different from ordinary light. (See more about light and photoelectric effect in the article introducing light sensor and photoresistor)We need to use laser to produce laser light. In the normal state, most of the atoms in the laser are in stable low energy level E1. Under the action of appropriate frequency of external light, the atoms in low energy level absorb photon energy to excite and transition to high energy level E2. The photon energy E = e2-e1 = h V, where h is the Planck constant and V is the photon frequency.  On the contrary, when the frequency of light is V, the atom in level E2 will jump to the low energy level to release energy and emit light, which is called stimulated radiation. First of all, the laser makes the atoms of the working materials abnormally in the high-energy level (i.e. inversion distribution of the particle number ), which can make the stimulated radiation process dominant, so that the induced light with the frequency of V can be enhanced, and the large stimulated radiation light can be produced through the avalanche amplification of the parallel reflector, which is called laser light for short.Figure1. Laser2.2 Important Characteristics of Laser（1）High directivity, small divergence angle of light speed, the laser beam extends only a few centimeters from a few kilometers away.（2）High monochromaticity, the frequency width of laser light is more than 10 times smaller than that of ordinary light.（3）High brightness, laser beam convergence can produce temperatures up to several million degrees.2.3 Types of LaserLaser can be divided into four types according to working substance:（1）Solid state laserIts working substance is solid. Ruby laser, neodymium doped yttrium aluminum garnet laser (i.e. YAG laser) and neodymium glass laser are commonly used. Their structures are basically the same, characterized by small and solid, high power. At present, neodymium glass laser is the device with the highest pulse output power, which has reached tens of megawatts.（2）Gas laserIts working substance is gas. Now there are various kinds of gas atoms, ions, metal vapor, gas molecular lasers. Commonly used are carbon dioxide laser, helium neon laser and carbon monoxide laser, whose shape is like a common discharge tube, characterized by stable output, good monochromaticity, long life, but small power, low conversion efficiency.（3）Liquid laserIt can be divided into chelate laser, inorganic liquid laser and organic dye laser, the most important of which is organic dye laser. Its main feature is that the wavelength is continuously adjustable.（4）Semiconductor laserIt is a younger laser, and the more mature one is GaAs laser. It is characterized by high efficiency, small size, light weight and simple structure, and is suitable for carrying on airplanes, warships, tanks and infantry. It can be made into range finder and sighting device. However, the output power is small, the directivity is poor, and it is greatly affected by the ambient temperature.2.4 What can Laser Sensor Detect? (1) Laser measurement of lengthPrecise measurement of length is one of the key technologies in precise machinery manufacturing industry and optical processing industry. Modern length measurement is mostly based on the interference phenomenon of light wave, and its accuracy mainly depends on the monochromaticity of light. Laser is the most ideal light source. It is 100 thousand times purer than the best monochromatic light source (krypton-86 lamp). Therefore, the laser measurement range of length is large and the accuracy is high.  According to the optical principle, the relationship between the maximum measurable length L of monochromatic light and wavelength λ and spectral line width δ is L = λ 2 / δ. The maximum measurable length of krypton-86 lamp is 38.5cm. For a long object, it is necessary to measure in sections to reduce the accuracy. If He-Ne gas laser is used, it can measure tens of kilometers at most. Generally, the length within several meters can be measured with an accuracy of 0.1 μ M.Figure2. Laser Measure(2) Laser measurement of distanceIts principle is the same as that of the radio radar. After the laser is aimed at the target, the round-trip time is measured, and then the round-trip distance is obtained by multiplying the speed of light. Because of the advantages of laser, such as high directivity, high monochromaticity and high power, these are very important for the measurement of long distance, the determination of target orientation, the improvement of signal-to-noise ratio of the receiving system, and the guarantee of measurement accuracy, so the laser rangefinder is paid more and more attention.  The lidar developed on the basis of the laser rangefinder can not only measure the distance, but also the azimuth, velocity and acceleration of the target. It has been successfully used in the ranging and tracking of the artificial satellite. For example, the lidar using ruby laser has a distance measuring range of 500-2000 km with an error of only a few meters. At present, ruby laser, neodymium glass laser, carbon dioxide laser and Gas laser are often used as the light source of laser rangefinder.Figure3. Measuring Distance with Laser Sensor (3) Laser measurement of thickness Based on the principle of triangle ranging, a precise laser ranging sensor is divided at the upper and lower part of the C-frame. The modulated laser emitted by the laser hits the surface of the measured object. By sampling the signal of the linear CCD, the distance between the measured object and the C-frame is synchronously obtained by the linear CCD camera under the control of the control circuit. The thickness of the middle measured object is calculated by the data fed back by the sensor. Because the detection is continuous, the continuous dynamic thickness of the measured object can be obtained.Figure4. Thickness Measuring with Laser SensorThickness measurement by single laser displacement sensorPut the measured body on the measuring platform, measure the distance from the sensor to the platform surface, then measure the distance from the sensor to the measured body surface, and measure the thickness after calculation. It is required that there is no air gap between the measured body and the measuring platform, and the measured body is not cocked. These strict requirements can only be achieved offline.Thickness measurement by double laser displacement sensorA laser displacement sensor is installed above and below the measured body respectively, and the thickness of the measured body is d = C - (a + b). Among them, C is the distance between two sensors, a is the distance between the upper sensor and the measured body, and B is the distance between the lower sensor and the measured body. The advantage of this method for on-line thickness measurement is that it can eliminate the influence of the vibration of the measured body on the measurement results.  But at the same time, there are requirements for sensor installation and performance. The conditions to ensure the accuracy of measurement are that two sensor beams must be coaxial and that two sensor scans must be synchronous. Coaxiality is realized by installation, and synchronization depends on the selection of laser sensor with synchronization end.Figure5. Thickness MeasurementIII Laser Displacement Sensor3.1 What is Laser Displacement SensorThe laser displacement sensor is called the eyes of the robot and machine, and has an irreplaceable role in welding, blank manufacturing, mechanical processing, heat treatment, loading and unloading, assembly and other operations. So, what is a laser displacement sensor? The laser displacement sensor is a sensor that uses laser technology for measurement, and is composed of a laser, a laser detector, and a measurement circuit. As a new type of measuring equipment, the laser displacement sensor can accurately measure the position, displacement and other changes of the measured object, and can also measure precise geometric measurements such as displacement, thickness, vibration, distance, and diameter.3.2 How Does Laser Displacement Sensor Work?The laser displacement sensor can accurately and non-contactly measure the position, displacement and other changes of the measured object, and is mainly used to measure the displacement, thickness, vibration, distance, diameter and other geometric quantities of the object. According to the measurement principle, the principle of laser displacement sensor is divided into laser triangulation method and laser echo analysis method. Laser triangulation method is generally suitable for high-precision and short-distance measurement, while laser echo analysis method is used for long-distance measurement. The following is the introduction to two measurement methods of laser displacement sensor principle.TriangulationFigure6. Laser Displacement SensorThe laser emitter shoots the visible red laser to the object surface through the lens, and the laser reflected by the object passes through the receiver lens, which is accepted by the internal CCD linear camera. According to different distances, the CCD linear camera can "see" this light point at different angles. According to the distance between the laser and the camera known from this angle, the digital signal processor can calculate the distance between the sensor and the measured object. At the same time, the position of the beam in the receiving element is processed by analog and digital circuits, and the corresponding output value is calculated by microprocessor analysis, and the standard data signal is output in proportion in the analog quantity window set by the user. If switching value output is used, it will be conducted in the settings window and cut off outside the window. In addition, an independent detection window can be set for analog quantity and switch quantity output.Echo analysisThe laser displacement sensor can achieve a certain degree of accuracy by using the echo analysis principle to measure the distance. The sensor is composed of processor unit, echo processing unit, laser transmitter and laser receiver. The laser displacement sensor emits one million pulses per second through the laser transmitter to the detector and returns to the receiver. The processor calculates the time required for the laser pulse to meet the detector and return to the receiver, so as to calculate the distance value.  The output value is the average output of thousands of measurement results. It is the so-called pulse time method. The laser echo analysis method is suitable for long-distance detection, but the measurement accuracy is lower than the laser triangulation method, and the longest detection distance can reach 250m.3.3 Application of Laser Displacement Sensor(1) Dimension measurement: position identification of small parts; monitoring of whether there are parts on the conveyor belt; detection of material overlapping and covering; control of manipulator position (tool center position); device state detection; detection of device position (through the small hole); monitoring of liquid level; thickness measurement; vibration analysis; collision test measurement; automobile-related test, etc. (2) Thickness measurement of sheet metal: laser sensor measures the thickness of sheet metal. Thickness change detection can help to detect wrinkles, small holes or overlaps to avoid machine failure. (3) Cylinder measurement: angle, length, eccentricity of inner and outer diameter, conicity, concentricity and surface profile.Figure7. Application of Laser Displacement Sensor(4) Length measurement: place the measured component on the conveyor belt at the designated position, the laser sensor detects the component and simultaneously measures it with the triggered laser scanner, and finally obtains the length of the component. (5) Uniformity check: place several laser sensors in a row in the tilt direction of the workpiece movement to be measured, and directly output the measurement value through one sensor. In addition, the software can be used to calculate the measurement value and read out the result according to the signal or data. (6) Inspection of electronic components: two laser scanners are used to place the tested components between them. Finally, the data is read out by the sensor, so as to detect the accuracy and integrity of the component size. (7) Inspection of filling level in production line: laser sensor is integrated into the production and manufacturing of filling products. When the filling products pass through the sensor, it can detect whether the filling is full. The sensor can accurately identify whether the filling product is qualified and the quantity of the product by using the extended program of laser beam reflecting surface. 3.4 What are the Parameters to Know When Choosing a Laser Displacement Sensor?Some parameters that must be understood when selecting a laser displacement sensor are very important.(1) Resolution: generally refers to the minimum range of the sensor, that is, the maximum recognition rate of the sensor. If the parameter is marked as 1mm, then the resolution is equal to 1mm. (2) Repeatability: We must know that even if the measured object is at rest, the measured value will fluctuate slightly. The error margin of repeated measurement of the measured object at the same position in the static state is the repeat accuracy. For example, if the parameter is marked as 1μm, the repeat accuracy of the sensor is 1μm. (3) Full range (effective range): the rated effective range of the sensor. When selecting a sensor, we must select the sensor that contains the effective range according to the required detection distance. (4) Linear accuracy: the error between the measured value and the actual displacement. Linear accuracy is expressed as a percentage, but since the range is a range and the measurement accuracy is more difficult to reach the apex of the range, most sensors will mark the linear accuracy of the apex of the range to intuitively reflect the performance of the sensor. (5) Sampling frequency/sampling period: frequency refers to the number of measurements per second. The higher the frequency, the shorter the time it takes to make a measurement. The shorter the measurement time, the more suitable it is for the detection of high-speed moving objects. (6) Average sampling times: even in the static state, there will be slight measurement fluctuations. At this time, multiple measurements are required to calculate the average number to make the measured value stable and accurate.Figure8. Laser SensorIV Laser Distance SensorLaser ranging is one of the earliest applications of the laser. This is because the laser has many advantages such as strong directivity, high brightness, and good monochromaticity. Before 1965, the Soviet Union used a laser to measure the distance between the earth and the moon (384401km) with an error of only 250m. In 1969, the Americans landed on the moon with a retro-reflector on the lunar surface. They also used a laser to measure the distance between the earth and the moon, with an error of only 15cm. The basic principle of using laser transmission time to measure the distance is to determine the target distance by measuring the time required for the laser to travel to and from the target.Related recommendation: Proximity SensorFigure9. Laser Distance Sensor4.1 Classification of Laser Distance Sensors Laser distance sensor technology is divided into absolute distance measurement method and micro displacement measurement method according to the measurement range. Subdivided according to the measuring method, the absolute distance ranging method mainly includes pulse laser ranging and phase laser ranging, and the micro displacement measuring method mainly includes triangulation laser ranging and interferometric laser ranging.4.2 Measuring Principle of Different Laser Distance Sensors(1) Pulse Laser Distance SensorA pulse laser with a very short duration is emitted by a pulsed laser, and after reaching the target to be measured after the distance to be measured, part of the energy will be reflected back. The reflected pulsed laser is called an echo. The echo returns to the rangefinder and is received by a photoelectric detector. According to the interval between the main wave signal and the echo signal, that is, when the laser pulse travels from the laser to the target to be measured, the distance of the target to be measured can be calculated.  (2) Phase laser Distance SensorThe emitted laser light is emphasized, and the phase change of the modulated signal is used when the laser is propagated in space. According to the wavelength of the modulated wave, the distance represented by the phase delay is calculated. That is, the indirect method of phase delay measurement is used instead of directly measuring the time required for the round trip of the laser to achieve distance measurement. The accuracy of this method can reach the millimeter level.Figure10. Working Principle of Laser Distance Measuring Device (3) Triangulation Laser Distance SensorAs mentioned above, this measurement principle is that the light emitted by the laser is focused on the surface of the measured object after being focused by the condensing lens, and the receiving lens receives the scattered light from the incident light spot and images it on the photoelectric  position detector On the sensitive side. When the object moves, the relative distance of the object movement is calculated by the displacement of the light spot on the imaging surface. The resolution of triangulation laser ranging is very high, which can reach the order of microns.   Figure11. Triangulation Principle (4) Interferometric Laser Distance SensorBy moving the measured target and measuring the coherence, the distance increment measurement is completed by counting, so the sensitivity of the interferometric measurement is very high, which can reach the nanometer level.4.3 Application of Laser Distance SensorThe laser distance sensor is mainly used for: monitoring the position of moving objects; measuring the railway contact network, measuring the boundary of buildings; measuring unsuitable objects; industrial automation and intelligent production management; vehicle speed and flow statistics; industrial monitoring signal trigger control; tower crane XY positioning of crane; automatic target distance control; monitoring of ship's safe docking position; positioning of container; measurement of vehicle's safe distance; measurement of overhead cable and height limitation; measurement of width of boxes on conveyor belt.V Laser Sensor Application Case(1) Over-limit detection of vehicle width and heightThe laser sensor is used for rapid measurement, the network core of the PC industrial control computer and the visual programming software VB are used for real-time data transmission and processing, and the friendly interface control software is also designed. Field test data shows that the system has good real-time performance and high measurement accuracy, and has certain practical value. (2) Expressway toll stationUsed in highway toll stations to count and protect vehicles. Malaysian Teras has applied hundreds of BEA laser sensors to its manual and automatic toll station systems. The laser sensor uses the time-of-flight (TOF) measurement principle, which can form 4 planes in the detection area to detect the vehicle. At the same time, the product also has functions such as anti-collision and vehicle safety protection. Compared with the traditional light curtain, the laser sensor has the advantages of high sensitivity, high accuracy, easy installation, high cost performance and strong stability. (3) Google's second-generation unmanned vehicleIn addition to the laser sensor on the top, Google’s second-generation driverless car prototype is still quite obvious, and the other sensors are set very concealed. The front, rear and sides of the vehicle are clearly marked with the Google unmanned vehicle logo. The driving principle of Google's unmanned vehicle is to continuously collect various accurate data of the vehicle itself and the surroundings through many sensors installed around the car, analyze and calculate it through the processor in the car, and then control the driving of the car according to the calculation results . Unmanned vehicles will use GPS equipment and sensors to accurately locate the vehicle's position and speed, and judge pedestrians, vehicles, bicycles, signal lights and many other objects around it.Figure12. Google's Self-driving CarThe roof of this Lexus is equipped with a 360° rotating laser holographic sensor, which can sense the front, side and rear conditions of the car almost simultaneously. The data collected by the sensor will be input to the processor located on the right rear side of the vehicle through the green data line. This laser sensor can also allow unmanned vehicles to be accurately positioned globally. The original L-shaped Lexus logo on the front of the car was also removed and replaced with a radar sensor; it was used to measure the distance ahead and the speed of the vehicle in order to determine the condition of the vehicle ahead and control the safe acceleration and deceleration of the vehicle. The wheel hub of the tire is also equipped with a position sensor, which is used to detect wheel rotation and help the vehicle to locate. The heart of Google's unmanned vehicles-the processor is located on the right rear side of the vehicle, the data information from each sensor will be transmitted here through the data wire, and analyzed and processed through the software in order to accurately sense and judge the difference between the unmanned vehicles object. In addition to analyzing and judging the current position of objects around the unmanned vehicle, the unmanned vehicle also needs to be calculated by software to accurately predict the possible next position of each object. Finally, the unmanned car will make safe driving decisions based on all the collected data, including controlling the speed of the car and the surrounding distance. VI FAQ1. How does laser sensor work?The basic principle is optical triangulation using a CMOS linear imager. A diffuse triangulating laser distance sensor transmits a laser through a lens and to the target, which reflects the light back to the sensor. A lens focuses this reflected light into a small spot onto the CMOS linear imager. 2. What is the use of laser sensors?The definition of a laser sensor is, it is an electrical device used to sense minute objects and precise positions. This sensor uses a laser to produce light within a straight line. Its visible ray mark of the laser makes the arrangement very simple. Laser light includes light waves with similar wavelengths. 3. What are the types of laser sensors?Laser distance sensors.Displacement sensors.Laser projectors.Laser light curtains.Laser photoelectric sensors.Positioning lasers.Laser edge detection sensors. 4. Are laser sensors dangerous?Improperly used laser devices are potentially dangerous. Effects can range from mild skin burns to irreversible injury to the skin and eye. The biological damage caused by lasers is produced through thermal, acoustical and photochemical processes. 5. Is a laser a sensor?A laser sensor uses a 'laser' to emit light in a straight line. Its visible beam spot makes alignment and positioning very easy. Since the light beam is focused, the sensor can be installed without worries about stray light. The major types of laser sensors include reflective, thru beam, and retro-reflective. 6. What is the range of the laser sensor?Laser distance sensors are designed for non-contact distance measurements: laser gauges for measuring ranges up to 10m, laser distance sensors for up to 3,000m. 7. What is CMOS Laser Sensor?A CMOS image sensor combines with a step-less laser power adjustment algorithm to produce stable detection of all types of workpieces from black rubber with low reflectivity to stainless steel and other highly glossy materials. 8. Which laser sensor is used for measuring very long distances?LDM301 laser distance sensor series – fast measurement of long distances. The laser distance sensors of the LDM301 series use a measured time-of-flight principle to measure distances of 300 m for natural surfaces and 3,000 m for reflective surfaces. 9. How does a laser sensor measure distance?The distance measurement is based on the triangulation principle. The laser beam strikes the object as a small point. The receiver of the sensor (photodiode line) detects the position of this point. The angle of incidence changes according to the distance, and thereby the position of the laser point on the receiver. 10. How accurate are laser distance sensors?Compared to other types of laser sensors, OM70 sensors feature one of the thinnest beam shapes, helping to ensure a more precise measuring focus. For example, most point-type lasers typically only go down to 0.2mm x 0.75mm whereas the OM70 goes down to 0.05mm x 0.05mm. 

  In daily production and life, ultrasonic ranging sensors are mainly used for non-contact automatic parking distance control (PDC) of automobiles, obstacle avoidance robots, construction sites and industrial working environments that require liquid level, well depth, pipeline length, etc. In general, there are two commonly used ultrasonic distance measurement methods:   - The ultrasonic ranging system based on single chip microcomputer or embedded equipment;   -  An ultrasonic ranging system based on CPLD (complex programmable logic device). In order to understand the design and application of ultrasonic ranging sensor, let us first understand the working principle of ultrasonic sensor. Introducing ultrasonic sensor & taking HC-SR04 as an example   Catalog   I What is ultrasonic sensor? II Methods for ultrasonic ranging III Principles for ultrasonic ranging IV Conclusion FAQ   I What is ultrasonic sensor?      Figure 1. Working principle of ultrasonic sensor ranging An ultrasonic sensor is a sensor that converts an ultrasonic signal into another energy signal (usually an electrical signal).  Ultrasonic is a mechanical shock wave generated in elastic media with a frequency greater than 20 kHz. Because of its strong directivity, slow energy consumption and relatively long propagation distance, it is often used in non-contact ranging.  In addition, ultrasonic has the big ability to penetrate liquid and solid, especially in the sunshine opaque solid. When an ultrasonic hits an impurity or an interface, itwill produce a significant reflection to form an echo,  and when it hits a moving object will cause a phenomenon called Doppler Effect.  Therefore, ultrasonic ranging has a good adaptability to the environment, and ultrasonic distance measurement can be well compromised in real time, precision, and price. II Methods for ultrasonic ranging At present, there are various methods for ultrasonic ranging:    -  round-trip time detection;   -  phase detection;   -  acoustic amplitude detection. The principle is that the ultrasonic sensor emits ultrasonic waves of a certain frequency, propagates through the air medium, and is reflected back after reaching the measurement target or the obstacle. After being reflected, the ultrasonic receiver receives the pulses, and the time it takes, is the round-trip time, which is related to the distance traveled by ultrasonic waves. Measuring the wave propagation time to get the wave propagation distance: Assuming that s is the distance between the measured object and the range finder, the time measured is t / s, and the velocity of ultrasonic propagation is expressed as v／m·s－1, then there is a relation (1): s=vt／2       (1) When the accuracy is required, the influence of temperature on the ultrasonic propagation speed needs to be considered, therefore the ultrasonic propagation speed is corrected according to relation (2) to reduce the error. v=331．4+0．607T        (2) Where T is the actual temperature, the unit is °C; v is the propagation speed of ultrasonic wave in the medium, and the unit is m/s. Figure 2. Working principle of ultrasonic ranging sensor   III Principles for ultrasonic ranging   The principle of ultrasonic ranging is to transmit ultrasonic waves in a specific direction through an ultrasonic transmitter, and start timing at the same time as the transmission. When ultrasonic waves propagate in the air and hit an obstacle, they will immediately return and be received by the ultrasonic receiver, and stop timing immediately. The ultrasonic ranging sensor uses the principle of ultrasonic echo ranging and uses precise time difference measurement technology to detect the distance between the sensor and the target. It has the advantages of small angle, small blind area, high measurement accuracy, non-contact ranging, waterproof, anti-corrosion, and low cost. Ultrasonic ranging sensors are usually used in a way that one transmitter corresponds to one receiver, but there are also multiple transmitters corresponding to one receiver. Therefore, the ultrasonic distance sensor can measure the return and return time of the ultrasonic wave to determine the distance of the object. This is how the ultrasonic distance sensor works. For the ultrasonic distance sensor, we recommend to use the Korean Hagisonic ultrasonic distance sensor module HG-C40U.   Figure 3. Ultrasonic distance sensor module HG-C40U   Ultrasonic distance sensor module has two optional transmission modes:   -  Free operation mode: when there is power supply, the sensor itself can send trigger and burst signals and it is usually for basic applications;   -  External trigger mode: the external system (controller or processor) controls trigger signals for advanced applications. These two modes are suitable for a variety of purposes.   In addition, the sensors also involve the choice of two input power supplies:   -  Low voltage (5V) for the processor circuit, the distance to the obstacle can be measured is 3.5m;   -  High voltage (12V) for the controller circuit, the distance to the obstacle can be measured is 5m. The data is transmitted by UART (universal asynchronous receiver-transmitter) with a resolution of less than 5mm. On the other hand, users can select different setting modes according to their own environment needs. Such as free-running / UART triggering / external trigger settings, etc.  At the same time, on the basis of baud rate of UART communication, the user can also decide whether to set up the circular buffer or not. The output signal uses high performance ASIC (application-specific integrated circuit) chip to ensure stable transmission and sensitive reception, and the communication between sensor and PC uses "interface board" (RS232, power regulator). The data show that the real received ultrasonic wave can be amplified in real time by using the monitor program on PC, the distance value can be output by UART (ASCII, mm), and then the detection signal can be converted into the rectangular TTL level signal (square wave) in real time. IV Conclusion Ultrasonic sensors are reliable, cost-effective and efficient solutions for distance sensing, level and obstacle detection. Once you understand how ultrasonic sensors work and which ultrasonic technology is most suitable rather than excellent, you can make more informed decisions about the correct sensor system for your application.   FAQ   1. What type of sensor is ultrasonic sensor? ultrasonic / level sensors measure the distance to the target by measuring the time between the emission and reception. An optical sensor has a transmitter and receiver, whereas an ultrasonic / level sensor uses a single ultrasonic element for both emission and reception.   2. How many types of ultrasonic sensors are there? four types. All together there are four types of ultrasonic sensors, classified by frequency and shape: the drip-proof type, high-frequency type, and open structure type (lead type and SMD type).   3. What is the range of ultrasonic sensor? For ultrasonic sensing, the most widely used range is 40 to 70 kHz. The frequency determines range and resolution; the lower frequencies produce the greatest sensing range. At 58 kHz, a commonly used frequency, the measurement resolution is one centimeter (cm), and range is up to 11 meters.   4. Can ultrasonic sensor detect human? Finally, ultrasonic sensors assist in detecting people for autonomous navigation of robots. Ultrasonic sensors can be used to set multiple tripwire distances to help navigate around people. Additionally, the high read rate allows you to quickly detect when a person may enter your robot's path.   5. Is ultrasonic sensor harmful? Occupational exposure to ultrasound in excess of 120 dB may lead to hearing loss. Exposure in excess of 155 dB may produce heating effects that are harmful to the human body, and it has been calculated that exposures above 180 dB may lead to death.   6. How do ultrasonic sensors work? Ultrasonic sensors work by emitting sound waves at a frequency too high for humans to hear. They then wait for the sound to be reflected back, calculating distance based on the time required. This is similar to how radar measures the time it takes a radio wave to return after hitting an object.   7. Why is ultrasonic sensor used? Ultrasonic sensors are used primarily as proximity sensors. They can be found in automobile self-parking technology and anti-collision safety systems. ... Ultrasonic sensors are also used as level sensors to detect, monitor, and regulate liquid levels in closed containers (such as vats in chemical factories).   8. Where are ultrasonic sensors used? Ultrasonic sensors have been used throughout many applications and industries. They are used within food and beverage to measure liquid level in bottles, they can be used within manufacturing for an automated process and control maximising efficiency on the factory floor.   9. Is ultrasonic sensor waterproof? Most ultrasonic distance sensors aren't waterproof which can be a problem if you need your project to withstand the elements outdoors. ... This sensor is suitable for outdoor applications such as car reversing sensors, security alarms, industrial inspection, etc.   10. Is ultrasonic sensor analog or digital? Usually, ultrasonic sensors are integrated with an Analog-to-Digital converter (ADC).   11. How do ultrasonic sensors measure distance? As the name indicates, ultrasonic sensors measure distance by using ultrasonic waves. The sensor head emits an ultrasonic wave and receives the wave reflected back from the target. Ultrasonic Sensors measure the distance to the target by measuring the time between the emission and reception.   12. How accurate is the ultrasonic sensor? The more accurate ultrasonic sensors can achieve 0.1 – 0.2% of the detected range under perfectly controlled conditions, and most good ultrasonic sensors can generally achieve between 1% and 3% accuracy.   13. What can ultrasonic sensors detect? Ultrasonic sensors can measure the distance to a wide range of objects regardless of shape, color or surface texture. They are also able to measure an approaching or receding object.   14. Are ultrasonic sensors affected by smoke? Ultrasonic sensors are superior to infrared sensors because they aren't affected by smoke or black materials, however, soft materials which don't reflect the sonar (ultrasonic) waves very well may cause issues.   15. Which is better ultrasonic or IR sensor? Ultrasonic sensors work using sound waves, detecting obstacles is not affected by as many factors. If reliability is an important factor in your sensor selection, ultrasonic sensors are more reliable than IR sensors. If you're willing to compromise reliability for cost, infrared sensors are ideal for your application.