A position sensor is a sensor that senses the position of the measured object and converts it into a usable output signal. It can sense the position of the measured object and convert it into a usable output signal sensor.Motion & Position Sensors

 

Position sensors are sensors that measure position. It can be divided into absolute position sensor and relative position sensor (displacement sensor). Classified according to the nature of the measured variable, position sensors can be classified as linear, angular and multi-axis.

 

Ⅰ. Introduction of position sensor

 

1.IMU - Inertial Measurement Unit: It is a sensor module that integrates multiple inertial sensors to measure the three-dimensional motion and attitude of an object. It usually consists of sensors such as accelerometers, gyroscopes and magnetometers, which can provide information such as acceleration, angular velocity and magnetic field of objects.

 

By integrating sensors such as accelerometers, gyroscopes, and magnetometers, IMUs can provide comprehensive motion and attitude information of objects. By collecting and processing the output of these sensors, parameters such as the position, velocity, acceleration, angular velocity, direction and attitude of the object can be calculated. IMUs are widely used in navigation systems, drones, robotics, virtual reality, motion tracking, and more.

 

Accelerometer: An accelerometer is a common motion sensor that measures the acceleration of an object. It can detect the linear acceleration of the object in three axes and convert it into a corresponding electrical signal output. The working principle of the acceleration sensor is usually based on microelectromechanical system (MEMS) technology, which uses a spring with a small mass and the relative displacement of the mass to measure the acceleration. Acceleration sensor types are divided into piezoresistive acceleration sensors and capacitive acceleration sensors.

 

Piezoresistive Accelerometer: A piezoresistive accelerometer uses a tiny piezoresistive element to measure acceleration. When an object accelerates, the piezoresistive element experiences a change in pressure or stress, causing its resistance value to change. This changing resistance value is converted to an electrical signal output related to acceleration.

 

Capacitive Accelerometer: A capacitive accelerometer uses a change in capacitance to measure acceleration. It consists of a fixed electrode and a moving mass that is displaced relative to the electrode as the object accelerates, causing a change in capacitance. This changing capacitance value is converted to an electrical signal output related to acceleration.

 

Gyroscope: Gyroscopes are used to measure the angular velocity or rate of change of an object. It is capable of detecting rotation and rotation of objects around three axes. Gyroscopes can be based on MEMS technology or other principles to measure angular velocity by sensing the inertial force generated when rotating. The output of the gyroscope is usually a three-axis angular velocity vector, representing the angular velocity of the object in each axis. The working principle of the gyroscope is usually based on the law of conservation of angular momentum, which measures the angular velocity by sensing the inertial force or other physical effects generated when rotating. Gyroscopes are usually three-axis, ie capable of measuring the angular velocity of an object about the x, y and z axes. This allows the gyroscope to provide information about the rotation of an object in three dimensions.

 

Common types of gyroscopes are: optical gyroscopes and MEMS gyroscopes.

 

Optical Gyroscope: An optical gyroscope uses the interference principle of light to measure angular velocity. It includes parts such as light source, optical path and detector. As the object rotates, the light beams interfere in the optical path, and the angular velocity is measured by detecting the interference effect. Optical gyroscopes usually have high precision and stability, and are widely used in precision navigation and inertial navigation systems.

 

MEMS gyroscopes: MEMS gyroscopes are based on microelectromechanical systems (MEMS) technology and use tiny mass springs and masses to measure angular velocity. When the object rotates, the mass block will generate corresponding displacement or vibration, and these changes will be converted into electrical signal output related to angular velocity through the sensing element.

 

Magnetometer: Used to measure the strength and direction of the magnetic field around an object. It can provide information about the orientation of objects relative to the Earth's magnetic field, helping to determine the attitude or navigation of objects. A magnetometer can measure the direction and strength of a magnetic field by sensing changes in the magnetic field based on principles such as the Hall effect or the magnetoresistance effect. The output of a magnetometer is usually a three-axis magnetic field vector, representing the magnetic field strength of the object in each axis. Magnetometers are widely used in navigation systems, aerospace, robotics, geomagnetic positioning, attitude control, and magnetic field measurement. For example, in navigation systems, magnetometers can be used in compass functions to help measure and determine the orientation of objects. In robotics, magnetometers are used for navigation and landmark recognition. In magnetic field measurement, the magnetometer can be used for the measurement of magnetic field strength and geological exploration.

 

2. Inclinometer: also known as tilt sensor or tilt sensor, used to measure the tilt angle or slope of an object relative to the direction of gravity. It is a sensor specially used to measure the degree of inclination or the direction of inclination of an object. Common types of inclinometers are optical inclinometers, liquid inclinometers, MEMS inclinometers, and capacitive inclinometers.

 

The characteristics of the inclinometer: the portable digital vertical activity inclinometer is famous for its durability, high precision and fast response; in order to ensure that it can also detect on various inclinometer pipes, the inclinometer probe is equipped with a strong wheel frame, sealed Axle and specially designed measuring wheel; each inclinometer probe is strictly calibrated by a specially designed computer calibration workbench; the control cable is very durable and easy to carry, and can maintain flexible and durable characteristics even at low temperatures. The control cables are also chemically and abrasion resistant and offer excellent dimensional stability. Flexible rubber depth markers are permanently and reliably hardened on the cable jacket. Markers will not come loose and there will be no burrs that could damage the cable jacket and wires.

 

3. Distance sensor: A device used to measure the distance between an object and the sensor. They use different principles and techniques to sense and measure the distance of an object and convert it into a corresponding output signal. Common distance sensor types are millimeter-wave radar sensors, infrared sensors, time-of-flight sensors, ultrasonic sensors, and laser sensors.

 

4. Global Positioning System (GPS): GPS sensors are used to measure the geographic location and velocity of objects. It is a technology that provides global positioning and navigation services through satellite systems. The GPS system consists of a group of satellites operating in medium orbits. Currently, there are 30 satellites in the GPS system, and they are distributed around the globe in different orbits. These satellites send signals to the ground with accurate orbit and clock information. A GPS receiver is a device used to receive and process satellite signals. The receiver works by receiving signals from at least 4 satellites and measuring the arrival time of the signals and the satellite position information. Through the principle of triangulation, the receiver can calculate its own position, speed and time.

 

5. Ultrasonic Sensors:Ultrasonic sensors use the reflection and travel time of sound waves to measure the distance between an object and the sensor. They are commonly used in applications such as obstacle avoidance, distance measurement, and position detection. The acoustic wave sensor contains a transmitter inside, which emits a series of ultrasonic pulse signals. Typically, the frequency of the pulses is between 20kHz and 200kHz, which is beyond the range of human hearing. By measuring the time difference between the transmission and reception of the ultrasonic pulse signal, the distance between the object and the sensor can be calculated. Velocity is distance divided by time, so by knowing the speed at which ultrasonic waves travel through air (about 343 m/s), distance can be calculated using the time difference.

 

Ⅱ. Types of Position Sensors

 

1. Pull wire sensor: It is a sensor used to measure the linear displacement or position of an object. They usually consist of a pull wire or rope with sensors attached to it. Pull wire sensors are attached to an object using a cord or wire and measure position by measuring the length of the wire stretched or retracted. Pull wire sensors typically use the potentiometer principle to measure changes in the length of a pull wire. The advantage is that a larger measurement range and higher resolution can be achieved. They are suitable for applications that require the measurement of linear displacement, such as industrial automation, mechanical systems, aerospace, construction engineering, etc.

 

2. Photoelectric encoder: It is a commonly used position sensor used to measure the angular or linear displacement of an object. It converts the position change into an electrical signal output by using a photoelectric sensor and an encoder disc. Optical encoders use the principles of optics to measure the position of an object. It usually consists of light source, grating, receiver and signal processing circuit. The grating has a specific pattern. When the object moves, the light on the grating is detected by the photoelectric element between the light source and the receiver, thereby measuring the position and speed of motion. Photoelectric encoders have the advantages of high resolution, high precision and fast response. They can be used to measure parameters such as rotation angle, linear displacement, velocity and acceleration, and are suitable for various application fields such as robotics, CNC machine tools, medical equipment, optical instruments and automation systems, etc.

 

3. Capacitive encoder: It is a sensor used to measure the angle or linear displacement of an object, and it realizes position measurement based on the change of capacitance. It converts the position change into an electrical signal output by using a photoelectric sensor and an encoder disc. Capacitive encoders use changes in capacitance to measure the position of an object. It uses the capacitance change between an object and a capacitive sensor to measure position and motion, usually by detecting the capacitance value or relative capacitance change of a capacitive sensor.

 

4. Magnetic encoder: It is a sensor used to measure the angle or linear displacement of an object, which uses changes in the magnetic field to achieve position measurement. Magnetic encoders use the principle of a magnetic field to measure the position of an object. It includes a magnetic marker and a magnetic sensor. The magnetic marker generates a magnetic field through a magnetic material fixed on the object, and the magnetic sensor is used to detect and measure changes in the magnetic field to determine the position of the object. Since no direct contact is required between the magnetic sensor and the magnetic marker, magnetic encoders are non-contact and wear-free, providing long-term stable measurement results.

 

5. Laser ranging sensor: It is a sensor that uses laser technology for precise distance measurement. It uses the emission and reception of laser beams to measure the distance between the object and the sensor. Laser ranging sensors use the emission and reception of laser beams to measure the distance between an object and the sensor. It determines the position of an object by measuring the travel time of a laser beam or the phase difference of light.

 

Ⅲ. Factors affecting the accuracy and stability of the position sensor

 

1. Power supply stability: The position sensor has high requirements on the stability of the power supply voltage. Unstable supply voltages can cause inaccurate or fluctuating output signals, reducing sensor accuracy and stability.

 

2. Environmental conditions: Environmental conditions can have a significant impact on the performance of a position sensor. Changes in temperature, humidity, vibration, and electromagnetic interference can all affect sensor accuracy and stability. Therefore, in order to maintain the accuracy of the sensor, it needs to be used under suitable environmental conditions.

 

3. Signal processing and filtering: The output signal of the sensor usually requires signal processing and filtering to remove noise and interference. Proper signal processing and filtering methods can improve the accuracy and stability of the sensor.

 

4. Mechanical mounting and positioning: Proper mechanical mounting and positioning are critical to the accuracy of the position sensor. When installing, make sure that the physical connection between the sensor and the object to be measured is good, and that the sensor position is correct.

 

Ⅳ. Eight development trends of sensors

 

Since the birth of the sensor, it can help human beings turn the once unknowable and difficult-to-judge information into easy-to-obtain and more accurate data. The application scenarios of sensors are becoming more and more abundant.

 

1. Medical application

 

As the miniaturization of laboratory systems will accelerate the development of emerging technologies for biohazard sensing, wearable sensors will become true medical-grade devices. Make the detection easier, a detection instrument can analyze more substances, and reduce the demand for detection sample volume.

 

2. Better perception and more data

 

Future sensors will more effectively mimic human senses to detect, process, and analyze complex signals such as biohazards, odors, material stress, pathogens, and corrosion.

 

3. Small size and low cost

 

With the application of various new platforms and new materials, manufacturers can make smaller sensors, whose performance can be as high as millimeter-scale and microwave-scale electronic components, and with the application of less silicon, the cost will be greatly increased. The magnitude is reduced.

 

4. Higher accuracy

 

At present, the research on multi-channel cooperative spectrum sensing is still in the early stage. Once the technology matures in the future, it will provide more accurate monitoring data than the current single-channel sensor. More accurate, reliable and reproducible sensors will be used in medical equipment, etc. The field has more application scenarios, and the realized functions are more powerful.

 

5. Flexible and Flexible

 

Flexible sensors are an important direction for future sensor development. Currently, flexible photosensors, pH sensors, ion sensors, and biosensors are still in the early stages of development. In the future, these flexible sensors will have more innovative applications, such as artificial skin, wearable sensors, and micro-motion sensing. Through micro-wire technology and magnetic fields, the sensors can be as thin as a hair, yet flexible, and do not require a power source. Temperature, pressure, tension, stress, torsion and position can be measured without contact.

 

6. More energy efficient

 

In the future, sensors will be smarter and condition-driven, activated only when a certain condition is met, and consume little to no power when they are in standby mode. In addition, the sensor can also obtain energy from the surrounding environment to achieve longer operation, such as motion, pressure, light, or the difference in heat between the patient's body and the surrounding air, etc. can become the energy source of the sensor.

 

7. More environmentally friendly

 

In the future, environmentally friendly and biodegradable sensors will become increasingly popular. For example, the sensor can use degradable paper-based batteries powered by bacteria, which can be used in fields such as farmland management, environmental monitoring, food distribution monitoring or medical detection without polluting the environment.

 

8. Higher complexity and better compatibility

 

By working in harmony, sensors gain additional complexity. Clusters of sensors allow for better coordination of work among sensors and self-learning systems to determine what and where to work. In addition, the adoption of various new technologies will also make sensors more diverse. In the future, advances in various basic sciences will further promote the rapid evolution of sensor technology. Sensors will become more miniaturized, humanized, and more friendly to human-computer interaction. At the same time, they will become more invisible and less detectable. As sensors become more deeply integrated into our daily lives and merge with new technologies such as AI, they will make our lives better in a future connected and automated world.

 

Frequently Asked Questions

 

1. How to deal with noise and interference in position sensors?

 

Noise in the sensor output signal can be reduced by using proper filtering techniques. Filtering can be implemented with digital or analog filters to suppress high frequency noise or other interfering signals. The filter design should be optimized according to the actual application requirements to balance signal smoothness and real-time response performance.

 

Increasing the sampling rate of the sensor can better capture noise and interference in the signal, and use appropriate signal processing algorithms for filtering and suppression.

 

Regular sensor calibration and compensation can reduce the effects of noise and interference. The system error and drift of the sensor can be detected and eliminated through calibration and compensation, making the output signal more accurate and stable.

 

2. How long is the response time of the position sensor?

 

Position sensors have fast response times and can provide measurement results within milliseconds or even microseconds. Response times for position sensors can also vary by sensor type, manufacturer, and specific application. Different position sensors have different response times, and the speed at which they measure and output depends on factors such as the sensor's inner workings, circuit design, and signal processing.

3. Is the working principle of the position sensor suitable for high temperature or low temperature environment?

The operating principle and applicable temperature range of position sensors vary by sensor type and design. Some position sensors will work well in high or low temperatures, while others may be sensitive or not suitable for use in extreme temperatures.