Contents:

1. Understand position sensors
2. Considerations for selecting a position sensor
3. Description of common position sensors
3.1 Potentiometer
3.2 Photoelectric position Sensor (encoder)
3.3 Magnetic position sensor
3.4 Magnetostrictive position sensor
3.5 Capacitive position sensor
3.6 Inductive Position Sensor (LVDT/RVDT)
3.7 Ultrasonic position sensor
3.8 Laser position sensor
4. Select a step for the position sensor
5. Practical application cases
6. Conclusion

I believe that in the face of diverse choices, every friend who needs to buy a position sensor will be confused - how should you choose the one that best suits your needs? Position sensors play an important role in modern technology and are widely used in smart phones, autonomous vehicles, drones, smart homes, industrial automation and other fields. Choosing the right position sensor can not only improve the accuracy and reliability of the system, but also reduce energy consumption and cost. Here, Chipqry provides you with a detailed guide to the key factors to consider when choosing a location sensor, making it easy to find a location sensor that meets your budget and performance requirements.

1. Understand position sensors

A position sensor is a device used to detect the position, direction, or motion state of an object. Common position sensors include magnetic sensors, optical sensors, gyroscopes, accelerometers, GPS sensors, etc. These sensors detect position information through different principles and convert it into an electrical output for subsequent processing and application.

2. Considerations for selecting a position sensor

A number of factors need to be considered when selecting a position sensor to ensure that the selected sensor will meet the needs of the application and provide reliable performance.

Here are the main considerations when choosing a position sensor:

Measuring range

Determine the maximum distance the sensor needs to cover, such as 0-100mm, 0-1m, etc. Determine the maximum Angle range that the sensor needs to measure, such as 0-360°, 0-180°, etc. If you need to measure the position of multiple axes at the same time, make sure the sensor supports multi-axis measurement.

Accuracy and resolution

The difference between the sensor measurement and the true value is usually expressed in percentages or millimeters per degree, such as ±0.1%, ±0.1mm, or ±0.1°. Minimum input variation that the sensor can distinguish, e.g. 0.01mm, 0.01°. The consistency of the sensor when measuring the same position multiple times under the same conditions.

Response speed

The time it takes for the sensor to change from input to output stability, usually in milliseconds (ms) or microseconds (μs). How many measurements can the sensor make per second, usually in Hertz (Hz).

Working environment

The ability of the sensor to function properly within the expected temperature range, such as -40°C to +85°C. Whether the sensor is resistant to moisture, such as 0% to 95% relative humidity. Whether the sensor is sensitive to electromagnetic interference and whether shielding measures are required. Whether the sensor can withstand physical stresses such as vibration and shock, and whether it has a seismic design.

Installation space

The physical dimensions of the sensor meet the requirements of the installation space, for example, diameter x length. Whether the sensor has a specific mounting or fixing method, such as threaded mounting, fixture fixing, etc. Whether the sensor can be mounted in different directions, such as vertical, horizontal.

Power requirements

Whether the sensor's power requirements are compatible with existing systems, such as 5V DC, 12V DC, 24V DC. Whether the power consumption of the sensor is within the acceptable range, such as <50mA, <100mA.

Interface compatibility

Whether the sensor outputs analog signals (e.g., 0-10V, 4-20mA) or digital signals (e.g., PWM, frequency). Whether the sensor supports the required communication protocols, such as I2C, SPI, CAN, Modbus, etc. The data format output by the sensor meets the requirements of the control system, such as ASCII and binary.

cost-effectiveness

Whether the cost of the sensor is within the budget range, including the purchase cost and installation cost. The balance between the performance of the sensor and the price is worth it. Consider maintenance, calibration and replacement costs over the long term.

Reliability and durability

The performance stability of the sensor over a long period of use, whether regular calibration is required. The durability of the sensor in harsh environments, such as corrosion and wear resistance. The expected service life of the sensor, for example 1 million cycles.

Maintenance and support

Technical support and quality of service provided by suppliers, e.g. technical documentation, training, after-sales service. Whether the sensor is easy to maintain and replace, and whether spare parts are available. Whether the sensor has a self-diagnostic function to detect and report faults.

Special requirements

If applied in flammable and explosive environments, the sensor has the appropriate explosion-proof certification, such as Ex ia IIC T6. Whether the sensor is waterproof or dust-proof, such as IP67 or IP68. Whether the sensor can work properly in high vibration environments, such as vibration frequency range and acceleration range.

Regulations and standards

Sensors comply with relevant industry standards and specifications, such as ISO, IEC standards. The sensor has passed the necessary safety certifications, such as CE, UL, and RoHS.

Application specific requirements

Some applications may require the sensor to have specific functions, such as self-diagnosis, self-calibration, temperature compensation, etc. Whether the sensor is easy to integrate with existing control systems or other devices, such as PLC, SCADA systems. Whether the provider provides customized services to meet specific application needs.

User experience

Whether the sensor is easy to install, configure and operate. Whether the sensor is equipped with a user-friendly interface, such as display, indicators, etc. Does the vendor provide detailed user manuals, programming guides, and technical support documentation?

3. Description of common position sensors

potentiometer

A potentiometer is a device that determines the position of an electrical contact by measuring the voltage drop along a resistance bar. It is characterized by simple structure, low cost and easy integration, but it also has the problem of easy wear, especially in high vibration environments. Due to these characteristics, potentiometers are widely used in low-cost automobiles and household appliances.

Depending on the mode of operation, potentiometers can be divided into contact type and provide analog output. In terms of function, there are many types of potentiometers to adapt to different application scenarios, such as linear potentiometers for position detection of linear motion, rotary potentiometers for Angle detection of rotary motion, and sliding potentiometers are often used for devices that require manual adjustment, such as volume control.

Photoelectric position sensor (encoder)

Photoelectric position sensors, also known as encoders, work by using the interaction between a light source (such as an LED) and a photosensitive element (such as a phototransistor) to accurately measure position by detecting changes in the light beam passing through or reflecting off the grating. Such sensors are characterized by their ability to provide high resolution and accuracy, but they are more sensitive to external contaminants such as dust and moisture. Therefore, photoelectric position sensors are often used in situations where high precision positioning is required, such as CNC machine tools and robotics.

According to the operating mode classification, photoelectric position sensors can be non-contact and provide digital output. From a functional point of view, the photoelectric position sensor includes two main types: incremental encoder and absolute encoder. The former measures the relative position change through the output pulse signal, and the latter assigns a unique code to each position to achieve the absolute position measurement. In addition, according to the different motion forms, the photoelectric position sensor can be subdivided into linear encoders for linear motion position detection and rotary encoders for rotary motion Angle detection.

Magnetic position sensor

Magnetic position sensors detect position based on changes in the magnetic field, most commonly using Hall effect sensors. A significant advantage of this type of sensor is that it is not sensitive to pollution and is very suitable for applications in harsh environments such as automotive and industrial automation. However, magnetic position sensors may also have hysteresis effects, which will affect their measurement accuracy to some extent. Magnetic position sensors are non-contact and can provide digital or analog output.

According to the specific function, the magnetic position sensor can be divided into several types: Hall effect sensor is mainly used to detect the change of magnetic field strength, suitable for switch or position detection; The magnetoresistive sensor uses the magnetoresistive effect to detect the direction and strength of the magnetic field, which is suitable for Angle or position detection. The magnetic encoder achieves high precision position detection by combining magnetic coding disk and magnetic sensor.

Magnetostrictive position sensor

Magnetostrictive position sensors take advantage of the properties of magnetostrictive materials to determine position by measuring the travel time of magnetic waves through the material. This sensor is characterized by non-contact measurement and is particularly suitable for applications in extreme environments such as high pressure and high temperature, despite its relatively high cost.

Magnetostrictive position sensors can provide analog or digital output, which can be divided into linear magnetostrictive sensors and rotary magnetostrictive sensors according to the different use scenarios. Among them, linear magnetostrictive sensors are mainly used for position detection of linear motion, which is commonly used in liquid level measurement. The rotating magnetostrictive sensor is suitable for the Angle detection of rotating motion.

Capacitive position sensor

Capacitive position sensors work by detecting changes in capacitance between two electrodes to measure position. Features include simple structure and low power consumption, but such sensors are susceptible to changes in temperature and humidity. Therefore, they are most suitable for applications where environmental conditions are not high. Capacitive position sensors are non-contact and usually provide an analog output.

According to the specific application requirements, capacitive position sensors can be divided into several types: linear capacitance sensors are mainly used for position detection of linear motion; The planar capacitance sensor is suitable for two-dimensional position detection. Non-contact proximity sensors can be used to detect the proximity of objects.

Inductive position sensor (LVDT/RVDT)

Inductive position sensors, such as linear variable differential transformers (LVDT) and rotary variable differential transformers (RVDT), are designed based on the principle of electromagnetic induction to measure position by detecting changes in the position of the magnetic core in the coil. This type of sensor is known for its high precision and high reliability, which is very suitable for harsh working environments, so it is widely used in aviation, military and other areas with high accuracy and reliability requirements. Inductive position sensors are non-contact and provide analog output.

According to the specific function, they can be further divided into: LVDT for position detection of linear motion; RVDT is used to detect the Angle of rotation motion. Micro-lvdts are designed for space-constrained applications.

Ultrasonic position sensor

Ultrasonic position sensor can transmit ultrasonic wave and measure the echo time to determine the distance of the target. It has the characteristics of non-contact measurement and is especially suitable for long-distance detection. However, the measurement results of such sensors can be affected by changes in temperature and speed of sound. Ultrasonic position sensors typically provide a digital output and are suitable for applications where contactless measurements are required, such as automated warehouses and vehicle back-up assistance.

According to different functions, ultrasonic position sensors can be divided into a variety of types such as single point ranging sensors, multi-point ranging sensors and ultrasonic obstacle avoidance sensors, which are used to measure the distance of a single target, simultaneously measure the distance of multiple targets, and the obstacle avoidance detection of vehicles or robots.

Laser position sensor

The laser position sensor determines the position by scanning the target with the laser beam and measuring the reflection time, which has the characteristics of high precision, high speed and large measurement range. This sensor is suitable for applications that require precision measurement and remote inspection, such as industrial production lines and scientific research. The laser position sensor is non-contact and provides a digital output.

According to the specific functions, laser position sensors can be divided into laser rangefinder, laser displacement sensor and laser scanner types, respectively, for long-distance accurate ranging, high-precision position detection and three-dimensional space position detection and modeling.

4. Select a step for the position sensor

① Clear application requirements

Determine the maximum distance or Angle range that the sensor needs to cover. Determine the required measurement accuracy and resolution. Determine system requirements for sensor response time.

Consider environmental conditions such as temperature, humidity, and electromagnetic interference at which the sensor will operate. Confirm the available mounting space and size limits.

Understand the power needs of sensors to ensure compatibility with existing systems. Determine the output signal type (analog, digital) and communication protocol (such as I2C, SPI, etc.) of the sensor.

② Preliminary screening of sensor types

Select contact (such as potentiometers) or non-contact (such as photoelectric encoders, magnetic sensors) sensors according to application requirements. Choose a linear position sensor (such as an LVDT) or a rotary position sensor (such as a rotary encoder) depending on the type of motion. Select the sensor with analog or digital output according to the requirements of the control system.

③ Evaluate candidate sensors in detail

Compare the technical parameters of each candidate sensor, such as accuracy, resolution, response time, operating temperature range, etc. Review sensor reliability data and user reviews to see how it performs in similar environments. Compare the price of different sensors and weigh the relationship between performance and cost. Inspect the supplier's technical support and service quality to ensure timely help during use.

④ Test and verify

The preliminary test is carried out in the actual application environment to verify whether the performance of the sensor meets the requirements. Evaluate the stability and reliability of the sensor over long periods of use. Test the performance of the sensor under extreme conditions such as high temperature, low temperature, high humidity, vibration, etc.

(5) Comprehensive evaluation and selection

All test results were summarized to evaluate the comprehensive performance of each sensor candidate. Select the most appropriate sensor based on the evaluation results and budget constraints. Contact the supplier to purchase the selected sensor and install and debug it.

⑥ Later maintenance and optimization

Check the working status of the sensor regularly to ensure its normal operation. In case of problems, contact the supplier or technical personnel for troubleshooting. Constantly optimize sensor configuration and system Settings based on actual usage.

5. Practical application cases

Case 1: Industrial automation

Application scenario: robotic arm position detection

Requirements:

Measuring range: 0-360°

Accuracy: ±0.1°

Response speed: ≤10ms

Working environment: In the workshop, temperature range -10°C to +50°C, vibration and dust

Installation space: Limited space at the joint of the manipulator arm

Interface compatibility: CAN communication protocol must be supported

Cost effectiveness: Medium cost

Selection process:

Preliminary screening: Consider rotary encoders and magnetic encoders.

Detailed assessment:

Rotary encoder: High precision, high resolution, but sensitive to dust.

Magnetic encoder: not sensitive to dust, suitable for harsh environments, but slightly more expensive.

Test validation: The performance of the magnetic encoder is tested in a real environment to ensure high accuracy under vibration and dust conditions.

The final choice: Choose a magnetic encoder because of its better reliability and stability in harsh environments.

Case 2: The automotive industry

Application scenario: car seat position detection

Requirements:

Measuring range: 0-500mm

Accuracy: ±1mm

Response speed: ≤100ms

Working environment: Inside the car, temperature range -40°C to +85°C, with electromagnetic interference

Installation space: Seat bottom, limited space

Interface compatibility: Support for LIN communication protocol is required

Cost effectiveness: Low cost

Selection process:

Preliminary screening: Consider potentiometers and magnetostrictive sensors.

Detailed assessment:

Potentiometer: Low cost, but easy to wear, not suitable for long-term use.

Magnetostrictive sensors: non-contact, long life, but higher cost.

Test validation: The performance of magnetostrictive sensors is tested in a laboratory environment to ensure that they maintain high accuracy in the face of electromagnetic interference and temperature changes.

The final choice: Choose a magnetostrictive sensor because of its reliability and longer life in the automotive environment.

6. Conclusion

The selection of a suitable position sensor requires comprehensive consideration of many factors. From understanding various position sensors to clarifying application requirements, to evaluating performance indicators, environmental adaptability, brand services, cost effectiveness, and laws and regulations, we can finally select the most suitable products. I hope that the above content will help you in the selection and use of position sensors.