Electrical characteristics selection

The basic form of movement of translational and rotating objects. Most of the power sources we use now are driving methods represented by rotating motors, so the (high-precision) angle sensor (or angular displacement sensor) is in a very important basic position in automatic control. An angle sensor is usually a device that converts the physical quantity of the measured object around a certain axis into an electrical signal. If there is a change in the spatial orientation of the rotation axis, on the one hand, the spatial coordinates of the rotation axis can be decomposed, such as robot booms, machining centers, etc., with 5-axis, 6-axis, and 9-axis rotation calibration. On the other hand, the space attitude sensor can be used for measurement, but it is generally difficult to achieve higher accuracy requirements, or the cost is very expensive. The angle sensor selection is a systematic process, requiring the type selector to have a more comprehensive understanding of the problems to be solved by the selected angle sensor, and have a reasonable budget for various technical indicators, installation dimensions, and price costs. How can we do a good job in the selection of angle sensors? In the first part of our series of push articles: Based on the selection of angle sensors based on the working principle, this article will provide selection references for the electrical performance parameters of angle sensors. The angle sensor has a wide range of applications in actual operation. The complex and harsh use environment in different industries and different fields will put forward different technical requirements for the angle sensor. In order to reduce the error in the measurement process and realize the electrical monitoring signal of the predetermined design accuracy, it is necessary to select a good quality angle sensor. For system designers, especially for novices, how to judge the quality of the angle sensor?

1. The choice of sensitivity Generally, within the linear range of the angle sensor, it is hoped that the higher the sensitivity of the angle sensor, the better. Because only when the sensitivity is high, the value of the output signal corresponding to the measured change is relatively large, which is beneficial to signal processing. Sensitive elements of different principles will have a large difference in sensitivity, and high sensitivity often has a certain detection interval, such as the magnetic field range and the temperature range. However, it should be noted that the sensitivity of the sensor is high, and external noise that has nothing to do with the measurement is also easy to mix in, and it will also be amplified by the amplification system and affect the measurement accuracy. Therefore, it is required that the sensor itself should have a higher signal-to-noise ratio and minimize the interference signal introduced from the outside world. The sensitivity of the sensor is directional. When the measured is a single vector, and its directivity requirements are high, the sensor with less sensitivity in other directions should be selected; if the measured is a multi-dimensional vector, the smaller the cross sensitivity of the sensor, the better.

2. Resolution The resolution of the angle sensor means that a small change in the shaft can make the output electrical signal give the smallest electrical signal that can be distinguished and detected. The high resolution of the angle sensor can achieve high-precision measurement. However, high resolution does not necessarily require high accuracy of the sensor, because there are many factors such as the linearity of the sensitive element, temperature, hysteresis, reset, use environment, etc., which will affect the overall accuracy of the angle sensor.

3. Linearity range (also called nonlinear deviation) The linear range of an angle sensor refers to the range where the output is proportional to the input. In theory, the sensitivity remains constant within this range. The wider the linear range of the sensor, the larger the measuring range, and a certain measurement accuracy can be guaranteed. When selecting a sensor, when the type of sensor is determined, it is first necessary to see whether its range meets the requirements. But in fact, no sensor can guarantee absolute linearity, and its linearity is also relative. When the required measurement accuracy is relatively low, within a certain range, the sensor with less nonlinear error can be approximately regarded as linear, which will bring great convenience to the measurement. The method of describing the linearity deviation often uses the least square method. Nowadays, independent linearity is used in many occasions.

4. Frequency response characteristics The frequency response characteristics of the angle sensor determine the frequency range to be measured, and the measurement conditions must be kept undistorted within the allowable frequency range. In fact, the response of the sensor always has a fixed delay. I hope that the shorter the delay time, the better . For smart angle sensors that only use microprocessors and ADCs or DACs, the response frequency of the selected device often determines the response frequency of the angle sensor. The frequency response of the sensor is high, the signal frequency range that can be measured is wide, and due to the influence of the structural characteristics, the inertia of the mechanical system is larger, and the frequency of the measurable signal is lower due to the low frequency sensor. In dynamic measurement, the response characteristics should be based on the characteristics of the signal (steady state, transient state, random, etc.) to avoid over-fire errors. 4. Reset repeatability: The reset characteristics of the angle sensor include the deviation of the output electrical signal when the angle sensor changes to the same position multiple times in one direction; it also includes the deviation of the output electrical signal when the sensor increases in one direction and the reverse return stroke reaches the same position. This indicator shows the degree of accurate position measurement of the angle sensor. The DWQT angle sensor of okplazas.com tested by the New York City Metrology Institute gives a one-way approach and reverse reset measurement, a measurement report of less than one millivolt.

5. Stability The ability of the sensor to keep its performance unchanged after a period of use is called stability. In addition to the structure of the sensor itself, the factors affecting the long-term stability of the sensor are mainly the use environment of the sensor. Therefore, to make the sensor have good stability, the sensor must have strong environmental adaptability. Before selecting an angle sensor, investigate its use environment, and select the appropriate sensor according to the specific use environment, or take appropriate measures to reduce the environmental impact. 6. The accuracy of the angle sensor: The accuracy of the sensor is a comprehensive index, which covers the comprehensive detection effects of linearity, reset accuracy, temperature coefficient, frequency response error, and environmental suitability. It calibrates the maximum deviation between the measurement result and the true value of the angle sensor within a given measurement range. There are two ways to describe the accuracy of a sensor: relative error and absolute error: relative error represents the maximum deviation value measured in a given range and the percentage value of the range range. The maximum deviation value can appear at any position within the range. , Generally expressed as 1%, 0.5%, 0.1%, etc. Absolute error means that no point within the given range can exceed the given maximum deviation value, such as 1°, 0.2°. The absolute error is generally more demanding, and manufacturers are generally unwilling to accept it. If this condition is forced, it is generally a high-precision measurement. Product prices will increase several times. The above is a reference for electrical performance selection provided by okplazas.com for angle sensor selectors who have been committed to the innovation and development of magnetic sensors for 30 years. okplazas.com has condensed hundreds of application cases, can provide users with feasible angle sensor selection schemes, consulting guidance, special product customization, and provide cost-effective, timely delivery, reliable products, and enjoy a complete after-sales service system stand by