The torque sensor is a precision measuring instrument for measuring various torques, speeds and mechanical power. It has a wide range of applications. In alumina production enterprises, it is mainly used to detect the torque of the driving device of the settling tank rake machine. It is a very important measurement and protection parameter of the settling tank rake machine. To ensure the safe operation of the settling tank rake machine, the DCS sends an alarm signal when the torque is abnormal, and the DCS interlocks to protect the rake machine to stop running when the protection setting value is reached. In the actual production process, the torque sensor itself often causes false alarms and malfunctions of the equipment due to inaccurate measurements, thereby causing unnecessary equipment failures and causing great impact on production. How to judge the performance of the torque sensor? This article introduces the method of using hanging code loading to detect and judge the performance of the torque sensor.
1  Measurement principle of torque sensor
The more mature detection method for torque measurement is strain gauge electrical measurement technology, which has the advantages of high accuracy, fast frequency response, good reliability and long life. The measurement principle of the strain gauge torque sensor: Using the strain gauge electrical measurement technology, the strain gauge is attached to the elastic shaft to form a measuring bridge. When the elastic shaft is slightly deformed by torque, the resistance value of the bridge arm changes. The change in the resistance of the strain bridge arm is converted into a change in the voltage signal, thereby measuring the torque.
2  Torque sensor detection device
2.1  Detection device

Angle steel, channel steel and other steel materials are welded to make a steel detection bracket. A channel steel is fixed on the bracket as a fixed plate. Two holes with a diameter of 6mm are opened at both ends of the fixed plate, which are used to fix the counterweight and torque sensor respectively. The counterweight plays a balancing role when the torque sensor is detected to prevent the detection device from tipping over due to uneven force. The other end of the sensor is connected to the weight tray, and the tray can be loaded with detection weights. The weights use 20kgM1 standard weights.

3.Determination of the maximum allowable error of the torque sensor
The maximum sensor error of the torque sensor during loading and unloading in the test data is -0.1%, which is not greater than the maximum allowable error ±0.5%.
The maximum allowable error of the torque sensor is determined to be qualified.
Determination of repeatability error
The torque sensor applies the same load 3 times in the same direction, and the maximum difference of the 3 measured values is 0.0105mA. The repeatability error is the maximum difference divided by the output range of the torque sensor multiplied by 100%.
That is, 0.0105/16×100%=0.1%, which is not greater than the maximum allowable error ±0.2%. The repeatability error of the torque sensor is determined to be qualified.
Determination of nonlinear error
The maximum difference between the theoretical output value of each test point of the torque sensor and the 3 measured values of the point is 0.0138mA. The nonlinear error is the maximum difference divided by the output range of the torque sensor multiplied by 100%.
That is, 0.0138/16×100%=0.1%, which is not greater than the maximum allowable error ±0.2%, and the nonlinear error of the torque sensor is judged to be qualified.
Hysteresis error judgment The maximum difference of the measured values of each load point during the loading and unloading process of the torque sensor is 0.001mA. The hysteresis error is the maximum difference 0.001 divided by the output range of the torque sensor multiplied by 100%. That is, 0.001/16×100%=0.0%, which is not greater than the maximum allowable error ±0.2%, and the hysteresis error of the torque sensor is judged to be qualified.
In summary, the maximum allowable error, repeatability error, nonlinear error and hysteresis error of the torque sensor are all qualified. Finally, it is judged that the performance of the torque sensor meets the requirements and the test result is qualified.
The performance test of the torque sensor using the weight loading method can determine whether the torque sensor has good performance and replace the unqualified torque sensor in advance, which can avoid unnecessary production accidents caused by the torque sensor device error. It is one of the important means to ensure the accuracy of torque measurement. In addition, the performance test of the torque sensor using the weight loading method is practical and simple, with strong practical operability, and has achieved good results in practice.