Strain Gauge Torque Sensor Structure
It mainly includes four parts:
elastic shaft, measuring bridge, instrument amplifier and interface circuit.
As the main component of the sensor, the design of the elastic shaft is crucial. At the positions of 45 degrees and 135 degrees, the elastic shaft will experience the maximum compressive stress and tensile stress, which makes the principal stress and shear stress equal, which can be calculated according to τ=σ/Wp.
The measuring bridge usually consists of four strain gauges to form a differential full bridge to improve the linearity and stability of the signal. When the resistance of the strain gauge changes, the output voltage of the bridge is proportional to the applied torque.
The resistance value of the strain gauge is R1=R2=R3=R4=R0. According to the working principle of the bridge, the relationship between the output voltage and the torque can be obtained. In order to improve the measurement accuracy, the power supply voltage of the bridge, the sensitivity coefficient S of the resistance strain gauge and the amplification factor K of the amplifier circuit all need to be carefully designed.
The amplifier circuit usually uses an instrument amplifier to ensure high accuracy and low noise.
Car Strain Gauge Torque Sensor Detection Steps:
1. Measure the voltage on the wheel speed sensor plug. Because there are a lot of electronic components inside the magnetoresistive sensor that need a power supply and grounding. If the power supply voltage is measured. It can be judged that the sensor is a magnetoresistive torque speed sensor.
2. If there is no voltage, but there is a 100-1000 ohm resistance, it is a magnetoelectric torque speed sensor.
3. Measure the sensor signal. The magnetoresistive wheel speed sensor outputs a square wave pulse signal, which has strong anti-interference. Use the hook of the oscilloscope probe to clamp the signal line, the black clip to clamp the car body, and turn the signal disk to see a 0.5V-1.5V square wave signal waveform.
4. The multimeter measurement method is as follows: black test pen, red test pen connected to the signal line, turn the signal disk by hand, and the voltage on the multimeter display will fluctuate from 0.5V to 1.5V, which is normal. If there is no signal output, you should check: signal disk (whether the signal is very dirty), sensor gap, sensor itself, etc.
5. Sensor data stream comparison method: enter the ABS module to read the sensor data stream, start the car for a road test, and observe the sensor data stream and compare it with the other three wheel speed sensors. This method can be used to detect occasional sensor failures.
