Strain gauge pressure sensor is usually four-wire system (excluding shielded wire), usually red, black, green and white four wires, in which red and black are positive and negative power supply (excitation), green and white are positive and negative signal (output). Use a multi-meter electrical block, measure the impedance between the red line and the black line and the impedance of the green line and the white line, see whether the impedance parameters in the symbol parameter table, if the measurement results of infinite impedance, indicating that the pressure sensor bridge is open, if the impedance is zero, indicating that the pressure sensor bridge short circuit, both cases indicate that the pressure sensor has been broken, need to send back to the manufacturer repair.

 

If the measured impedance is normal, the following tests can be carried out. Power the pressure sensor (5-15VDC, 10V is preferred), measure the millivolt between the green and white lines with a multi-meter millivolt stop, and measure the millivolt between the green and white lines with no load first. If the millivolt value is too large, it indicates that the pressure sensor is overloaded (premise: Pressure sensor has zero adjustment before delivery), if the millivolt value is very negative, it indicates that the sensor is pulling overload. If there is no change in the output of millivolt value at the force point of the sensor when pressed, it indicates that the pressure sensor is damaged. Pressure sensor due to overload caused by serious deformation of the elastomer usually cannot be repaired, can only replace the sensor.

 

After the above two tests, we can basically judge whether the pressure sensor is damaged. If the above two test results are normal, the supporting instrument or transmitter display or signal output is not normal, we have to check the supporting instrument or transmitter.