Fig.1 Shows permanently installed accelerometers, powered by a vibration monitoring system, being measured using a HS-660 cable checker and bias monitor.
Fig.2 Shows the first troubleshooting step to be taken when the bias voltage is 20V rather than the healthy system bias of 12 VDC.
Fig.3 Shows the second troubleshooting step to be taken if it is confirmed that the connector is tightly connected or if the accelerometer is supplied with an integral cable.
Fig.4 Shows a troubleshooting step if the connector was shown to be tightened correctly. This step confirms or eliminates a cable fault between the junction box and the accelerometer. If the cable is seen to have integrity then the likely fault can be diagnosed as reverse wiring. Very rarely is an open circuit associated with a faulty sensor.
Fig.5 Shows the gradual elimination of possible causes. Here this check can determine loose wires (0V bias) and if the bias checker still shows 20V bias then the likelihood is that the cabling is reverse wired.
Checking the wiring against the colour code on the calibration certificate will show that the likely cause of the 20V bias is reversed wiring.
If the bias checker shows 0V then either the power supply to the sensor is not working or there is a short in the cabling pulling down the supply voltage.
A further test is to use the HS-661 accelerometer simulator. Here we are checking that the sensor is wired to the appropriate channel in the vibration monitoring system and secondly that the alarms are set correctly and the scaling is correct.
Fig.9 Shows the Hansford Sensors vibration monitoring system and the build in bias checking. This eliminates a number of the steps in troubleshooting.