SKF Multilog IMx-S Series User Manual page 29

4. Is the voltage close to the open circuit voltage?
YES: There is an open circuit in the cable or the sensor is damaged. Skip to step 5.
NO: If the voltage appears to be neither within the normal working range, close to
Remaining faults can be due to a damaged sensor or a damaged IMx-S input circuit. First,
disconnect one pole of the sensor cable and measure the open circuit voltage to verify
whether the open circuit voltage is normal (about 24 V DC). If it is normal, then the fault
is probably in the sensor, otherwise the fault is likely in the IMx-S.
5. Disconnect the connector from the sensor and short circuit the pins in the sensor
contact, then re-measure the voltage on the IMx-S terminal block. Did the voltage
sink to close to zero (<0,5 V)?
NO: There is an open circuit in the cable. Repair/replace the cabling.
YES: There is an internal open circuit in the sensor or there is a bad/oxidised
Checking eddy current probe inputs
Like troubleshooting a 2-wire accelerometer, the checking of eddy current probe inputs
includes confirming the presence of a return signal DC offset in an acceptable or
expected range. In this case however, the sensors are 3-wire, so have a separate wire for
the power supply, and that signal return DC is related to the gap between the probe and
the target or shaft.
1. Identify the input terminals where the channel in question is connected to the IMx-S
and first measure the sensor power supply voltage between Pwr and B at the
terminal block, using a digital voltmeter.
2. Is the measured voltage as expected? For an eddy current probe system this should
be close to -24 V DC, a significantly lower voltage would indicate a fault.
Yes: Skip to step 3.
No: Now remove the sensor wiring from the Pwr terminal and recheck.
a. Did the fault remain?
SKF Multilog On-Line System IMx-S
User Manual – Revision S
NO: The sensor is defective. Replace the sensor.
YES: The sensor cable (or contact/connector) has a short circuit and requires
repair/replacement.
zero nor close to the open circuit voltage, then the fault is an unusual one.
First, recheck that the DCV measurement was correctly carried out, then
contact TSG for advice.
contact. First, try cleaning the contact before replacing the sensor connector
and checking again.
NO: The sensor circuit appears to be excessively loading the power supply.
Check the sensor circuit cabling for the presence of a short, a similar
measurement with the sensor wiring disconnected at the driver end can be
used to indicate whether the fault lies with the cabling or the driver. Repair
or replace as required.
YES: Check first the configuration settings for this channel, especially the DIP
switches. If all appears as expected, the fault may be with the IMx-S device,
contact TSG for advice and further information.
Troubleshooting Guide
Sensor circuits
5 - 3