SKF Multilog IMx-S Series User Manual page 30

Troubleshooting Guide
Sensor circuits
3. Now check the return signal DC bias, between the A and B terminals. As mentioned
the e pe tatio is that this ill a a o di g the p o e/shaft gap, ut fo a i -
a ge
the return voltage consistent with the probe gap?
NO: Skip to step 4.
YES: The sensor circuit appears to be responding as expected. The fault may be with
the IMx-S device or the software configuration, contact TSG for advice and further
information. If the appropriate work permit and machine isolations are in place to
allow the probe itself to be checked
4. Now continue the checks at the eddy current probe, driver. Is the power supply
voltage at the driver close to -24 V DC? Note that the value measured at the driver
can be expected to be a little lower in magnitude than that measured at the IMx-S
terminals, due to voltage drop.
YES: Skip to step 5.
NO: A cable fault, likely an open or high resistance connection on the Pwr or
5. At the eddy current probe driver disconnect the signal wire and check the signal DC
voltage at the driver. Is it consistent with the probe gap?
NO: Skip to step 6.
YES: There is a disparity between the signal seen at the driver and that at the IMx-S
6. The tests carried out so far suggest the eddy current probe system is being powered
correctly but is not generating the expected output. Providing the monitored
machine is isolated and there are permits in place for such work, further possible
checks are as follows:
i. Carefully inspect the probe tip for damage and measure the gap to confirm it is
ii. Change the probe gap and monitor the driver output to check it changes
iii. Changeout driver and/or probe and compare test results.
Checking 4-20 mA channels
In case of unexpected measurement values, check the hardware DIP switch settings are
correct and review the channel configuration especially scale, zero level and choice of
engineering units. Ensure the correct signal type has been chosen at the DIP switches
and that the wiring is appropriately applied, noting particularly the difference between
loop and IMx powered, 4-20 mA, circuits.
5 - 4
easurement can be generally expected to be between -2 and -18 V DC. Is
common lines, is indicated as the power supply does not seem to be reaching
the driver as expected. Repair or replace as required.
terminals. Check for and repair or replace as necessary, an open circuit or poor
connection in the cable signal core. If no cable fault is found recheck the
return signal at the IMx-S but with the signal wire disconnected from the
terminals. Contact TSG for advice and further information, advising them of
the tests undertaken and the findings so far.
in range.
appropriately. Alternatively as a quick function check, insert a screw driver
blade or metallic feeler gauge between probe and shaft, in this case the
magnitude of the output DC should reduce, towards its minimum value.
SKF Multilog On-Line System IMx-S
User Manual – Revision S