Troubleshooting Guide
Sensor circuits
5 - 6 SKF Multilog On-Line System IMx-S
User Manual – Revision S
NO: Problem appears to be related to the signal loop connected to the IMx input.
Continue with further checks on the source equipment and the integrity of the
interconnecting cables.
YES: Problem appears to be related to the IMx (hardware, installation or
configuration) or to a compatibility issue with the sensor. If on rechecking the
aspects advised above, no reason for the measurement error is found, contact
TSG for advice.
Checking digital channels
Be aware that digital inputs 1 to 4 are configurable for different types of sensors, via DIP
switch settings, whilst digital inputs 5 to 8 have fixed characteristics and provide no
sensor power. Refer to
Digital Inputs, for further detail.
Effective troubleshooting for tacho signals will likely require a handheld/portable
oscilloscope or DMM with oscilloscope capabilities, a battery powered unit being
preferred. It will be hindered if the IMx-S cannot be accessed when the speed signal is
active.
1. Where applicable, check the sensor installation, the security of the mounting, the
gap to the target and the differential gap between target and no target, conditions.
Ensure these are acceptable for the sensor being used and that the sensor output
will cross the trigger threshold for the particular IMx-S digital channel being used.
2. Identify the digital input terminals where the channel in question is connected to
the IMx-S. Confirm that the wiring is correct for the sensor type in use and where
applicable, the DIP switch settings are correct.
3. Is sensor power, supposed to be, supplied by the IMx-S?
NO: Skip to step 4, dynamic, oscilloscope checks
YES: The sensor must use a digital channel in the range 1 to 4. Measure the DC
voltage between the A (power) and 0 (common) terminals using a digital
voltmeter.
a. Is the measured voltage approximately 24 V DC, as expected?
YES: Skip to step
4, dynamic, oscilloscope checks
NO: Disconnect the sensor cable from the A (power) terminal and recheck the
voltage across the A and 0 terminals.
b. Is the measured voltage now around 24 V DC as expected?
YES: Double check that the sensor is compatible, especially that the sensor current
requirement is within the capability of the IMx-S.
To confirm a sensor/cable fault: if available try substituting an alternative sensor or
confirm that in a known working installation the same type of sensor does not
load the IM seso poe i this a.
NO: The test suggests a fault in the IMx-S, contact TSG for further advice.
4. When a speed signal is expected to be present, observe the signal at the B (signal)
and 0 (common) terminals on an oscilloscope. Is the expected pulsed waveform
present?
NO: Cable, sensor or installation issue. If practicable replace the sensor by a signal
source to test the measurement chain, excluding sensor/target, and to verify
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