INSTALLATION AND OPERATING INSTRUCTIONS
Troubleshooting
42 (63)
SKF Multilog On-line System IMx-8/IMx-8Plus
User Manual
Revision E
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 IMx sensor power in this way.
NO: The test suggests a fault in the IMx device, contact TSG for
further advice.
4. When a speed signal is expected to be present, observe the signal at the D
(digital) and G (ground) 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 most of the measurement chain (excluding
sensor/target) and to verify the cable integrity.
YES: Verify that the signal has an appropriate voltage range and pulse height
to allow the IMx to trigger, refer
. Check the software is correctly
configured for this digital input. If no root cause is identified, contact TSG for
further advice.
In verifying the signal be sure to also examine it at a sufficiently high sample
rate such that the detail of an individual pulse can be checked. In particular
look for any indication of a ‘double pulse’ where a second trigger occurs
in
quick succession to the first as this would likely cause it to be rejected as
being an invalid speed signal. Where the sensor is powered by the IMx, this
has been known to occur if the sensor initially tries to draw excessive current
on the leading edge of the event, i.e. the maximum peak demand of the
sensor is too high. In such a case the reaction of the IMx power supply
protection circuitry may result in the sensor pulse momentarily dropping
below the trigger threshold before recovering, so generating a double pulse. If
this is suspected, to confirm and correct the situation, power the sensor from
an external source of sufficient capacity.
If a speed channel ‘works’ but gives an incorrect speed, check that the correct
pulses
(number of pulses per rev) have been configured, in the software.
2.9.4 Relay driver outputs
1. Identify which relay driver output of which IMx, is being used for the alarm
under investigation, the expected alarm state and consequently whether it is
expected that the relay coil is being energised or not.
2. Is it expected that the coil be energised?
NO: Skip to step
YES: Measure the DC voltage at the relay coil terminals, using a digital
voltmeter.
a. Is the measured voltage as expected, approximately 24 V DC?
YES: Skip to step
