Emerson Micro Motion LNG Series, Configuration And Use Manual

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To know whether your pickoff voltage is unusually low, you must collect pickoff voltage
data during the problem condition and compare it to pickoff voltage data from a period of
normal operation.
Possible causes and recommended actions for low pickoff voltage Table 10-7:
Possible cause Recommended actions
Faulty wiring runs between the sensor
and transmitter Verify wiring between sensor and transmitter.
Process flow rate beyond the limits of
the sensor Verify that the process flow rate is not out of range of the
sensor.
The vibrating element is not vibrating • Check for plugging or deposition.
• Ensure that the vibrating element is free to vibrate
(no mechanical binding).
• Verify wiring.
• Test coils at sensor. See Section 10.12.1 .
Moisture in the sensor electronics Eliminate the moisture in the sensor electronics.
The sensor is damaged, or sensor mag-
nets may have become demagnetized Replace the sensor.
10.11.1 Collect pickoff voltage data
Pickoff voltage data can be used to diagnose a variety of process and equipment
conditions. Collect pickoff voltage data from a period of normal operation, and use this
data as a baseline for troubleshooting.
Procedure
1. Navigate to the pickoff voltage data.
2. Observe and record data for both the left pickoff and the right pickoff, over an
appropriate period of time, under a variety of process conditions.
10.12 Check for internal electrical problems
Shorts between sensor terminals or between the sensor terminals and the sensor case can
cause the sensor to stop working.
Possible causes and recommended actions for electrical shorts Table 10-8:
Possible cause Recommended action
Moisture inside the sensor junction
box Ensure that the junction box is dry and no corrosion is
present.
Liquid or moisture inside the sensor
case Contact Micro Motion.
Troubleshooting
82 Micro Motion ® LNG Series Meters