Check The Pickoff Voltage - Emerson Micro Motion 4200 Configuration And Use Manual

Configuration and Use Manual
MMI-20048166
Table 15-3: Process variables problems and remedies
Symptom
Temperature reading
significantly different
from process temperature
Temperature reading
slightly different
from process temperature
Unusually high density
reading
Unusually low density
reading
Unusually high tube frequency
Unusually low pickoff voltages
Unusually low pickoff voltages
Unusually high drive gain

15.31 Check the pickoff voltage

If the pickoff voltage readings are unusually low, you may have any of a variety of process or equipment
problems.
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.
Drive gain and pickoff voltage are inversely proportional. As drive gain increases, pickoff voltages decrease
and vice versa.
Table 15-4: Possible causes and recommended actions for low pickoff voltage
Possible cause
Process flow rate beyond the limits of the sensor
Sensor tubes are not vibrating
Moisture in the sensor electronics
The sensor is damaged, or sensor magnets may have
become demagnetized
Configuration and Use Manual
(continued)
Cause
RTD failure
Sensor leaking heat
Plugged flow tube
Incorrect K2 value
Slug flow
Incorrect K2 value
Sensor erosion
Plugged fow tube, corrosion, or
erosion
Several possible causes
Several possible causes
Recommended actions
Verify that the process flow rate is not out of range of the
sensor.
•
•
Eliminate the moisture in the sensor electronics.
Replace the sensor.
Suggested remedy
Check for alarm conditions and follow
troubleshooting procedure for indicated
alarm.
Insulate the sensor.
Check drive gain and tube frequency.
Purge the flow tubes.
Verify characterization. See
meter (if required).
Use standard procedures to check the quality
of the process fluid.
Verify characterization. See
meter (if required).
Contact Micro Motion.
Purge the flow tubes.
See Check the pickoff
See Check the drive
Check for plugging or deposition.
Ensure that the vibrating element is free to vibrate (no
mechanical binding).
Troubleshooting
April 2019
Characterize the
Characterize the
voltage.
gain.
201