Excessive (saturated) drive gain
Table 15-1: Possible causes and recommended actions for excessive (saturated) drive gain
Possible cause Recommended actions
Bent sensor tube Check the pickoff voltages (see Check the pickoff voltage). If either of them are close to
zero (but neither is zero), the sensor tubes may be bent. The sensor will need to be
replaced.
Cracked sensor tube Replace the sensor.
Flow rate out of range Ensure that the flow rate is within sensor limits.
Open drive or pickoff
sensor coil
Contact customer support.
Over-pressurized tubes Contact customer support.
Plugged sensor tube Check the pickoff voltages (see Check the pickoff voltage). If either of them are close to
zero (but neither is zero), plugged tubes may be the source of your problem. Purge the
tubes. In extreme cases, you may need to replace the sensor.
Sensor case full
of process fluid
Replace the sensor.
Sensor imbalance Contact customer support.
Sensor tubes
not completely full
Correct process conditions so that the sensor tubes are full.
Two-phase flow Check for two-phase flow. See Check for two-phase flow (slug flow).
Vibrating element
not free to vibrate
Ensure that the vibrating element is free to vibrate.
Erratic drive gain
Table 15-2: Possible causes and recommended actions for erratic drive gain
Possible cause Recommended actions
Foreign material
caught in sensor tubes
• Purge the sensor tubes.
• Replace the sensor.
15.30 Checking process variables
Micro Motion suggests that you make a record of the process variables listed below, under normal operating
conditions. This list will help you recognize when the process variables are usually high or low.
• Flow rate
• Density
• Temperature
• Tube frequency
• Pickoff voltage
• Drive gain
Troubleshooting Configuration and Use Manual
April 2019 MMI-20048166
198 Micro Motion 4200 Transmitters
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