Low Pickoff Voltage; 15.17 Checking The Core Processor; Checking The Core Processor Led - Emerson Micro Motion 3711 Configuration And Use Manual

Maintenance and Troubleshooting
Table 15-5 Drive gain problems, causes, and remedies
Cause
Drive board or module failure, cracked flow tube,
or sensor imbalance
Mechanical binding at sensor
Open drive or left pickoff sensor pin
Flow rate out of range
Wrong K1 and FCF characterization constants
for sensor
Incorrect sensor type configured
Polarity of pick-off reversed or polarity of drive
reversed
15.16.3

Low pickoff voltage

Low pickoff voltage can be caused by several problems. See Table 15-6.
Table 15-6 Low pickoff voltage causes and remedies
Cause
Faulty wiring runs between the sensor and core processor
Process flow rate beyond the limits of the sensor
Slug flow
No tube vibration in sensor
Moisture in the sensor electronics
The sensor is damaged

15.17 Checking the core processor

Two core processor procedures are available:
• You can check the core processor LED. The core processor has an LED that indicates different
meter conditions. See Table 15-7.
• You can perform the core processor resistance test to check for a damaged core processor.
15.17.1

Checking the core processor LED

To check the core processor LED:
1. Maintain power to the Model 3711.
2. Remove the core processor lid. The core processor is instrinsically safe and can be opened in
all environments.
182
Possible remedy
Contact Micro Motion. See Section 1.8.
Ensure sensor is free to vibrate.
Contact Micro Motion. See Section 1.8.
Ensure that flow rate is within sensor limits.
Re-enter the K1 and FCF characterization constants. See
Section 5.5.1.
Verify sensor characterization. See Section 5.5.1.
Contact Micro Motion. See Section 1.8.
Possible remedy
Verify wiring. Refer to Appendix A for diagrams, and see
your transmitter installation manual.
Verify that the process flow rate is not out of range of the
sensor.
See Section 15.12.
Check for plugging.
Ensure sensor is free to vibrate (no mechanical binding).
Verify wiring.
Test pins at sensor. See Section 15.17.
Eliminate the moisture in the sensor electronics.
Contact Micro Motion. See Section 1.8.
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Micro Motion Model 3711 Gas Flow Computers