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232 Micro Motion
®
Series 3000 MVD Transmitters and Controllers
Diagnostics and Troubleshooting
22.18.5 Low pickoff voltage
Low pickoff voltage can be caused by several problems. See Table 22-13.
22.19 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
flowmeter conditions. See Table 22-14.
• If an A026 alarm is present, you can perform the core processor resistance test to check for a
damaged core processor.
22.19.1 Checking the core processor LED
To check the core processor LED:
1. Maintain power to the transmitter.
2. Remove the core processor lid. The core processor is instrinsically safe and can be opened in
all environments. Do not disconnect the 4-wire cable between the core processor and the
transmitter.
3. Check the core processor LED against the conditions described in Table 22-14 (standard core
processor) or Table 22-15 (enhanced core processor).
4. To return to normal operation, replace the lid.
Note: When reassembling the meter components, be sure to grease all O-rings.
Table 22-12 Erratic drive gain causes and remedies
Cause Possible remedy
Wrong K1 characterization constant for sensor Re-enter the K1 characterization constant. See
Section 7.3.3.
Polarity of pick-off reversed or polarity of drive reversed Contact Micro Motion.
Slug flow Verify flow tubes are completely full of process fluid.
Foreign material caught in flow tubes Purge flow tubes.
Table 22-13 Low pickoff voltage causes and remedies
Cause Possible remedy
Faulty wiring runs between the sensor and core processor Verify wiring. See Section 22.11.2.
Process flow rate beyond the limits of the sensor Verify that the process flow rate is not out of range of the
sensor.
Slug flow Verify flow tubes are completely full of process fluid.
No tube vibration in sensor Check for plugging.
Verify power to transmitter.
Ensure sensor is free to vibrate (no mechanical binding).
Verify wiring. See Section 22.11.2.
Test coils at sensor. See Section 22.20.
Moisture in the sensor electronics Eliminate the moisture in the sensor electronics.
The sensor is damaged Contact Micro Motion.