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234 Micro Motion
®
Series 3000 MVD Transmitters and Controllers
Diagnostics and Troubleshooting
22.19.2 Core processor resistance test (standard core processor only)
Note: Perform this test only if an A026 alarm is present.
To perform the core processor resistance test:
1. Power down the transmitter.
2. Remove the core processor lid.
3. Disconnect the 4-wire cable between the core processor and the transmitter.
4. Measure the resistance between core processor terminals 3 and 4 (RS-485/A and RS-485/B).
See Figure 22-6. Resistance should be 40 kΩ to 50 kΩ.
5. Measure the resistance between core processor terminals 2 and 3 (VDC– and RS-485/A).
Resistance should be 20 kΩ to 25 kΩ.
6. Measure the resistance between core processor terminals 2 and 4 (VDC– and RS-485/B).
Resistance should be 20 kΩ to 25 kΩ.
7. If any resistance measurements are lower than specified, the core processor may not be able to
communicate with a transmitter or a remote host. Contact Micro Motion customer service.
8. To return to normal operation:
a. Reconnect the 4-wire cable between the core processor and the transmitter.
b. Replace the core processor lid.
Note: When reassembling the meter components, be sure to grease all O-rings.
Flashing red (50% on,
50% off, skips every
4th)
Sensor failed Contact Micro Motion.
OFF Core processor
receiving less than 5
volts
• Verify power supply wiring to core processor
.
• If transmitter display is lit, transmitter is receiving power. Check
voltage across terminals 1 (VDC+) and 2 (VDC–) in core processor.
If reading is less than 1 VDC, verify power supply wiring to core
processor. Wires may be switched. See Section 22.11. Otherwise,
contact Micro Motion.
• If transmitter display is not lit, transmitter is not receiving power.
Check power supply. See Section 22.11. If power supply is
operational, internal transmitter, display, or LED failure is possible.
Contact Micro Motion.
Core processor
internal failure
Contact Micro Motion.
Table 22-15 Enhanced core processor LED behavior, flowmeter conditions, and remedies continued
LED behavior Condition Possible remedy