
Configuration and Use Manual
183
Maintenance and Troubleshooting
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3. Check the core processor LED against the conditions described in Table 15-7.
4. To return to normal operation, replace the lid.
Note: When reassembling the meter components, be sure to grease all O-rings.
15.17.2
Core processor resistance test
To perform the core processor resistance test:
1. Remove the core processor lid.
2. Disconnect the 4-wire cable between the core processor and the Model 3711.
3. Measure the resistance between core processor terminals 3 and 4 (RS-485A and RS-485B).
See Figure 15-2. Resistance should be 40 k
Ω
to 50 k
Ω
.
4. Measure the resistance between core processor terminals 2 and 3 (VDC– and RS-485A).
Resistance should be 20 k
Ω
to 25 k
Ω
.
5. Measure the resistance between core processor terminals 2 and 4 (VDC– and RS-485B).
Resistance should be 20 k
Ω
to 25 k
Ω
.
6. If any resistance measurements are lower than specified, the core processor may not be able to
communicate with the Model 3711. Contact Micro Motion (see Section 1.8).
Table 15-7
Core processor LED behavior, meter conditions, and remedies
LED behavior
Condition
Possible remedy
1 flash per second (ON
25%, OFF 75%)
Normal operation
No action required.
1 flash per second (ON
75%, OFF 25%)
Slug flow
Solid ON
Zero or calibration in
progress
If calibration is in progress, no action required. If no calibration is in
progress, contact Micro Motion. See Section 1.8.
Core processor
receiving between 11.5
and 5 volts
Verify power supply wiring
.
3 rapid flashes,
followed by pause
Sensor not recognized
Check wiring between Model 3711 and sensor. See Section 15.15.2
Improper configuration
Check sensor characterization parameters. See Section 5.5.1.
Broken pin between
sensor and core
processor
Contact Micro Motion. See Section 1.8.
4 flashes per second
Fault condition
Check alarm status.
OFF
Core processor
receiving less than 5
volts
• Verify power supply wiring
.
See Section 15.15.1.
• If Model 3711 display is active, device is receiving power. Check
voltage across terminals 1 (VDC+) and 2 (VDC–) in core processor.
Normal reading is approximately 14 VDC. If reading is normal,
internal core processor failure is possible. Contact Micro Motion. If
reading is 0, internal device failure is possible. Contact Micro Motion.
If reading is less than 1 VDC, verify power supply wiring to core
processor. Wires may be switched. See Section 15.15.1.
• If Model 3711 display is not lit, device is not receiving power. Check
power supply. See Section 15.15.1. If power supply is operational,
internal device failure is possible. Contact Micro Motion. See
Section 1.8.
Core processor
internal failure
Contact Micro Motion. See Section 1.8.
Summary of Contents for Micro Motion 3711
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