Perform A 700 Core Processor Resistance Test - Emerson Micro Motion 1500 Configuration And Use Manual

Table 10-9: Enhanced core processor LED states
LED state
OFF
10.29

Perform a 700 core processor resistance test

Note
You can perform a resistance test only on a 700 core processor.
Procedure
1.
2.
3.
4.
5.
Postrequisites
To return to normal operation:
1.
Configuration and Use Manual
Description
Core processor receiving less
than 5 volts
Core processor internal failure
Power down the transmitter.
Remove the core processor lid.
At the core processor, disconnect the 4-wire cable between the core processor and
the transmitter.
Measure the resistance between core processor terminal pairs 3–4, 2–3, and 2–4.
Terminal pair Function
3–4 RS-485/A and RS-485/B
2–3 VDC– and RS-485/A
2–4 VDC– and RS-485/B
If any resistance measurements are lower than specified, the core processor may
not be able to communicate with a transmitter or a remote host. The meter may
need factory service.
Reconnect the 4-wire cable between the core processor and the transmitter.
(continued)
Recommended action
• Verify power supply wiring to core processor.
• If transmitter status LED is lit, transmitter is re-
ceiving 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 switch-
ed.
• If transmitter status LED is not lit, transmitter
is not receiving power. Check power supply. If
power supply is operational, internal transmit-
ter, display, or LED failure is possible – the me-
ter may require factory service.
The meter requires factory service.
Troubleshooting
Expected resistance
40 kΩ to 50 kΩ
20 kΩ to 25 kΩ
20 kΩ to 25 kΩ
153