Instruction manual

Using Modbus
®
Protocol with Micro Motion
®
Transmitters 241
Troubleshooting continued
Configuration Record Index
Output and Transmitter
Testing
Troubleshooting
Modbus Mapping
Assignments
Message Framing
Reference
transmitter terminals that are listed in Table 23-6, page 237, then
use a DMM to measure resistance between wire pairs.
• If open or short circuits are found, or if measured resistance
values are outside the ranges listed in
Table 23-8, page 238, the
sensor cable might be faulty. See Table 23-10, page 239.
• If faulty sensor cable is not indicated, go to step 4.
4. Before reconnecting wiring at the transmitter terminals, measure
resistance between wire pairs at the sensor junction box. See
Table 23-10.
5. If troubleshooting fails to reveal why diagnostic codes have switched
ON, phone the Micro Motion Customer Service Department. (See
page 247 or the back cover for phone numbers.)
Version 3 RFT9739 transmitter
If a Version 3 RFT9739 transmitter indicates sensor failure or overrange
conditions and produces fault outputs:
1. Read register pairs 20285-20286 to 20291-20292, as listed in
Table 23-5, page 236.
2. Compare the returned values with the values described in Table 23-
5 and Table 23-7, page 237:
• If the drive gain is unstable, see Table 23-9, page 238.
• If the value for the left or right pickoff does not equal the
appropriate value from
Table 23-7, based on the sensor flow tube
frequency, go to step 3.
3. Disconnect sensor wiring from the intrinsically safe transmitter
terminals that are listed in
Table 23-6, page 237, then use a DMM to
measure resistance between wire pairs.
• If open or short circuits are found, or if measured resistance
values are outside the ranges listed in
Table 23-8, page 238, the
sensor cable might be faulty. See Table 23-10, page 239.
• If faulty sensor cable is not indicated, go to step 4.
4. Before reconnecting wiring at the transmitter terminals, measure
resistance between wire pairs at the sensor junction box. See
Table 23-10.
5. If troubleshooting fails to reveal why diagnostic codes have switched
ON, phone the Micro Motion Customer Service Department. (See
page 247 or the back cover for phone numbers.)
Version 2 RFT9739 transmitter
If the Version 2 RFT9739 transmitter indicates sensor failure or
overrange conditions and produces fault outputs, use a digital
multimeter (DMM) or other reference device to measure resistance
across wire pairs or test points. Refer to the transmitter manual for test
procedures, expected values, and suggested actions.