Emerson Micro Motion LNG Series, Configuration And Use Manual

Page: 90 / 100

There should be no open circuits, that is, no infinite resistance readings. The left
pickoff and right pickoff readings should be the same or very close (
±5
Ω
. If there
are any unusual readings, repeat the coil resistance tests at the sensor junction box
to eliminate the possibility of faulty cable. The readings for each coil pair should
match at both ends.
4. Test the terminals in the sensor junction box for shorts to case.
a. Leave the terminal blocks disconnected.
b. Remove the lid of the junction box.
c. Testing one terminal at a time, place a DMM lead on the terminal and the other
lead on the sensor case.
With the DMM set to its highest range, there should be infinite resistance on
each lead. If there is any resistance at all, there is a short to case.
5. Test the resistance of junction box terminal pairs.
a. Test the brown terminal against all other terminals except the red one.
b. Test the red terminal against all other terminals except the brown one.
c. Test the green terminal against all other terminals except the white one.
d. Test the white terminal against all other terminals except the green one.
e. Test the blue terminal against all other terminals except the gray one.
f. Test the gray terminal against all other terminals except the blue one.
g. Test the orange terminal against all other terminals except the yellow and violet
ones.
h. Test the yellow terminal against all other terminals except the orange and violet
ones.
i. Test the violet terminal against all other terminals except the yellow and orange
ones.
There should be infinite resistance for each pair. If there is any resistance at all, there
is a short between terminals.
Postrequisites
To return to normal operation:
1. Plug the terminal blocks into the terminal board.
2. Replace the lid on the sensor junction box.
Important
When reassembling the meter components, be sure to grease all O-rings.
Troubleshooting
84 Micro Motion ® LNG Series Meters