177
Reference Manual
00809-0300-4750, Rev CA
March 2016
9.6.2
Uninstalled sensor tests
Sensor troubleshooting can also be performed on an uninstalled sensor. If test results from
installed sensor tests are inconclusive, the next step is remove the sensor and perform the
tests outlined in
. Take measurements from the feed-through pins and directly on
the electrode head inside the sensor. The measurement electrodes, 18 and 19, are on
opposite sides in the inside diameter of the sensor. If applicable, the third process reference
electrode is between the two measurement electrodes.
The expected values in the test below assume the measurements have been taken directly
at the pins.
Table 9-9. Uninstalled Sensor Tests and Expected Values
Test
Sensor
location
Required
equipment
Measuring at
connections
Expected
value
Potential cause
Corrective action
A. Terminal to
front electrode
Uninstalled
Multimeter
18 and
electrode 18
(1)
1.
When the connection head is in the vertical upright position and the flow arrow (see
) on the connection head flange points to
the right, the front of the meter will be facing towards you. Electrode 18 is on the front of the meter. If you cannot determine the front of the meter,
measure both electrodes. One electrode should result in an open reading, while the other electrode should be less than 1
.
≤
1
Ω
•Shorted electrode
•Open electrode
•Coated electrode
•Replace sensor
•Remove coating
from sensor wall
B. Terminal to
back electrode
Uninstalled
Multimeter
19 and
electrode 19
≤
1
Ω
•Shorted electrode
•Open electrode
•Coated electrode
•Replace sensor
•Remove coating
from sensor wall
C. Terminal to
reference
electrode
Uninstalled
Multimeter
17 and process
reference
electrode
(2)
2.
Only valid if the sensor has a process reference electrode.
≤
0.3
Ω
•Shorted electrode
•Open electrode
•Coated electrode
•Replace sensor
•Remove coating
from sensor wall
D. Terminal to
case ground
Uninstalled
Multimeter
17 and safety
ground
≤
0.3
Ω
•Moisture in
terminal block
•Leaky electrode
•Process behind
liner
•Clean terminal
block
•Replace terminal
block
•Replace sensor
E. Electrode to
electrode
shield
Uninstalled
Multimeter
18 and 17
∞Ω
(<1 nS)
•Shorted electrode
•Leaky electrode
•Moisture in
terminal block
•Replace sensor
•Clean terminal
block
•Replace terminal
block
19 and 17
∞Ω
(<1 nS)
•Shorted electrode
•Leaky electrode
•Moisture in
terminal block
•Replace sensor
•Clean terminal
block
•Replace terminal
block
F. Electrode
shield to coil
Uninstalled
Multimeter
17 and 1
∞Ω
(<1 nS)
•Process in coil
housing
•Moisture in
terminal block
•Replace sensor
•Clean terminal
block
•Replace terminal
block
Ω
Summary of Contents for Rosemount 8750W
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