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Reference Manual
00809-0100-4444, Rev AC
Section 9: Troubleshooting
January 2015
Troubleshooting
9.6.4 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 Tab le 9 -9 . 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 Figure 2-4 on page 12) 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 0.3
.
1
• 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)
1
• 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
• 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
•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
(<1 nS)
• Shorted electrode
• Leaky electrode
•Moisture in
terminal block
•Replace sensor
• Clean terminal
block
•Replace terminal
block
19 and 17
(<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
(<1 nS)
• Process in coil
housing
•Moisture in
terminal block
•Replace sensor
• Clean terminal
block
•Replace terminal
block