Troubleshooting
65
results due to a battery-like effect when dissimilar metals
contact conductive liquids.
CAUTION: Sensing element is intrinsically safe. Therefore,
when using this product, it is recommended that all service
activity comply with appropriate guidelines.
Remove sensing element from vessel to a safe area. Test outlined
in steps 1 and 2 can be performed in a metal test vessel,
grounded to the sensor, and filled with high conductivity water.
Depending on locality, tap water may not be suitable. If low
conductivity water is used, a spoonful of table salt can be added
which will increase the conductivity.
In the following tests, if it is not possible to raise or lower the
level in vessel, the sensing element may be suspended in a metal
pipe or other container that is filled with conductive water (see
above note) and connected to grounded sensing element condulet.
If container is not metallic, then a ground wire or rod is needed
to be placed into the water and referenced to sensing element
condulet or mounting devices.
Testing the Sensing Element - Step 1 (Figure 5-3)
With the material below the sensor, and the coaxial cable
disconnected at the sensing element, measure the resistance
from the sensing element center connector to ground connector
(or condulet). The ohmmeter should be set to R x 10000 scale.
The reading should be infinite (open circuit). Readings of less
than one meg-ohm indicate excessive electrical leakage, probably
due to product leakage or condensation in the packing seal or
condulet. Record the resistance value measured. Contact the
Service department for recommended repairs.
Testing the Sensing Element - Step 2
(Figure 5-4 fully insulated sensing elements only)
Raise the level in the vessel to cover as much of the sensor as
possible. Repeat the measurement made in step 1. Readings of
1 meg-ohm or less indicate a pinhole or crack in the sensing
element insulation. Failed insulation is not field repairable.
Consult the Service department for further assistance.
If there is water or other conductive material in the conduit (ie.:
Excessive wire lube) it can change the electrical properties of
the coax cable and cause the system to perform poorly. Moisture
in the conduit may not be detected by the following test. The
only sure way is to inspect the coax and associated conduit for
trapped water.
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