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RNLXX1 - IntelliPoint RF Series User's Manual
4.6
Testing The Sensing Element
Integral electronics, See figure 2-6
Remove Sensing Element Circuit Board and disconnect cable
from circuit board
Remote electronics, See figure 2-7
Disconnect remote cable at the sensing element.
1. With the sensing element in the vessel, verify level is below
the sensing element
2. Use an analog ohmmeter
scale, measure the resistances between each pair of sensing
element connections. See Figure 4-2 & 4-3. Record values
in Table 4.1
a. If the process material is conductive, it is normal to
measure some resistance between sensing element
connections. The lowest permissible resistance values
are:
Center Wire to Ground
Center Wire to Shield
Cote Shield to Ground
b. If all measurements are open circuit the sensing element
has passed the test. If lower resistance was measured
continue with testing.
3. Clean sensing element and repeat resistance measurements
with the sensing element external to the vessel.
a. A clean sensing element should measure an open circuit
on all resistance tests.
b. If resistance values increase to an open circuit the
resistance was installation or coating related. The most
common causes are:
i. Cote Shield element does not extend sufficiently into
the vessel. Verify the CoteShield element extends at
least 2" into the vessel and past wall build-up.
ii. Extremely conductive coating on the sensing element.
This may require changing the sensing element or
electronics. Contact the factory for recommendations.
iii. Sensing element is touching vessel. A resistance
reading of less than 10 ohms to ground (sensing
element housing or tank) is usually due to a metal-to-
metal short circuit. Verify that the sensing element
is not touching any vessel structure.
24
that is set to the R x 1K ohm
1
1000 ohms.
600 ohms.
300 ohms.
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