Testing The Sensing Element - Ametek Drexelbrook Z-tron Level Control 502-302X Series Installation And Operating Instructions Manual

502-302 Series Z-tron
X
5.1 Testing the
Electronic
Unit (cont.)
5.2 Testing the
Sensing Element
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TM Level Control
a. Disconnect ALL wires from the sensing element
connection screws on the electronic chassis. See Figure
5-1.
b. Turn the operating point adjustment fully counter-
clockwise using an insulated tool.
c. Begin turning the operating point adjustment clock-
wise until the relay just changes states.
d. Rotate the tune point adjustment slowly back and forth
about this point. Observe the travel required between
relay energized and relay de-energized. The pointer
should travel less than 1/4 turn to operate the relay. If
so, the unit is working properly.
e. If you are unable to find a tune point over the full
travel of the setpoint adjustment, the unit has failed.
Contact your local Drexelbrook representative or the
Factory Technical Service department at 1-800-527-
6297.
The following procedure is used to test the sensing element:
a. If the electronic unit is integrally-mounted, remove all
wires leading from the sensing element to the electronic
unit.
If the sensing element is remotely-mounted, disconnect all
three coax leads at the sensing element screws of the
electronic unit.
b. On remote-mount systems, remove spark protector if
present.
c. Use an analog ohmmeter* that is set to the R x 1K ohm
scale. Measure the resistance between all three sensing
element terminals. See Figure 5-2.
Center wire to ground __________
Center wire to shield
Shield to ground
*Use an analog ohmeter because the ohms/volt rating is
lower and it therefore provides more current to measure
the resistance. A digital meter does not measure resistance
in the same way.
21
Troubleshooting
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