Alcad AT30 SERIES, Operating And Service Instructions

Page: 38 / 100

OPERATING THE AT30
34
Adjusting Ground Detection Sensitivity
You can adjust the sensitivity of
the ground detection alarm circuit.
You must have a test resistor
whose value is the sensitivity you
want. You can adjust the
sensitivity from 5 to 50 k
Ω
.
The potentiometer for adjusting
ground detection circuit
sensitivity is located on the main
control circuit board. It is the
lower of the two potentiometers
labeled
RA3 SENS , as shown in
the figure at the right.
NOTE: Do not try to adjust the upper potentiometer labeled RA2
BALANCE . This adjustment is made at the factory for proper
circuit operation.
CAUTION: Before connecting or disconnecting a test resistor,
de-energize and lock out all ac and dc voltage sources to the
AT30. Check with a voltmeter before proceeding. Restart the
AT30 only when necessary to make the sensitivity adjustment. If
your battery is grounded, do not attempt this procedure.
Remove the safety cover. Connect the test resistor between
TB1(+)
and
the ground terminal. Refer to the standard internal component layout
drawings starting on Page 72 in Appendix C For I/O panel layout and all
terminal wire specifications.
Adjust
RA3
counterclockwise until the
front panel indicator goes out, and adjust
slowly clockwise until the
POS GND
indicator just lights.
Make this adjustment slowly, for the
indicator is updated once every four
seconds. De-energize and lock out power
to the AT30. Remove the test resistor
and verify that the indicator goes out.
Connect the test resistor between
TB1(-)
and chassis ground Verify that the NEG
GND
indicator lights. If not, adjust
RA3
clockwise until it does. Remove the test
resistor.