Model 12-4 Technical Manual Section 7
Ludlum Measurements, Inc. Page 7-2 May 2016
SYMPTOM
No power (or meter
does not reach BAT
TEST
or BAT OK
mark) (continued)
Nonlinear Readings
Meter goes full-scale
or “pegs out”
POSSIBLE SOLUTION
3. Check battery contacts. Clean them
with rough sandpaper or use an
engraver to clean the tips.
4. Check for loose or broken wires,
especially between the main board
and the high-voltage board.
1. Check the high voltage (HV) by
pressing the HV TEST button. If a
multimeter is used to check the
HV,
ensure that one with high impedance
is used, as a standard multimeter
could be damaged in this process.
2. Check for noise in the detector cable
by disconnecting the detector,
placing the instrument on the lowest
range setting, and wiggling the cable
while observing the meter face for
significant changes in readings.
3. Check for “sticky” meter movement.
Does the reading change when you
tap the meter? Does the meter needle
“stick” at any spot?
4. Check the “meter zero.” Turn the
power
OFF. The meter should come
to rest on “0.”
1. Replace the detector cable to
determine whether or not the cable
has failed, causing excessive noise.
2. Check the HV and, if possible, the
input threshold for proper setting.
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