Ludlum Measurements 2241-2, Manual

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Model 2241-2RK Technical Manual
Section 4
Ludlum Measurements, Inc. Page 4-4 July 2012
DISC 1 and DISC 2
(Discriminator 1 and 2): two independent multi-turn
potentiometers (approximately 20 revolutions) used to vary the detector
pulse-counting threshold from 2 to 100 millivolts for
DET
1 and
DET
2
respectively. A Ludlum Model 500 Pulser or equivalent should be used
in checking or adjusting the pulse discrimination parameter.
Note:
When making adjustments to the
HV
potentiometers, make
note of the following precautions: Use a Ludlum Model 500
Pulser or high-impedance voltmeter with a high-voltage probe
to measure the high voltage at the detector connector. If a
Ludlum Model 500 Pulser is not available, ensure that the
impedance of the voltmeter used is 1000 megohms or greater.
HV1, HV2
: multi-turn potentiometers (approximately 20 revolutions)
that varies the detector voltage from 200 to 2500 volts. The maximum
high-voltage output is adjusted by the
HV LIMIT
potentiometer located
on the internal main board.
OVL (Detector Overload)
: a multi-turn potentiometer (approximately
20 revolutions) that adjusts the detector current level that must be
exceeded to initiate an
OVERLOAD
alarm. This control adjusts the
current level discrimination point from 0.5 and 40 microamperes,
corresponding to the specific detector saturation point.
Main Board Controls
Note:
To access the internal circuit boards, unlatch the latches at
each end of the Model 2241-2. Carefully separate the top
chassis from the bottom cover (referred to as a can). The can
has the audio speaker (unimorph) with a two-conductor cable
attached to the main board. The audio plug may be
disconnected during the internal control adjustments.
HV LIMIT (R027)
: a multi-turn potentiometer (approximately 20
revolutions) sets the maximum HV limit with the front panel
HV
control
adjusted to the maximum clockwise position. It is adjustable from 1250
to 2500 Vdc.