Model 15
Technical Manual
Section 4
Ludlum Measurements, Inc.
Page 4-2
June 2020
B-G/N
: This switch allows for selection of the desired detector and is
associated with the
HV
outputs. In the
B
-
G
position, the
HV
is adjusted
for approximately 900 volts for use with GM detectors. In the
N
position, the
HV
is adjusted for approximately 1275-1350 volts when
utilizing the Model 42-14H Neutron detector.
HV Pushbutton Switch
: When depressed, displays the detector high
voltage on the meter face, corresponding to the selected detector (
B
-
G
/
N
). The output resistance of the high-voltage supply is 1.5 megohms
with a typical scintillation voltage divider of 100 megohms. The actual
detector voltage will be 98.5% of the indicated voltage.
The following controls are located under the front-panel
calibration cover:
Discriminator Adjustment (DIS)
: allows the input pulse threshold to be
adjusted from 2 to 60 mV.
HVB Adjustment
: provides a means of varying the alpha-beta-gamma
high voltage from 200 to 2500 V; factory set at 900 V
Range Calibration Adjustments
: These adjustment controls allow
individual calibration for each range multiplier.
