Model 15
Technical Manual
Section 6
Ludlum Measurements, Inc.
Page 6-2
June 2020
Now adjust the X1000 calibration potentiometer until the Model 15
reads 400 × 1000 counts/minute. Reduce the pulser’s pulse rate to 100
× 1K counts per minute. Confirm that meter reading is 100
±
10.
Set the pulser’s pulse rate to 400 × 100 counts per minute. Set the
Model 15 range switch to X100. Adjust the X100 calibration
potentiometer until the Model 15 reads 400 ×100 counts per minute.
Reduce the counts on Pulser to 100 × 100 counts per minute and
confirm that the Model 15 reads 100
±
10. Repeat the procedure for the
X10 and X1 ranges.
Calibration of High Voltage Readout
Open the instrument and locate the
HV
calibration control on the main
circuit board. Connect the Model 15 to the Model 500 Pulser. Set the B-
G/N switch to N. Press the
HV
Test switch and record the
HV
reading
on both the Model 500 and the Model 15.
Adjust the
HVN
potentiometer for 1500 V on pulser readout. Press the
HV
button and adjust the internal Model 15
HV
control until the meter
reads 1500 V. Reduce the
HVN
control for 1000 V on pulser
HV
readout.
HV
test should indicate 1000
±
10%. Increase the
HVN
control to 2000 V
on Pulser
HV
readout.
HV
test should indicate 2000
±
10% V.
Calibration of High Voltage
(For Beta Gamma Set
B
-
G
/
N
to
B
-
G
.) Press the
HV
test switch and adjust
the
HVB
calibration potentiometer for a reading of 900 V.
Calibration of High Voltage For Neutrons
Switch the
B
-
G
/
N
switch to
N
. Connect the neutron probe. Press the
HV
test switch. Record readings in a known neutron field as the high voltage
is varied from approximately 1200-1500 V in 50 V steps.
Expose Neutron detector to a 1 R/hr gamma field. Reduce the high-
voltage setting until count rate is less than 10 counts per minute.
