Model 15
Technical Manual
Section 6
Ludlum Measurements, Inc.
Page 6-1
June 2020
Calibration and Maintenance
Calibration
Calibration controls are located on the front of the instrument under the
calibration cover. The controls may be adjusted with a 1/8-inch blade
screwdriver.
Note:
Measure high voltage with a Ludlum Model 500 Pulser or a
high-impedance voltmeter with a high-meg probe. If one of
these instruments is not available, use a voltmeter with a
minimum input resistance of 1000 megohms.
Calibration of Discriminator
Set the instrument range switch to X10. Remove the calibration cover
plate. Connect the Model 15 to the Model 500 Pulser. Set the pulser’s
pulse height to 10
±
0.5 mV for use without a GM detector. If a GM
detector is used, set the pulse height to 30
±
0.5 mV. Set the pulser’s
pulse rate to 400 × 10 counts per minute.
Adjust the
DIS
control until the meter reading increases from 0 to a
stable reading near 400 counts per minute. Check the adjustment by
lowering the Model 500 pulser’s pulse height to 9 mV for 10 mV setting
or 29 mV for 30 mV setting. Meter reading should drop to 0. Increase
the Model 500 pulse height to 12 mV for a 10 mV
DIS
setting or 32 mV
for a 30 mV
DIS
setting. Meter reading should increase to a stable value
near 400 counts per minute.
Calibration of Ratemeter
Set the Range switch to X1000. Set the pulser’s pulse rate to 400 × 1K
counts per minute. Set the pulser’s pulse height to 20 mV for a
DIS
setting of 10 mV or 60 mV for a
DIS
setting of 30 mV.
Section
6
