MODEL 2224-1
Technical Manual
Section 6
Ludlum Measurements, Inc.
Page 6-1
January 2012
Calibration and Maintenance
Calibration
Note:
Local procedures may supersede the following.
E
STABLISHING AN
O
PERATING
P
OINT
The detector operating parameters are established by adjusting the detector
operating voltage (
HV
), alpha threshold, and beta window to find an
optimum efficiency for the alpha/beta scintillator or proportional detector.
The threshold and window parameters can be adjusted to optimize
alpha/beta count discrimination, count efficiency, and minimize "cross talk"
between channels. Refer to the specific detector Operation Manual or
calibration certificate for the suggested threshold and window settings.
Once the thresholds and window settings are established, an operating
voltage versus count rate plot should be performed for both alpha and beta
count channels with alpha and beta particle emission sources.
The following procedure is an example of determining the operating voltage
for an alpha/beta scintillation or proportional detector:
1.
Connect a Ludlum Model 500 Pulser or equivalent to the
Model 2224-1.
2.
Switch the Model 2224-1 channel
selector to the β position.
Adjust the beta threshold (
BT
) for 3.5 mV and the window
(
BW
) for 30 mV. The pulser counts should be detected on
the Model 2224-1 ratemeter above 3.5
±
1 mV and should
shut off above 30 mV.
Section
6