Ludlum Measurements 2241-3, Manual

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Model 2241-3 & 3i Technical Manual
Section 8
Ludlum Measurements, Inc. Page 8-12 January 2016
D
ETERMINING
CC
AND
DTC
This procedure contains the algorithm ( hi-lo method) for determining the CC
(Calibration Constant) and the DTC (Dead Time Correction). An example
of the Ludlum Model 44-9 GM detector calibration is used in conjunction
with the algorithm calculations to aid in solving the equations.
Note:
Ludlum Measurements, Inc. offers a PC-compatible software
program, which incorporates the read/write commands
necessary to communicate between a PC and the
Model 2241-3. The program also incorporates the algorithm to
calculate the detector CC and DTC. The software is offered in
a DOS version (part number 1370-025) or a WINDOWS
version (part number 1370-024). Read the Software License
Agreement at the close of this section prior to installing any
LMI software.
Hi-Lo Method
: The hi-lo method refers to the placement of the detector in a
radiation field using a two-point (CC and DT) calibration to make linear the
detector response, even in the non-linear operating regions of the detector.
The low-radiation field (CC) should be a field that yields from 2 to 5 %
count loss. The high radiation field (DT) should be a field that yields from
30 to 60 % count loss. The algorithm ignores background counts, and
therefore, the low field must be at least ten times the background count.
The following summary lists the calibration constraints.
Calibration and Dead Time Calibration Constraints
FIELD CONSTRAINT
BACKGROUND *10 times less than low field
LOW FIELD Yields from 2 to 5 % count loss
HIGH FIELD Yields from 30 to 60 % count loss
* This constraint only applies when using two sources (two fields) or a
radiation range calibrated without background consideration.