Ludlum Measurements 2241-2, Manual

Page: 54 / 93

Model 2241-2RK Technical Manual
Section 8
Ludlum Measurements, Inc. Page 8-13 July 2012
Preliminary CPS Setup
Refer to Section 8, Subsection “Function Switch Position Descriptions and
Variables,” for cps readout variables.
Select position
DET
1 on the toggle switch located on the front panel.
Starting with
FUNCTION
switch position 1, enter the following variables:
SWITCH POS. PARAMETER FUNCTION
1 0000s
-6
Dead Time
2 0100 -2 Calibration Constant
3 C/ Display Units
4 m Timebase
5 N/A Audio DivideBy
6 N/A Response Time
7 N/A Ratemeter Alm./Alert
8 0060 s ScalerAlm./Count Time
9 Not Used
A Not Used
B N/A LCD Backlight
C 000 C/s Set Minimum Display
D-F N/A RS-232 Parameters
Equation 2
DT x 19
1
=
CPS
LO
5%
The equations to the left (Equations 1-4) determine the hi and lo
radiation fields used to acquire counts for the CC and DTC algorithm.
These calculations require an unknown variable, DT (Dead Time).
Typical dead times for some of the standard LMI detectors are
referenced in the table at the end of this section. The lo count field
should be a field which yields between 2 and 5% count loss. The hi
count field ( CPS HI ) should be a field that yields between 30 and 60%
count loss.
Equation 1
DT x 49
1
=
CPS
LO
2%
Equation 3
DT x 2.3333
1
=
CPS
HI
30%
Equation 4
DT
1.5
=
CPS
HI
60%