Ludlum Measurements 3000 - Page 34

Model 3000 Survey meter User’s Manual Section 4
Ludlum Measurements, Inc. Page 4-9 April 2021
Detector
Dead Time
Calibration Constant
Model 44-2
10 µsec ±5 µsec
100e+08
Model 44-6
100 µsec ±35 µsec
709e+05
Model 44-7
262 µsec ±35 µsec
139e+06
Model 44-9
85 µsec ±35 µsec
200e+06
Model 44-38
100 µsec ±35 µsec
709e+05
Dead Time Correction 2 Mantissa (Default 0) - Tap ON/OFF to select the
value to adjust, and MODE to adjust the value. Available values are:
Ones Place (0-9)
Tens Place (0-9)
Hundreds Place (0-9)
Dead Time Correction 2 Exponent (Default 0) - Tap ON/OFF to select
the value to adjust, and MODE to adjust the value. Available values are:
Value between (-6 to -12)
Efficiency (Default 15.0%) - Tap ON/OFF to select the value to adjust, and
MODE to adjust the value. Available values are:
Ones Place (0-9)
Tens Place (0-9)
Hundreds Place (0-9)
Number of Decimal Places (0 or 1)
Normally the efficiency is used on a per detector basis or 4pi basis, i.e. the
efficiency of the detector is calculated by dividing the count rate received from a
source by the total disintegration rate of the source. When either dpm or Bq
units are chosen, the use of the 4pi efficiency allows the display of the source
size or activity on the Model 3000 display.
But if the user desires to have the Model 3000 show results in terms of
dpm/100 cm
2
, the user could manipulate the efficiency to produce this result by
multiplying the efficiency times the ratio of the detector area to 100 cm
2
. For
example, using a detector with an area of 15 cm
2
, if we start with 10% efficiency
to measure in dpm, then the parameter could be changed to 1.5% to measure in
dpm/100 cm
2
.