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Model 78 and 78-1 Technical Manual
Section 8
Ludlum Measurements, Inc. Page 8-4 March 2021
Loading Default Parameters
To load the default parameters for all detector setups, hold down the
UP
pushbutton on
the switch board until
DEF
is displayed on the LCD. The following table shows the
default values.
Model 78 (-1) mR/hr (µSv) R/Hr (mSv)
Setup 01 Setup 02
Dead Time 75
µs
ec 40
µ
sec
Cal Const 645e+5 100e+4
Series Const 0 300
Rate Alarm 500 mR/hr 500 R/hr
Scaler Alarm 85000 85000
Count Time 12 sec 12 sec
Time Base sec sec
Units R/hr R/hr
Audio Divide By 1 1
Response 0 0
Check Source 0 0
Percent CS 0 0
Rate Alert 450 mR/hr 450 R/hr
Min Display 00.0 µ R/hr 00.0 µ R/hr
Baud Rate 9600
LCD Time Off 5 sec
Detector 0
Calibration
The Model 78 calibration routine consists of entering detector parameters into memory
by way of the switch board and adjusting the
CAL
controls (
HV
1,
HV
2,
DISC
and
OVL
) for
the specific detector operating requirements.
The first subsection of calibration will give a general overview of detector setup,
including the determination of various detector operating voltages (
HV
1 and
HV
2) and
the adjustment of counter input sensitivity (
DISC
).
The following subsection deals with exposure rate calibration. The detector Calibration
Constant (CC), Dead Time Correction (DTC), and Series Constant (SC) are the three
primary parameters used in the exposure rate calibrations (R/hr and Sv/h). These three
constants are varied to achieve linearity at the detector non-linear operating regions.
The last subsection of calibration deals with Detector Overload (
OVL
).