AJAH.418266.007RE
6
Not e – Typical value of sensitivity coefficient is K = 2.0·10
-6
Sv·h
-1
·s and that of “dead time” is M = 23.0
s.
Sensitivity coefficient and “dead time” are written in the nonvolatile memory of the detector at
the time of adjustment. Reading and changing of these parameters, as well as other adjustment and
calibration operations are performed using the “TETRA_Checker” software.
1.4.4 The user can select one of the following algorithms of count rate measurements:
“Sliding” and “Following”.
1.4.4.1 The “Sliding” algorithm is used when the detector constitutes a part of a dosimetric
system.
The “Sliding” algorithm (moving average method) provides continuous measurement of the
count rate and calculation of average count rate in the “sliding window” with the width determined by
parameters “Interval quantity” and “Interval time” in seconds.
Average count rate is calculated by the formula
k
t
N
n
)
1
k
(
j
j
i
i
j
(1.3)
where
j
n
– is the average count rate in
th
j
“sliding window”, s
-1
;
i
N – is the number of pulses, registered during the
th
i
time interval;
t
– is the time of interval; t is equal to 5 seconds;
k
– is the interval quantity; t is selected by operator within the range 1 to 60.
The interval time can be changed by operator by means of “TETRA_Checker” software in the
range from 1 second to 65535 seconds.
Generation of the “Alarm” signal begins when the AEDR of neutron radiation exceeds
corresponding threshold set by operator. The “Sliding” algorithm allows smoothing of fluctuations of
the count rate and prevents false alarms, but at the same time the respond to dynamic changes of the
radiation intensity is delayed to some extent. The delay is determined by the algorithm parameters: the
interval time and the
i
nterval quantity.
By default the following parameters are set for the “Sliding” algorithm: interval quantity – 2;
interval time – 20 s. The algorithm provides regular updates of readings on the device’s display in
periods equal to interval time in seconds.
1.4.4.2 The “Following” algorithm is used when the detector constitutes a part of a dosimetric
system.
The “Following” algorithm provides cyclic measurement of the number of pulses and
calculation of the average count rate by the formula
i
N
n
j
1
i
i
i
(1.4)
where
i
n – is the average count rate, s
-1
;
i
N – is the number of pulses, registered during i-th second of the measurement cycle;
t
– is the measurement cycle duration, from 1 to 200 second.
Restart of the measurement cycle in case of fluctuations of the measured quantity exceeding
three standard deviations
of its current value is performed automatically.
Standard deviation
, where N is the count rate.
This ensures relatively fast response to changes of the radiation intensity and generation of the
“Alarm” signal at the moment when the AEDR of neutron radiation exceeds the threshold set by
operator.
