14
3.2.4.2 Testing
The detecting unit should be tested according to 2.2.3.
3.2.4.3 Calculation of main relative error at gamma radiation DER measurement
3.2.4.3.1 Prepare the УПГД-3В standard equipment of gamma radiation for operation.
3.2.4.3.2 Fix the detecting unit in the УПГД-3В carriage holder, so that the mechanical center
of gamma quanta beam coincides with the center of detectors. The detector center is marked with
a «+» on the case of the detecting unit.
3.2.4.3.3 Prepare the PC-based data display system for operation according to 2.2.3.1 of
the OM. Connect the detecting unit to the adapter with the help of the ВІСТ.685621.002 service cable
and perform the operations according 2.2.3.3 of the OM.
3.2.4.3.4 In three minutes perform five measurements of gamma background DER indoors with
10 s interval.
3.2.4.3.5 Register the received readings in the protocol. Calculate the average value of gamma
radiation DER by the formula:
5
)
10
(
5
1
*
*
=
=
i
i
H
H
(3.1)
3.2.4.3.6 Place the УПГД-3В carriage with the detecting unit in a position, where gamma
radiation DER from
137
Сs source is equal to
)
10
(
0
*
H
= (0.8
0.1)
µSv/h.
3.2.4.3.7 In three minutes perform five measurements of DER with 10 s interval.
Register the received readings in the protocol.
3.2.4.3.8 Calculate the actual value of gamma radiation DER
*
H
(10) expressed in
microsieverts per hour by the formula:
)
10
(
)
10
(
)
10
(
*
*
*
Ф
H
H
H
−
=
(3.2)
where
)
10
(
*
H
- is an average value of the detecting unit readings form the source and
external gamma background, calculated by the formula (3.1), µSv/h;
)
10
(
*
H
Ф
- is an average value of the detecting unit readings at measurement of gamma
background indoors, µSv/h.
3.2.4.3.9 Calculate the main relative error limit of gamma radiation DER measurement,
expressed in percentage, following the procedure specified in ДСТУ ГОСТ 8.207:2008 standard.
3.2.4.3.10 Calculate the confidence limit of relative random error of measurement results
(
)
10
(
*
H
)
by the formula:
S
t
=
(3.3)
where
t
=
2.78 – is a Student coefficient at confidence probability of
P
=
0.95,
n
= 5;
S
- is a relative root-mean-square deviation of measurement results, calculated by the
formula:
(
)
)
1
(
)
10
(
)
10
(
)
10
(
1
1
2
*
*
*
−
−
=
=
n
n
H
H
H
S
n
i
i
(3.4)
