SAIC Exploranium – GR-135 System Manual page: 39
c) SAMPLE TIME – sets the SEARCH analysis sample time – selections are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
15, 20, 50, 100 secs - this parameter only applies to SEARCH mode data analysis. In the SEARCH
mode it is usually essential to operate at a 1sec rate or it is too easy to miss a source as the user
moves the instrument past the container/vehicle of interest.
d) NE IDENT THR – sets the alarm threshold level in the IDENTIFY mode – selections are OFF, 1, 2, 3,
4,
5, 6, 7, 8, 9, 10, 15, 20, 50, 100 counts. When the user enters the IDENTIFY mode, the normal
Neutron alarm system is disabled. Instead the system accumulates the sum of all Neutron counts
detected in the IDENTIFY sample period. Thus for the default IDENTIFY sample time of 30 seconds
– once IDENTIFY is started, an internal counter counts all Neutron pulses detected in the 30 second
sample time. At the end of this period the TOTAL COUNTS are then compared to the NE IDENT
THR which is also set in counts. If the TOTAL COUNTS exceed the threshold set then the word
NEUTRONS appears on the NUCLIDE ID display followed by a number either in counts or uSv/h
depending on the setting of the next parameter. If the TOTAL COUNTS is below this threshold then
only the normal Nuclide ID data is displayed.
e) NE UNIT – sets the Neutron UNITS used for display – selections are
cps or uSv/h. The IAEA has
decided that most users are best suited to see the Neutron data in estimated Dose Rate in uSv/h.
However some users prefer to see the raw Neutron counts. So this parameter permits the user to
select what they require.
10.4 DOSE
These selections set the DOSE parameters.
a) MEAS UNIT – sets the Dose measurement units – selections are
R, Sv, Gy
Gy (GRAYS) : the system is calibrated to the AIR KERMA RATE for Dose in GRAYS
R (Roentgen) : a conversion factor is used GRAYS -> R = x 114 (NUREC #ICRU-47)
Sv (Sievert) : Unit is directly calibrated in Ambient Dose Equivalent (H*10), (H*10 is the
International cal standard for Dose)
b) SAMPLE TIME – sets the Dose update sample time – selectable
1, 2..10, 20 ..60 seconds
This sets the actual update time in seconds of the DOSE measurement. If a 5 second sample time is
selected when the DOSE mode is started, the display shows “0” for 5 seconds and then displays the
current reading. This display will then stay constant for another 5 seconds and then the new value
will be seen.
c) AVERAGING – selects data averaging. Settings are
3P, 5P, 10P, OFF. This uses a selectable
running mean updated at the sample rate. So a sample rate of 1 second and a Averaging of 3P
means that the data is a 3 point average updated every second.
d) CORRECTION - Selections are: 80, 85, 90, 95,
100, 105, 110, 115, 120%
This feature permits users to change the Dose Calibration to suit local standards. The system should
correctly be set for 100%. However if a local calibration shows that the system is reading +10%
high, then adjusting this parameter to -10% will correct the data to achieve local calibration.
NOTE : Users should leave this setting at 100% if at all possible as careful calibration has shown
that this is the correct value and many calibration facilities may be inaccurate at the lower Dose
levels used in the GR-135
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