Polimaster PM1401MA User Manual

13
In the Search mode the instrument displays the current value of
gamma radiation count rate in s
-1
(counts per second) and automatically
compares the average count rate with the threshold value (the value based
on the background radiation measured during calibration and the n
coefficient set by the user). The lower line indicates the average statistical error of the
measured value in %.
In this mode, the instrument is capable of searching for and locating radioactive
sources. When a radioactive source is detected (the point at which the calculated alarm
threshold is exceeded), the instrument will produce a visual and audio and/or vibrating alarm.
As the PM1401MA moves closer to the radiation source, the frequency of audio or vibrating
signals increase and thus enable the user to determine the direction toward the source
location.
When the alarms signals reach their maximum frequency it is recommended to run the
background calibration procedure (see section Getting a new background). During this process
it is important to keep the instrument in the same place if possible. Once the background
calibration is completed, the user may then continue to search for the radiation source. If
necessary, this procedure may be repeated as many times as necessary until the gamma
radiation source is located.
Radioactive source localization also may be performed by monitoring of the numerical
value of gamma count rate on the display. The closer the instrument is to the radiation
source, the larger the count rate value. In this scenario it is not necessary to run background
calibration while approaching the source.
If the value of the dose rate exceeds the instrument’s upper measuring limit for
radiation, the overload message on the LCD screen will display “-OL-”
Alarms in the Search Mode
Alarm levels in the Search Mode are derived from the ambient background. When the
instrument runs through background calibration, it acquires a background reading and
calculates the alarm levels automatically based on the value of n coefficient set by the user.
The value of n coefficient may be set in the range of 1.0 to 9.9 through every 0.1. The
smaller is the value of n coefficient, the more sensitive is the instrument to changes in
background radiation, however this also increases the rate of “false alarms”. The larger is the
value of n coefficient, the less sensitive unit becomes to minor changes in radiation
background and responds only to large radiation field variations (intensive radiation sources
nearby) and probability of false alarms decreases.
Getting a new background
The user may run background calibration to adjust the alarm threshold for the new
background during the normal operation of the instrument. It is recommended to run the
background calibration any time the radiation background significantly changes, e.g. upon
entry or exit from the building, changing locations, etc.
If the instrument’s background radiation level is not updated, the alarm may be set off
more frequently in the Search Mode even without the presence of any radioactive sources. Or
conversely, the instrument’s ability to alarm to the presence of a radiation source becomes
worse. Under these circumstances it is necessary to run the background calibration so that
the instrument recalculates the alarm thresholds based on the new environment.
To update the background radiation levels and recalculate the thresholds, press and
hold down on the Mode button until the message “CAL” appears on the display. The unit
is now acquiring new background. In total, this process requires 60 seconds. When the LCD
screen display returns to the normal numeric display, the unit has modified its background
radiation levels to the new environment and is ready for normal operation.

Polimaster PM1401MA Specifications

General

Detectors Gamma	CsI(Tl) scintillator
Sensitivity, gamma radiation Cs-137 Am-241	100 s-1/(µSv/h) / (1 s-1/(µR/h)) 100 s-1/(µSv/h) / (1 s-1/(µR/h))
Energy range Gamma	0.06 – 3.0 MeV
Indication range Gamma	0.01 µSv/h – 99.99 µSv/h / (1 µR/h – 9999 µR/h)
Response time	0.25 s
Measurement range Gamma (± 30 % at 137Cs)	0.1 µSv/h – 70 µSv/h / (10 µR/h – 7000 µR/h)
Alarm types	visual, audible and external vibrator
Drop test	1, 5 m (5 ft.) onto concrete surface
Power requirements	one AA size battery
Battery lifetime	Up to 1000 hours
Communication	IR interface
Memory	990 data points
Environmental Temperature range LCD indication Humidity	-30 to +50 °C (-22 to +122 °F ) -15 to +50 °C (+5 to +122, 5 °F ) up to 95 % at +35 °C (+95 °F )
Ingress Protection Rating	IP65

Weight and Dimensions

Dimensions	110х57х32 mm (41/3 х 21/4 х 11/4 in)
Weight, including battery	320 g. (11.29 oz)