AMES MRS 110B-1 User manual

RADIOLOGICAL MONITOR
MRS 110B-1
AMES d.o.o. Automatic Measuring Systems for the Environment
Jamova 39, Ljubljana, Slovenia
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[email protected]i
http://www.ames.si

Radiological monitor MRS 110B-1 Manual
2 AMES d.o.o. Jamova 39, Ljubljana, Slovenia

Radiological monitor MRS 110B-1 Manual
AMES d.o.o. Jamova 39, Ljubljana, Slovenia 3
CONTENTS
1. DESCRIPTION OF MRS 110B-1............................... 5
1.1 TYPE OF DETECTED RADIATION................................... 6
1.2 DESCRIPTION OF THE MEASURING METHOD .......... 7
2. USE OF MRS 110B-1 ................................................... 8
2.1 TURNING THE INSTRUMENT ON.................................... 8
2.2 WORK WITH THE INSTRUMENT..................................... 8
2.3 SWITCHING BETWEEN MEASURING UNITS (cpm / µSv/h) 9
2.4 SETTING THE ALARM LEVEL .......................................... 9
2.5 SERIAL NUMBER................................................................. 9
2.6 TURNING THE INSTRUMENT OFF.................................. 9
3. MAINTENANCE ............................................................. 10
4. TECHNICAL DATA........................................................ 11
5. WARRANTY.................................................................... 12

Radiological monitor MRS 110B-1 Manual
4 AMES d.o.o. Jamova 39, Ljubljana, Slovenia

Radiological monitor MRS 110B-1 Manual
AMES d.o.o. Jamova 39, Ljubljana, Slovenia 5
1. DESCRIPTION OF MRS 110B-1
Radiological monitor MRS 110B-1 is digital pocket instrument, intended to
measure the exposed dose rate of roentgen, gamma and beta radiation.
Detector of MRS 110B-1 is thin-wall, cylindrical halogen Geiger Mueller tube
with the cross section of approximately 600 square millimetres. Since the
device measures roentgen, gamma and beta radiation only, the equivalent
dose rate is equal to the absorbed dose rate.
MRS 110B-1 measures the exposed dose rate in counts per minute (cpm) or in
micro Sieverts per hour (µSv/h). To switch between both units, press SET, than
use up or down arrows to select the desired unit and confirm the selection with
pressing SET again.

Radiological monitor MRS 110B-1 Manual
6 AMES d.o.o. Jamova 39, Ljubljana, Slovenia
It is to be mentioned that MRS 110B-1 gives the exact values of dose rate,
measured in µSv/h, only for the photon energy that was used as the calibration
source. For all other photon energies, the measuring error due to the energy
nonlinearity of the GM tube should be taken into the consideration.
Results of measurements are, together with the selected measuring unit,
shown on the liquid crystal display. Each detected pulse is heard as an
audible signal. Different sounding reports, that the dose rate has exceeded
the predetermined alarm level. Procedure, how to set the alarm level, is
described further in this Manual.
1.1 TYPE OF DETECTED RADIATION
If the side of MRS 110B-1, where the GM tube is mounted (marked with the
red dot), is close to the source, instrument detects all three sorts of radiation.
Otherwise, due to the poor penetration of beta rays, only roentgen and
gamma radiations are detected.

Radiological monitor MRS 110B-1 Manual
AMES d.o.o. Jamova 39, Ljubljana, Slovenia 7
1.2 DESCRIPTION OF THE MEASURING METHOD
Geiger Mueller tube detects photons that hit it and produces an electric pulse
for every detected photon. When we are measuring natural background, there
are normally 15 to 20 pulses per minute, which means in average one pulse
every 3 seconds. Time distribution of pulses is random. To achieve low
statistical uncertainty of the measured results, one should count pulses over
the longer time interval, since the relative statistical uncertainty is given with
the expression 1/√N (or, in percents, with 100/√N).
MRS 110B-1 uses the following measuring algorithm:
Instrument counts pulses in 2-second time intervals, storing data to the
internal memory. Each 2 seconds it computes the new sum of pulses by
adding the 2-seconds data from the memory, from the latest sample back
(running average), until one of the two conditions is fulfilled:
•To sum 150 or more pulses
•To sum the contents of 30 intervals, this means pulses for 1 minute
back.
When first or second condition is true, MRS 110B calculates new cpm value.
With the described algorithm, we achieve the following:
Under conditions, where there are only few cpm from the GM tube
(background measurements), summing time is limited to 1 minute. This also
defines the time response of the instrument. At 20 cpm, statistical uncertainty is
equal to 1/√20= 22.4%, with the response time of maximum 1 minute. When we
approach the radiation source, response time is, depending on the source activity,
significantly shorter (down to 2 seconds). In this case, count is limited by minimum
count of N=150 pulses, that gives the statistical uncertainty 1/√150= 8.2% or better.
Since MRS 110B-1 works with the running average that is updated every 2
seconds, measuring is smooth and without jumps in results, caused by the random
distribution of impulses.

Radiological monitor MRS 110B-1 Manual
8 AMES d.o.o. Jamova 39, Ljubljana, Slovenia
2. USE OF MRS 110B-1
2.1 TURNING THE INSTRUMENT ON
MRS 110B-1 is switched on by pressing the “ON” key. Immediately after this,
self-test is done: all segments of LCD are turned on and content of EEPROM
is checked. If an error is detected in EEPROM, message "Err0" is displayed
on the LCD and instrument runs with the default settings. Default values are
summarized in the section »SETTING THE PARAMETERS".
After instrument being turned on, measured value slowly rises to the “real”
value. Velocity of approaching the “real” value depends on the measured
activity, but in all cases MRS 110 B-1 after 1 minute shows result within the
declared statistical uncertainty.
2.2 WORK WITH THE INSTRUMENT
MRS 110 B-1 (after at least 1 minute from the switch-on) is carried by an
operator as a personal radiation meter. Acoustic signals indicate passing of
photons through the GM tube. When there is no elevated background,
approximately 20 short beeps are heard each minute, MRS 110 B-1 showing
aprox. 20 cpm. If we detect an increased frequency of beeps (or increased
value on LCD), this means that we are approaching the source of ionising
radiation.
In this case we turn the side of MRS 110 B-1, marked with the red dot (side
with the GM tube), towards the source. Beeping immediately follows the
radiation strength, LCD result, due to the numeric filtering, with slight delay.
In any case, at latest after 1 minute, result is accurate within the statistical
uncertainty.
If alarm level is exceeded, acoustic alarm is heard.
Measuring results are shown on LCD both in digital and in analogue form.
Range is automatically scaled to the range of the measured value. For the
analogue scale, factor in the upper right corner shows the power of 10, with
which readings on the semicircular scale should be multiplied.
At extremely high dose rates, GM tube becomes saturated. MRS 110 B-1
detects it and starts emitting continuous sound. Such audible signal warns us,
that radioactivity is over limits, measurable with MRS 110 B-1.

Radiological monitor MRS 110B-1 Manual
AMES d.o.o. Jamova 39, Ljubljana, Slovenia 9
2.3 SWITCHING BETWEEN MEASURING UNITS (cpm / µSv/h)
To switch between units, press SET, than use up or down arrows to select the
desired unit and confirm the selection with pressing SET again.
MRS 110B-1 gives the exact values of dose rate, measured in µSv/h, only for the
photon energy that was used as the calibration source. For all other photon
energies, the measuring error due to the energy nonlinearity of the GM tube must
be taken into the consideration.
2.4 SETTING THE ALARM LEVEL
To set the alarm level, press “SET” twice. After this, current alarm level is
displayed, which can be modified by pressing “up” or “down” arrows. Selection
of alarm value is confirmed by pressing “SET” again.
As the default alarm value, we recommend to set few times the background
value (e.g. 0,4 µSv/h).
If we do not confirm new value of alarm, MRS 110 B-1 after few seconds
automatically returns to the measuring mode.
2.5 SERIAL NUMBER
Serial number is displayed by pressing “up” arrow when in measuring mode.
2.6 TURNING THE INSTRUMENT OFF
MRS 110B-1 is switched off by pressing OFF key.

Radiological monitor MRS 110B-1 Manual
10 AMES d.o.o. Jamova 39, Ljubljana, Slovenia
3. MAINTENANCE
Battery of MRS 110 B-1 enables approximately 24 hours of continuous
operation. Instead of NiCd accumulator, normal 9 V battery can be used (in
this case, charging is not allowed!!!).
MRS 110 B-1 detects low battery voltage and warn us with displaying LOBAT
on the LCD. If instrument is running with the accumulator battery, charger
should be connected to the jack on the side of MRS. Battery charging should
be continuously for 14 hours.
In case of the normal battery replace it with the new one.