KATA DGM-1500 Turva User manual

Manual
DGM-1500 Turva
Personal Survey Meter
Made in Finland

THE DGM-1500 PERSONAL SURVEY METER
Safety is one of the most basic of human needs. In our modern day society of rapid
technological change there is also a growing need to develop the means of ensuring this
safety. The DGM-1500 is designed to improve the quality of radiation measurements both
in the workplace and the home environment. In the event of a crisis or nuclear accident it
becomes an invaluable tool.
The design of the DGM-1500 complies with official recommendations and requirements,
and reflects the expertise and experience gained by the manufacturer over a long period of
time in real life radiation measurement situations.
The DGM-1500 provides, in a single instrument, the means of performing an exceptionally
wide variety of radiation measurements accurately and reliably. It is a true radiation
multimeter with a wide field of application, encompassing the needs of state and civil
defense authorities at one end of the scale and those of the private citizen at the other.

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Table of contents
1 DGM-1500 TURVA PERSONAL SURVEY METER ...................... 2
2 OPTIONAL ACCESSORIES ............................................................ 2
3 PUSH BUTTON FUNCTIONS......................................................... 3
3.1 Automatic dose rate and dose measurement ............................... 3
3.2 Additional functions .................................................................. 4
3.2.1 Measurement mode selection ............................................. 4
3.2.2 Fast measurement............................................................... 4
3.2.3 Precision measurement....................................................... 4
3.2.4 Programming the alarm limits ............................................ 4
4 ALARM TONES............................................................................... 5
5 SPECIAL DISPLAY MESSAGES .................................................... 5
6 USING THE DGM-1500 TURVA .................................................... 6
6.1 General...................................................................................... 6
6.2 Environmental measurements .................................................... 6
6.3 Dose measurement..................................................................... 7
6.4 Continuous measurement of ambient radiation........................... 7
6.5 Gamma radiation measurement in foodstuffs ............................. 8
6.6 About radiation units ............................................................... 11
7 TESTS/APPROVALS ..................................................................... 12
8 TECHNICAL SPECIFICATIONS .................................................. 13
9 CALIBRATION.............................................................................. 14

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1 DGM-1500 TURVA PERSONAL SURVEY METER
2 OPTIONAL ACCESSORIES
Mains adapter 9V Reg. 3 mm DIN connector
Wall-mounting bracket and fixing screws
Carrying case
Display
Dose
Sound
Power on
Power off
Display backlight

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3 PUSH BUTTON FUNCTIONS
3.1 Automatic dose rate and dose measurement
Power on The meter is switched on by pressing the ON-button. Each time it is
switched on the meter performs a self diagnostic routine, after which it
automatically starts measuring both the radiation dose rate and the
cumulative dose. Reliable measurement is obtained at normal ambient
radiation levels (appr. 0.04–0.20 microSv/h) in about 3 minutes. At higher
levels of radiation (from appr. 100 microSv/h) reliable measurement is
obtained already in about 5 seconds. The measurement range for
automatic operation is 0.07...100 000 microSv/h.
When the measured level exceeds 9999 microSv/h the result is displayed
in integer units of a thousand, rounded to the nearest thousand, followed
by the exponential symbol ‘E3’ (= x 10 to the power 3). For example, a
measured level of 55 425 microSv/h would be displayed as 55E3. The
measurement result is always in microSv/h.
Dose The dose register always contains the cumulative radiation dose whenever
the meter is in operation. This register can be cleared by the user at any
time if required. The measurement range of the dose register is
0.001...1000 milliSieverts. The cumulative radiation dose can be displayed
by pressing the DOSE-pushbutton and holding it down. The dose register
reading is always in milliSieverts (milliSv), where 1000 µS = 1 mSv.
Clearing the dose
register First switch the meter off. The dose register can now be cleared by holding
the O-pushbutton down while switching the meter on again. “d : 0” -
message is visible on the display on the startup if the dose register was
successfully cleared.
Alarm tone The alarm tone, which gives an indication of the radiation level, can be
enabled or disabled by means of this pushbutton.
Backlight The display backlight can be switched on for 5 seconds by momentarily
pressing this pushbutton.
Power off When the meter is switched off all settings and the contents of the dose
register are stored in non-volatile memory. This information is retained in
the non-volatile memory for several years, even if the battery is removed
from the meter.

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3.2 Additional functions
3.2.1 Measurement mode selection
In addition to the automatic mode there are two other user-selectable measurement
modes available. The O-pushbutton is used to step through the modes (fast
measurement - precision measurement - automatic measurement). Hold the O-
pushbutton down for at least three seconds to switch from the current mode to the next
mode in the cycle. The AUTO-message appears when the meter is in the automatic
measurement mode. The meter always returns to the automatic mode if it is switched
off momentarily and then on again, regardless of the previous mode.
3.2.2 Fast measurement
When this mode is selected the FAST-message appears in the display. The fast
measurement period is fixed at 1.25 secs, allowing fast pinpointing of radiation
sources. This mode is not suitable for measuring low level (ambient) radiation.
3.2.3 Precision measurement
When this mode is selected the letter ‘h’ appears in the display, indicating that the
measurement period is one hour (three hours). The radiation dose rate is displayed in
microSv/h. The expiration of each one hour period is indicated by a change in case of
the letter ‘h’ (h/H). This is the most precise measurement mode, and is particularly
suitable for measuring low levels of radiation. The range of measurement is 0.01...9.99
microSv/h. If the dose rate momentarily exceeds this range the meter will immediately
switch to the automatic mode. Precision measurement is operational at low dose rates
only. This is necessary to meet the requirement for fast response when the dose rate
increases.
3.2.4 Programming the alarm limits
Meter alarm levels for the dose rate and cumulative dose are user-programmable. If
the dose rate or cumulative dose of the measured radiation reaches the alarm level
programmed for it the meter will emit an alarm tone. When the dose rate alarm level is
exceeded the meter emits a periodic double beep. When the cumulative dose alarm
level is exceeded the meter emits a periodic single beep. The period of the double
beep alarm tone is slightly shorter than that of the single beep tone.
The programming mode is entered by pressing the TONE- and LIGHT-buttons
simultaneously. The O-button is then pressed to select the alarm level to be
programmed: a ‘0’ in the display means dose rate alarm level, and a ‘1’ means
cumulative dose alarm level. The programmed alarm level can then be incremented by
pressing the DOSE-button or decremented by pressing the TONE-button. The rate at
which the programmed level changes when one of these buttons is pressed is slow at
first, but increases if the button is held down continuously. When both alarm levels
have been set the O- and LIGHT-buttons are pressed simultaneously to exit the
programming state.

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4 ALARM TONES
The meter provides six different alarm tones. Only one of these can be emitted at a
time. These alarm tones and their meanings are described below in order of
importance:
Meaning of tone Timing Duration
1. Battery voltage too low. - - - - - - - - - - - - - - - - 5 seconds
2. Radiation level exceeds measurement range. –– –– –– –– … continuous
3. Dose rate alarm level. - - - - - - … continuous
4. Cumulative dose alarm level. –– –– ... continuous
5. Button pressed. - single beep
6. Radiation pulse detected. - single beep
The symbols used in the timing chart above have the following meanings:
- = tone
= pause
... = sequence repeats
5 SPECIAL DISPLAY MESSAGES
: Low battery voltage warning. Appears in the display when the battery voltage
drops below a certain level. This indicates that the meter will operate for only fifty
more hours at the most, and that the battery should be replaced with a new one as
soon as possible. If the battery voltage continues to drop the meter will emit an
alarm tone for 5 seconds then switch itself off. This is done to ensure that data is
retained in memory, and in the case of NiCd batteries, to prevent complete
discharge of the battery.
OFL Out-of-range warning. This message will appear in the display when the dose rate
exceeds the meter’s measurement range. An alarm tone is also emitted.
xxE3 When the dose rate exceeds 9999 µSv/h it will be displayed in exponential mode in
integer units of one thousand. For example, a dose rate of 55000 µSv/h will be
displayed in the form 55E3.
Auto See section on measurement mode selection.
Fast See section on fast measurement.
h/H See section on precision measurement.
The meter executes a self-diagnostic routine to detect possible fault situations. If a fault is
detected the meter displays an error message consisting of the letters ‘Er’ followed by a
number. All error messages except Er1, which remains in effect until the fault has been
corrected, can be cancelled by pressing any function button.
The error messages are described below:

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Er 1 Indicates that the meter cannot function and must be sent for repair
immediately.
Er 10 Indicates loss of calibration coefficients. When this occur the internal average
default values will be used. This fault does not render the meter unusable, but
it may affect accuracy of the measurement. This message will always appear
in the display when the meter is switched on until the fault is repaired. The
meter should be sent for repair as soon as possible.
Er 11 Indicates losing of dose register contents. The user is advised to check the
value in the dose register and clear the register if required. The meter need
not be returned for maintenance provided the fault does not recurr.
Er 12 Indicates that the user-programmed alarm levels have changed and must be
reprogrammed. The meter need not be returned for maintenance provided the
fault does not recurr.
6 USING THE DGM-1500 TURVA
6.1 General
The DGM-1500 is a versatile survey meter intended for measuring gamma- and X-
radiation levels. Because of its wide range it can be used to perform many
different types of radiation measurement.
The DGM-1500 functions on two levels. On the basic level it is an easy-to-use
radiation meter which automatically measures both dose rate and cumulative
dose. All the user need do is switch the meter on. In addition to this, fast
measurement (FAST) and precision measurement (h) functions, which enable the
meter to perform special
measurements, are also available. There are separate user-programmable alarm
levels for dose rate and cumulative dose. If these levels are exceeded an audible
alarm is given.
Typical areas of application include measurements made by government
authorities (monitoring, data acquisition, inspections), civil defence, private sector
use (industry, business, institutions, offices), safety in the workplace (industry, X-
ray laboratories), gamma measurement of foodstuffs, and use as a personal
radiation meter.
6.2 Environmental measurements
The DGM-1500 is ideal for mapping the radiation level in a given area. Small in
size and battery operated it is easy to carry about. The fast measurement (FAST)
function is used to pinpoint radiation sources. The closer the meter is brought to
the radiation source the higher the reading obtained. Ambient radiation
measurements must be carried out over a longer period of time. Radioactive
fallout gives rise to radiation spots in the home environment. Attention should be

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paid to air conditioning filters, extractor fan filters, the base of roof gutter drainage
pipes, car fenders and air filters etc. and other places where dust or rain water
could collect.
6.3 Dose measurement
The DGM-1500 measures instantaneous dose rate and cumulative dose
simultaneously. Whenever the meter is in operation the dose register contains the
current cumulative dose. The cumulative dose can be displayed by pressing the
DOSE button.
For example, in a location where the dose rate is 8 microSv/h, the cumulative
dose over a period of 24 hours will be 0.192 milliSv. The contents of the dose
register are saved in non-volatile memory when the meter is switched off, so the
cumulative dose for the total time of operation of the meter is always available.
The contents of the dose register can be cleared by the user whenever required
(see ‘Clearing the dose register’ under paragraph 3.1).
6.4 Continuous measurement of ambient radiation
The DGM-1500 has a connector for a mains
adapter, allowing it to be used for round-the-clock
radiation monitoring. A wall mounting bracket for
the meter is available as an optional extra, so the
meter can be installed where it is always easily
visible. The alarm level is userprogrammable. If the
level of the measured radiation exceeds the alarm
level a warning tone is emitted (see the section on
programming the alarm level).
The level of ambient radiation at a given location is
fairly stable, but the differences in levels at different
locations are considerable. In Finland the level of
ambient radiation varies in the range 0.04 ... 0.20
microSv/h. The lowest level (0.04 microSv/h) is
encountered on a lake or at sea, where radiation
emitted by the earth is absorbed by the water mass, and cosmic radiation remains
as the primary source. Cosmic radiation accounts for about 0.035 microSv/h of the
ambient radiation level measured at the earth’s surface.
Official measurements of ambient radiation are made in Finland at a height of 1 m
above the earth’s surface in a relatively open space.

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6.5 Gamma radiation measurement in foodstuffs
The DGM-1500’s precision measurement function enables the measurement of
extremely low dose rates, and therefore extends the area of application of the
meter considerably.
When a nuclear disaster occurs radioactive substances may be carried in the
atmosphere for thousands of kilometres. Radioactive dust is deposited on the
earth’s surface by rain and other precipitation to form an uneven radiation field.
Radionuclides become part of the natural food cycle and eventually reach the
dinner table via plants and animals. A large number of radioactive substances are
released in a nuclear accident, a high proportion of these are gamma radiators. By
screening foodstuffs before they are used excessive gamma radiation can be
detected and the food cleansed. For example, Cesium-137 can be removed by
soaking the food in purified water. Cesium is soluble in water so slivers of meat,
for example, can be cleansed in this way. By monitoring the radiation level the
effectiveness of the decontaminating process can be assessed and, if necessary,
the cleansing process repeated with fresh purified water.
It should be noted that the authorities may impose limitations on the consumption
of foodstuffs in situations in which there is no necessity for shelter against external
radiation.
The rate at which radioactivity decreases is determined only by the half-life of the
radionuclide in question. The half-life of Cs-137 is 30 years, which means it takes
30 years for the level of radioactivity of Cs-137 to decrease by one half. Because
Cs-137 is soluble in water its so-called biological half-life is often quite short. This
means that most of the Cesium in animals will be removed within a few weeks if
they are fed uncontaminated food. The same applies to human beings.
To perform the measurement you will need
- a DGM-1500 radiation meter
- a 2-litre minigrip plastic bag
- a table
- a non-slip support for the meter
- some packing tape
Preparation
Position the table against a wall (not stone or brick). Place the meter on the
table, with a suitable non-slip support (e.g. foam rubber, rubber, styrox etc.)
underneath it, and lean it upright against the wall.