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Personal Radiation Detector
Operation Manual
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© 2015 IMI-International Medcom, Inc.
All rights reserved.
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Contents
1 Introduction ..........................................................................1
How the Rad 100 Detects Radiation .......................................1
Precautions ............................................................................2
2 Features ................................................................................3
The Display ............................................................................4
The Switches .........................................................................5
The Detector .........................................................................6
The Input/Output Ports ..........................................................6
3 Operation ..............................................................................7
Units of Measurement ...........................................................7
Starting the Rad 100 ..............................................................7
Operating in the Dose and Count Rate Modes .......................7
Operating in Total/Timer Mode ..............................................8
Operating Ranges and Response Times ................................10
The Utility Menu ..................................................................12
Interfacing to an External Device ..........................................13
4 Common Procedures ...........................................................14
Establishing the Background Count .....................................14
Environmental Area Monitoring ...........................................15
Checking an Object .............................................................15
5 Maintenance .......................................................................16
Calibration ..........................................................................16
Troubleshooting and Service ................................................19
6 Basics of Radiation and Its Measurement .............................21
Ionizing Radiation ................................................................21
Measuring Radiation ............................................................23
Radiation Measurement Units ..............................................24
Higher Than Normal Readings .............................................24
Appendix: Technical Specifications ...........................................26
Limited Warranty .....................................................................28
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1 Introduction
The Rad 100 is a health and safety instrument that measures alpha,
beta, gamma, and X-ray radiation. Its applications include:
• Monitoring possible radiation exposure while working with
radionuclides
• Ensuring compliance with regulatory standards
• Checking for leakage from X-ray machines and other sources
• Screening for environmental contamination or environmental sources
of radioactivity
• Connecting to a computer or data logger to record and tabulate your
data
How the Rad 100 Detects Radiation
The Rad 100 uses a Geiger-Mueller tube to detect radiation.
The Geiger tube generates a pulse of electrical current each time
radiation passes through the tube and causes ionization. Each pulse
is electronically detected and registers as a count. The Rad 100
displays the counts in the mode you choose: microsieverts per
hour (µSv/hr), counts (CPM), or total counts. If conventional
units (mR/hr) is preferred you can easily convert units displayed
in the Utility Menu.
The count or dose rate displayed by the Rad 100 updates every 3
seconds and fluctuates due to the random nature of radioactivity. Use
the Total mode feature on the instrument to get a highly accurate,
unfluctuating reading by taking a measuremement for a longer timed
period. For more information, see “Operating in Total/Timer Mode”
in Chapter 3.
Rad 100
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Precautions
To keep the Rad 100 in good condition, handle it with care and
observe the following precautions:
•
Do not contaminate the Rad 100 by touching it to radioactive
surfaces or materials.
• Do not leave the Rad 100 in temperatures over 122° F (50° C) or
in direct sunlight for extended periods of time.
• Do not get the Rad 100 wet. Water can damage the circuitry
and the coating of the mica surface of the Geiger tube.
• Do not put the Rad 100 in a microwave oven. It cannot measure
microwaves, and you may damage it or the oven.
• If you expect to not use the Rad 100 for longer than a few months,
remove the battery to avoid damage from battery corrosion.
•
Change the battery when the battery indicator appears on
the display.
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Rad 100
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2 Features
The Rad 100 measures alpha, beta, gamma, and X-radiation.
This chapter briefly describes the Rad 100's functions. For more
information on how to use the Rad 100, see Chapter 3, “Operation.”
The instrument counts ionizing events and displays the results on
the
liquid crystal display (LCD) (4). You control which unit of
measurement
When the Rad 100 is operating, the red count light (1) flashes
each time a count (an ionizing event) is detected.
1 Count
Light
is shown by using the Mode switch.
4 LCD
5 Mode
Switch
6 On/O/
Audio
Switch
2 Cal/Probe
Input Port
3 Output Port
7 +, –, and
Set Buttons
Rad 100
End Panel
8 Alpha
Window
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The Display
1 Count
Light
2 Calibration
Input Port
3 Output Port
4 LCD
5 Mode
Switch
6 On/Off/
Audio
Switch
End Panel
7 +, –, and
Set Buttons
8 Alpha
Window
Several indicators on the LCD show information about the mode setting,
the current function, and the battery condition.
E
D
Total Mode
C
Timer
B
Low Battery
Indicator
A
Numeric
Display
X1000
Mode
F
Average
• e numeric display (A) shows the current radiation level in the unit
specied by the mode switch setting.
• A small battery (B) appears to the le of the numeric display to indicate
low battery voltage.
•
An hourglass (C) appears during a timed count.
• TOTAL (D) appears when the Rad 100 is in Total/Timer mode.
•
X1000 (E) appears when the radiation level is high. Multiply
reading by 1,000 when this symbol is pre
•
AVG (F) appears when the Rad 100 is showing the average reading
for a timed count.
• CAL (G) appears while you are calibrating the Rad 100.
• SET (H) appears when you are setting the Timer, the calibration
factor, or working in the Utility Menu (the numeric display shows the
setting being adjusted instead of the current radiation level).
The current unit of measurement (I)—CPM, CPS, mR/hr, or µSv/hr—is
•
displayed to the right of the numeric display.
•
MENU (J) appears when you are in the Utility Menu.
RANGE:Full (K) appears when the radiation level goes beyond the
•
range that can be displayed.
G
Calibration
Mode
sent.
H
Timer or
Calibration
Set Mode
I
Units of
Measurement
J
Menu
K Range Full
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The Switches
The Rad 100 has two switches on the front and three buttons on the
end panel. Each switch has three settings, which are described below.
Mode Switch (5)
Dose Rate. e numeric display shows the current radiation level
in the selected unit of measurement. In SI units it shows the current
radiation level in microsieverts per hour, from .000 to 1100. In conventional units, it shows milliroentgens per hour from .000 to 110.
Count Rate. The display shows the current radiation level in
counts
per minute from 0 to 350,000
multiply the numeric reading by 1,000
Total/Timer. e display shows the accumulated total of counts
starting when the switch is turned to this position, from 0 to
9,999,000. When X1000 is shown, multiply the numeric reading
by 1,000 to get the complete reading.
On/Off/Audio Switch (6)
Audio. The Rad 100 is on, and it makes a clicking sound for
each radiation event detected.
On. The Rad 100 is operating, but audio is off.
Off. The Rad 100 is not operating.
+, –, and SET Buttons (7)
These buttons are used for setting the timer. They are also used
for calibration and for using the Utility Menu. For more
information, see “Taking a Timed Count,” “The Utility Menu” in
Chapter 3 and “Calibration” in Chapter 5.
. When X1000 is shown,
to get the complete reading.
Rad 100
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The Detector
The Rad 100 uses a Geiger tube to detect radiation. Alpha radiation
does not penetrate most solid materials, so this Geiger tube has a thin
disk of mica, which alpha radiation can penetrate, on its end. The
screened opening at the top of the Rad 100 is called the alpha window
(8). It allows alpha and low-energy beta and gamma radiation to
penetrate the mica end of the tube.
CAUTION: The mica end surface of the Geiger tube can be
broken by direct impact. Be careful not to let anything
penetrate the screen.
The Input/Output Ports
There are two ports on the left side of the Rad 100.
The cal
/probe input port (2) is used for calibrating electronically using a
pulse generator or an external IMI probe
“Calibrating
The output port (3) below the calibration input port allows you to
interface the Rad 100 to GeigerLink™, a USB interface for collecting,
displaying and sharing radiation data. This can also be used to
connect to a computer, data logger, earphones, or other device using
a 3.5 mm stereo plug. For more information, see “Interfacing to an
External Device” in Chapter 3.
Electronically” in Chapter 5.
. For more information, see
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3 Operation
The guidelines in this chapter describe how to use the Rad 100.
Units of Measurement
The Rad 100 is designed both for users of SI units (microsieverts per
hour and counts per minute) and for users of conventional units
(milliroentgens per hour and counts per minute). The default is
microsieverts per hour and counts per minute. To switch between units
of measurement, use the Utility Menu. See “The Utility Menu” in this
chapter.
Starting the Rad 100
Be sure that a standard 9-volt alkaline battery is installed in the
battery
Note: When installing the battery, place the battery wires along the side
of the battery and not under it.
To start the Rad 100, set the top switch to the mode you want, and
the bottom switch to On or Audio. The Rad 100 then does a
system check, displaying all the indicators and numbers.
After the system check, the radiation level is displayed in the
selected
beep
statis
When using the Rad 100, always be sure there is no obstruction between
the detector window and the source you are surveying
compartment in the lower rear of the Rad 100.
set
brief
mode. Ninety seconds after you start the Rad 100, a short
indicates that enough information has been collected to ensure
tical validity.
or
monitoring
.
Operating in the Dose and Count Rate Modes
When the mode switch is set to Dose Rate or Count Rate, the numeric
display is updated every three seconds. At low count rates, changes in
the radiation level displayed can take up to 90 seconds to stabilize. See
“Operating Ranges and Response Times” in this chapter for more
information.
Count Ra te (CPM) and timed total counts are the most direct
methods of measurement; Dose Rate (µSv/hr or mR/hr) measurements
Rad 100
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are calculated using a conversion factor optimized for Cesium-137, so this
mode is less accurate for other radionuclides unless you have calibrated
the instrument for a specific radionuclide using an appropriate source.
It is more appropriate to measure alpha and beta activity using Count
Rate rather than using Dose Rate. Conversion for alpha and beta
emitters is calculated differently, and the Rad 100’s Dose Rate reading
may not be accurate.
The most immediate indicators of the radiation level are the LCD and
the audio beep. It takes three seconds before an increase is shown on
the numeric display in Dose Rate mode.
Operating in Total/Timer Mode
When the mode switch is set to Total/Timer, the Rad 100 starts totaling
the counts it registers, and the numeric display is updated every second.
Taking a Timed Count
A timed total count is useful for determining the average counts per minute
over a period of time. The number of counts detected by the Rad 100
varies from minute to minute due to the random nature of radioactivity.
When a count is taken over a longer period, the average count per minute
is more accurate, and any small increase is more significant.
Taking an average allows you to detect low-level contamination or differences in background radiation due to altitude or soil mineral content,
and can be useful for educational purposes. For example, if one 10-minute
average is one count higher than another 10-minute average, the increase
may be due to normal variation. But over 12 hours, a one count increase
over the 12-hour background average is statistically signicant.
The Rad 100 can give you a total count for a timed period of from
one minute to 40 h
1.
With the Rad 100 operating, set the Mode switch to Total/Timer.
e display shows TOTAL.
2. Press the Set button twice in quick succession. e display shows SET,
the hourglass, and the most recent timing period used. e rst time
you use the timer, the setting is 24:00, which means 24 hours.
ours. Follow these steps:
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3. Use the + and – buttons to set the timing period. e timed period can be
for 1 to 10 minutes in one-minute increments, for 10 minutes to 2 hours
in ten-minute increments, or for 2 to 40 hours in one-hour increments.
4.
Press the Set button again to start the timed count. The Rad 100
beeps three times and starts counting. e hourglass indicator ashes
during the timed period.
During the counting period, if you want to see how much time remains, press and hold down the Set button. e display counts down
in hours and minutes to zero. For example, if the display says 00:21,
21 minutes remain.
5.
At the end of the timed period, the Rad 100 beeps three times,
and repeats the beeping several times. e number displayed is the
total count.
6. To display the average count and dose rates for the timed period, press
and hold the Set button. e display alternates between the average
count rate and the average dose rate every 3 seconds, and shows AVG
above the numeric display.
7. Press the Set button twice to return to normal operation.
Aer you start a timed count, the timer mode is active in the background
even when the Mode switch is set to Dose Rate or Count Rate. For
example, during and aer the timed period, you can switch back and
forth between Total/Timer and Dose Rate; when the timed period is
over, the total is displayed whenever you switch back to Total/Timer.
e hourglass indicator is shown on the display in any mode setting; it
is blinking while the timer is totaling counts.
Taking a Total Count
e timer can take timed counts of up to 40 hours. In certain situations,
you may want to take a total count without the timer; for example, taking
a count for longer than 40 hours. Follow these steps:
1.
Place the Rad 100 in the location where you plan
to take the count.
2. Note the time.
3. Immediately when you note the time, set the mode switch to Total/
Timer.
Rad 100
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4. At the end of the time period, note the time and the total on the
numeric display.
5. Subtract the starting time from the ending time to determine the
exact number of minutes in the timing period.
6. To get the average count, divide the total reading by the number of
minutes in the timing period.
Operating Ranges and Response Times
In some modes, when radiation levels increase over certain preset levels,
the Rad 100 uses autoranging, automatically changing to the X1000
scale. Whenever X1000 is
the displayed reading by 1000 to determine the radiation level. The
following table shows the radiation levels the Rad 100 measures in each
mode and how they are displayed.
Mode Regular Range x1000 Range
μSv/hr .000–1100 N/A
mR/hr .000–110 N/A
CPM 0–9999
CPS 0–3500 N/A
Total/Timer 0–9999
shown above the numeric display, multiply
10,000–350,000
(displayed as 10.00–350 with x1000 indicator)
10,000–9,999,000
(displayed as 10.00–9999 with x1000 indicator)
Maximum Level
When the maximum level for the current mode is reached, the Rad 100
beeps for three seconds, pauses for three seconds, and repeats that pattern.
The display shows RANGE:Full.
Full
icon continue until the level decreases or the Rad 100 is turned off.
The beeping pattern and the Range
Display Update and Response Time
In Total/Timer mode, the numeric display is updated each second. In the dose
and count rate modes, the numeric display is updated every three seconds.
When the radiation level is less than 1,000 CPM, the reading in the dose
and count rate modes is based on the radiation detected in the immediately
previous 90 seconds. In order to give a quicker response to changes, when
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Rad 100
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the radiation level exceeds 1,000 CPM in any 90-second period, the reading
is based on the previous 6 seconds, and when it exceeds 6,000 CPM, the
reading is based on the previous 3 seconds, as shown in the following
his automatic change in response time is called auto-averaging.
table.
T
Radiation Level
<1000 CPM or <8.3 μSv/hr or <.83 mR/
hr (<17 CPS)
1000–6000 CPM or 8.3–50 μSv/hr or .83–5 mR/
hr (17–100 CPS)
>6000 CPM or >50 μSv/hr or >5 mR/
hr (>100 CPS)
Basis for Reading
(after first 90 seconds)
90 seconds
6 seconds
3 seconds
Note: You can set the response time to 3 seconds at all radiation levels
using the Utility Menu; see “e Utility Menu” in this chapter.
Rad 100
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The Utility Menu
The Utility Menu allows you to change the default settings for several
operating parameters. When a setting is changed, it remains in effect
after the Rad 100 is turned off and until you change it again.
• To activate the Utility Menu, hold down the + button on the end panel
while you turn on the Rad 100. The word MENU appears at the
bottom right of the numeric display, and the display shows 1 for menu
option 1.
• To scroll through the menu, push the plus (+) and minus (–) buttons.
• To select an option, push the Set button.
• Once an option is selected, use the + and – buttons to scroll among
the settings.
• Aer you choose the setting you want, select option 0 to exit the Utility
Menu.
e options are:
0 Resume normal operation.
1 Auto Averaging. on (the default) selects Auto averaging; oFF selects
3-second (fast response) averaging at all radiation levels.
2 Units of measurement. CPM µSv/hr (the default) selects counts per
minute and microsieverts per hour; CPM mR/hr selects counts
per minute and milliroentgens per hour; CPS µSv/hr selects counts per
second and microsieverts per hour.
3 Cal 100 Reset. Automatically resets the calibration factor to 100.
4, 5, 6 Reserved for future options.
7 Cal Factor Adjust. Displays the current calibration factor, which
you can then adjust to the new factor you want. See “Calibration” in
Chapter 5.
8 Factory Default Reset. Automatically resets items 1, 2, and 3 to Auto
averaging, CPM and µSv/hr, and a Calibration Factor of 100
9 Revision #. Displays the firmware version number.
.
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Interfacing to an External Device
The lower output jack on the left side of the Rad 100 is a dual
min
iature jack that provides an audible click for use with a headset, or
a data output that can be used to drive external
to record the counts on a computer, data logger, or accumulating
counter. Use a 3.5 mm stereo plug to access this port.
The outputs provide a positive pulse (9 volt peak, 1 kOhm impedance)
each time the Geiger tube detects a count. At the ring of the plug, the
pulse is approximately 1 millisecond wide and is well suited for chart
recorders and audio inputs. The tip signal is approximately 80
microseconds wide and is suitable for high-speed counting and
RS-232 and USB adaptors.
devices. You can use it
Computer cables for USB or serial ports and accompanying software
available from IMI.
For 4.5V logic compatible output, externally connect a 1 kOhm resistor
from the output
b e plugged directly into the jack. For some types of headphones, external
volume control may be needed.
GeigerLink by IMI, GeigerGraph by Mineralab and other third party
data collection and sharing solutions are available for use with the
Rad 100. Visit IMI at http://medcom.com for more information.
Rad 100
13
to ground. A standard stereo or mono headphone can
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4 Common Procedures
e following sections give guidelines for several commonly-used pro
cedures. With any procedure, the user must determine the suitability
of the instrument or procedure for that application.
Establishing the Background Count
Normal background radiation levels vary at different locations, according
to altitude and other factors, such as types of minerals in the ground.
Levels vary at different distances from the ground, and may differ even
in different areas of the same room. To accurately interpret the readings
you get on the Rad 100, it is a good idea to establish the normal background radiation level for each area you plan to monitor. You can do this
with a timed count. Use the following steps to get a ten-minute average.
1.
With the Rad 100 operating, set the Mode switch to Total/Timer.
2. Press the Set button twice in quick succession.
3. e display shows the current timer period and SET. Unless you have
previously changed it, the display reads 24:00, which means 24 hours.
Use the + and – buttons to change the timer period to ten minutes.
4. Press the Set button on the end panel. The Rad 100 beeps three
times and starts counting.
During the timed count, if you want to see how much of the ten
minutes remains, hold down the Set button. e display counts down
from ten minutes to zero. For example, if the display says 00:03, seven
minutes have elapsed and three minutes remain.
5.
At the end of the ten minutes, the Rad 100 beeps three times,
and repeats the beeping several times. Note the total reading.
6. To nd the average count and dose rates, hold down the Set button.
A ten-minute average is moderately accurate. You can repeat it several
times to nd how close the averages are. To establish a more accurate
average, take a one-hour timed count. In some locations, you may want
to take a longer count (for example, 12 hours). If you need to
determine
locations
whether there is contamination, take averages in several
and compare the averages.
-
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For more information on using the timer, see “Taking a Timed Count”
in Chapter 3.
Environmental Area Monitoring
You can keep the Rad 100 in Dose Rate or Count Rate mode when
you want to monitor the ambient radiation, and look at it from time
time to check for elevated readings.
If you suspect an increase in ambient radiation, use the timer to take a
ten-minute count, and compare the average to your average background
co
unt. If you suspect an increase that is too small to detect with a short
timed reading, you can take a longer count (for example 6, 12, or 24 hours).
ever
to
Checking an Object
To check an object, place the Rad 100 next to
it with the end window facing and near the
object; otherwise you may miss alpha and
low-level beta radiation. To determine if an
object is slightly radioactive, place the Rad
100 next to it and take a timed count over
an appropriate period of time.
When not using the end window, hold the
Rad 100 so that the side wall of the tube is
as close as possible to the object. The best
position is with the top right corner of the
back of the Rad 100 closest to the object
Position of Geiger Tube
To measure as much as possible of the radioactivity of an object, place
the
Rad 100 as close as you can without touching the object. The
radiation level for gamma radiation from a localized source decreases
according to the inverse square law. If you move to twice the distance
from the object, the radiation drops by a factor of four.
Alpha
Window
Geiger
Tube
CAUTION: Never touch the Rad 100 to an object that may be
contaminated. You may contaminate the instrument. A contaminated instrument will not be accepted for repair or servicing.
Rad 100
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5 Maintenance
The Rad 100 should be handled with care and can be calibrated as necessary
to comply with regulations. Use the following guidelines to maintain the
Rad 100 properly.
Calibration
The Rad 100’s readings typically remain stable for many years of use.
Specific industries, such as diagnostic laboratories, radiography, and
public safety, operate under standards or regulations that require routine
calibrations. In most regulated environments, an annual calibration meets
these standards. Some standards require more frequent calibrations, and
some also require the occasional u se of a check source to make sure the
instrument is working properly. For a recommended laboratory for
instrument calibration, see the International Medcom, Inc. website at
medcom.com. Check-sources are available from various licensed
suppliers. Any radioactive source should be handled with caution and
shielded properly during storage.
e standard radionuclide for calibration is Cesium-137. To calibrate to
another radionuclide, use a calibrated source for that radionuclide or determine the appropriate conversion factor referenced to Cs-137. A certied test
range should be used. Depending on the facility, calibrations are typically
done at about two-thirds of the maximum reading, or 660 μSv/hr (66 mR/
hr). Some labs can do a three-point calibration check at, for example, 250,
500, and 660 μSv/hr (25, 50, and 66 mR/hr). Calibration should not be
done at levels below 10 μSv/hr (1mR/hr) or above 900 μSv/hr (90 mR/hr).
If no source is available, and the Geiger tube is functioning normally,
an electronic calibration can be performed using a calibrated pulse
generator. is conrms that the instrument is counting accurately, but
does not conrm the Geiger tube sensitivity.
Calibrating Using a Source
Most certified calibration laboratories utilize robotics to minimize
or
eliminate radiation exposure to the calibration personnel. The Rad
100’s calibration procedure is designed to further minimize exposure.
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Rad 100
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Before you calibrate the Rad 100, make sure the distance between the
Rad 100 and the source is correct to produce the appropriate dose
rate.
Follow these steps:
1.
Start with the Rad 100 turned off and the Mode switch set to
Dose Rate.
2. Hold down the – button on the end panel while you turn the On/
O/Audio switch to On. (Don’t use the Audio setting.)
The display shows CAL, and the Rad 100 counts down for 15
seconds, beeping each second. This delay gives you a chance to move
out of the field and then expose the source. At the end of the 15 seconds, the Rad 100 beeps several times.
3.
The Rad 100 collects data for 90 seconds, beeping as it does so,
with CAL and the hourglass indicator ashing. At the end of the 90
s, it beeps several times. e display shows CAL and SET. Yo u
second
can now seal or close the source.
4. Press the + and – buttons to adjust the reading to what it should be.
When the reading is correct, press the Set button. e new calibration
factor is automatically calculated from the adjustment you make.
5.
The new calibration factor is displayed for several seconds, then the
Rad 100 beeps and resumes regular operation.
e calibration factor is set to 100 (percent) at the factory. If you change
the reading, for example, to 20% higher than the factory reading, the
new calibration factor would be 120. The current calibration factor is
dis
played during the system check when the Rad 100 is first turned on.
Calibrating Electronically
You can calibrate the Rad 100 electronically using a pulse or function
generator. Electronic calibration requires a cable with a 2.5 mm plug,
with the tip carrying the signal. Follow these steps:
1.
Set the signal height amplitude to 3.3 volts (positive pulse).
2. Plug the cable into the upper jack.
Rad 100
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3.
Start with the Rad 100 turned off and the Mode switch set to Dose
Rate. Hold down the – button on the end panel while you turn the
On/Off/Audio switch to On. (Don’t use the Audio setting.)
The display shows CAL, and the Rad 100 counts down for 15 seconds,
chirping each second. At the end of the 15 seconds, the Rad 100
beeps several times.
4.
The Rad 100 collects data for 90 seconds, beeping as it does so,
with CAL and the hourglass indicator ashing. At the end of the 90
seconds, it beeps several times. e display shows CAL and SET.
5.
Use the following table to check the Rad 100’s accuracy. The table
shows appropriate pulse generator count rates to calibrate for Cs-137.
If the accuracy is not within desired limits, follow step 6. Note that
the Rad 100 automatically compensates for lost counts due to
tube dead time. Thus, the display reading in CPM mode does not
equal the input frequency. You can display uncompensated counts
in CPM mode by continuously holding down the – (minus) button;
ading now corresponds to the input frequency.
the re
Pulse Generator Input Display
Hz Pulse/min CPM μSv/hr mR/hr CPS
162.97 9778 12,000 100 10 200
318.88 19133 24,000 200 20 400
748.50 44910 60,000 500 50 1,000
1128.67 67720 96,000 800 80 1,600
1358.70 81522 120,000 1,000 100 2,000
GM
6. Press the + and – buttons to adjust the reading to what it should be.
When the reading is correct, press the Set button. e new calibration
factor is automatically calculated from the adjustment you make.
7. e new calibration factor is displayed for several seconds, then the
Rad 100 beeps and resumes regular operation.
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Rad 100
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Troubleshooting and Service
The Rad 100 is a highly reliable instrument. If it does not seem to be
working properly, look through the following chart to see if you can
identify the problem.
Problem Possible Cause What to Check
Display is blank
Display works,
but no counts
are registered
Reading is high,
but another
instrument has
a normal reading in the same
location
Battery: dead, missing,
or poor connection
Damaged Geiger tube If the mica surface of the tube has
Contamination
Moisture
Photosensitivity Remove from direct sunlight and
Continuous discharge
Electromagnetic
interference
Install and firmly connect a
new 9-volt alkaline battery
visible breaks or wrinkles, it needs
to be replaced
Scan the Rad 100 with another
instrument; clean the instrument
with a damp cloth and mild
detergent
The circuit board may be wet; dry
the instrument in a warm dry place;
if it still has a problem,
factory service
ultraviolet sources;
count drops, the mica coating on
the Geiger tube may be coming
off and the tube needs to be
replaced
The Geiger tube needs to be replaced
Move the instrument away from
sources of extremely high-energy
non-ionizing radiation, e.g.,
electro-magnetic or microwave
it requires
if the high
Rad 100
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If the Rad 100 requires servicing, please contact your distributor or
International Medcom, Inc. for instructions on where to ship the
instrument.
Contact IMI at 707-823-0336 or at [email protected].
Do not attempt to repair the Rad 100; it contains no user-serviceable
parts and you could void your warranty.
CAUTION: Do not send a contaminated instrument for repair
under any circumstances. Contact IMI for support.
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Rad 100
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6 Basics of Radiation and Its Measurement
is chapter briey tells what radiation is and how it is measured. is
information is provided for users who are not already familiar with
the
subject. It is helpful in understanding how the Rad 100 works and
in interpreting your readings.
Ionizing Radiation
Ionizing radiation is radiation that changes the structure of individual
atoms by ionizing them. e ions produced in turn ionize more atoms.
Substances that produce ionizing radiation are called radioactive.
Radioactivity is a natural phenomenon. Nuclear reactions take place
continuously on the sun and all other stars. e emitted radiation travels
through space, and a small fraction reaches the Earth. Natural sources of
ionizing radiation also exist in the ground. The most common of
these are uranium, radium, thorium and their decay products.
Ionizing radiation detected by the Rad 100 can be categorized into
four types:
X-rays are usually man-made radiation produced by bombarding a
metallic target with electrons at a high speed in a vacuum. X-rays are
electromagnetic radiation of the same nature as light waves and radio
waves, but at extremely short wavelength, less than 0.1 billionth of a
centimeter. ey are also called photons. e energy of X-rays is millions
of times greater than that of light and radio waves. Because of this high
energy level, X-rays penetrate a variety of materials, including body tissue.
Gamma rays occur in nature and are almost identical to X-rays, but
generally have a shorter wavelength than X-rays. Gamma rays are very
penetrating; thick lead shielding is generally required to stop them.
Beta radiation. A beta particle consists of an electron emitted from
an atom. It has mass so it generally doesn’t penetrate matter as deeply
as gamma and X-rays.
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Alpha radiation. An alpha particle consists of two protons and two
neutrons, the same as the nucleus of a helium atom. It generally can
travel no more than 1 to 3 inches in air before stopping, and can be
stopped by a piece of paper.
When an atom emits an alpha or beta particle or a gamma ray, it
becomes a dierent type of atom. Radioactive substances may go
through several stages of decay before they change into a stable, or
non-radioactive, form.
An element may have several forms, or isotopes. A radioactive form of
an element is called a radioisotope or radionuclide. Each radionuclide
has a half-life, which is the time required for half of a quantity of the
material to decay.
Electron
Proton
Neutron
Hydrogen Tritium
A hydrogen atom has one electron
and one proton. The most common
isotope has no neutrons and is stable.
Tritium is a radioactive isotope of
hydrogen. It has two neutrons in
its nucleus.
The chart on the following page shows the complete decay chain
for
Uranium 238, which ends with a stable isotope of lead. Each
radionuclide decays to become other elements (referred to as
daughters or progeny). For example U-238 becomes Th-234, which
becomes Pa-234, etc. Notice that the
the chain range from 164 microseconds
22
half-life of the radionuclides in
to 4.5 billion years.
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Isotope Emits Half-life Product
Alpha
Cathode
U-238 alpha 4.5 billion years Th-234 Thorium
Th-234 beta 24.1 days Pa-234 Proactinium
Pa-234 beta 1.17 minutes U-234 Uranium
U-234 alpha 250,000 years Th-230 Thorium
Th-230 alpha 80,000 years Ra-226 Radium
Ra-226 alpha 1,602 years Rn-222 Radon
Rn-222 alpha 3.8 days Po-218 Polonium
Po-218 alpha 3 minutes Pb-214 Lead
Pb-214 beta 26.8 minutes Bi-214 Bismuth
Bi-214 beta 19.7 minutes Po-214 Polonium
Po-214 alpha 164 microseconds Pb-210 Lead
Pb-210 beta 21 years Bi-210 Bismuth
Bi-210 beta 5 days Po-210 Polonium
Po-210 alpha 138 days Pb-206 Lead
Measuring Radiation
Alpha, beta, gamma, and X-rays ionize material they strike or pass
through. e amount of radiation is generally determined by measuring
the resulting ionization.
The Geiger tube used in the Rad 100 consists of an anode (positive
electrode) positioned in the center of a tubular cathode (negative electrode) lled with a mixture of argon,
neon, and either chlorine or bromine
gases. e cathode is a thin-walled
metallic cylinder sealed at each end
with an insulating disk to contain the
gas. e anode is a wire that extends
into the cylinder. A high voltage is
applied to the electrodes to create an electrical eld within the chamber. When radiation passes through the chamber and ionizes the gas,
it
generates a pulse of current. The Rad 100 electronically processes
these pulses to display the radiation level.
Window
(Side Wall)
Anode
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Radiation Measurement Units
Several dierent units are used to measure radiation, exposure to radiation, and dosage.
A roentgen is the amount of X-radiation or gamma radiation that produces one electrostatic unit of charge in one cc of dry air at 0° C and
760 mm of mercury atmospheric pressure. The Rad 100 displays
readings in milliroentgens per hour (mR/hr). A milliroentgen is one
one-thousandth of a roentgen.
A rad is the unit of exposure to ionizing radiation equal to an energy
of 100 ergs per gram of irradiated material. is is approximately equal
to 1.07 roentgen.
A rem is the dosage received from exposure to a rad. It is the number
of rads multiplied by the quality factor of the particular source of radiation. e rem and millirem (one one-thousandth of a rem) are the
most commonly-used measurement units of radiation dose in the U.S.
One rem is generally considered to equal one rad.
A sievert is the standard international measurement of dose. One sievert
is equivalent to one hundred rems. A microsievert (µSv) is one millionth
of a sievert.
A curie is the amount of radioactive material that decays at the rate of
37 billion disintegrations per second, approximately the decay rate of
one gram of radium. Microcuries (millionths of a curie) and picocuries
(trillionths of a curie) are also oen used as units of measurement.
A becquerel (Bq) is equivalent to one disintegration per second.
Higher Than Normal Readings
Due to the random nature of radioactivity, the Rad 100 reading
varies from minute to minute.
Normal radiation levels in dierent locations can vary greatly due to
soil composition, altitude, and other factors. For example, normal background at 10,000
24
feet might be double that at sea level. On an airplane,
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the radiation at 35,000 to 40,000 feet may be as much as 30 to 50 times
the normal level on the ground.
Granite counter tops and other natural sources of radiation can
affect your readings. Once you get accustomed to what can be
normally expected in various situations, it becomes relatively easy to
see activity that is outside the range of what is normal. If you have
questions about your readings please contact IMI at 707-823-0336
or, [email protected].
Follow our blog at geigercounter.com and subscribe to our mailing
list there to get the latest up-to-date information on radiation
detection. We respect your privacy and will not share your email
address with others.
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Appendix: Technical Specifications
Detector:
Halogen-quenched Geiger-Mueller detector (LND 712)
Mica end window density is 1.5–2.0 mg/cm
2
Side wall is 0.012" #446 stainless steel
Detects Alpha, Beta, Gamma, and X-radiation
Display:
Operating Range:
4-digit liquid crystal display with mode indicators
µSv/hr: .000 to 1,100
mR/hr: .000 to 110
CPM: 0 to 350,000
CPS: 0 to 3,500
Total: 0 to 9,999,000 counts
Calibration:
Gamma Sensitivity:
8
7
6
5
4
3
Relative Response
2
Window
1
0
1.00E+01 1.00E+02 1.00E+03 1.00E+04
Cesium-137 (gamma)
1,000 CPM/mR/hr referenced to Cs-137
ENERGY RESPONSE CURVE
Side
Energy (KeV)
Accuracy:
Timer:
Averaging Periods:
26
±10% typical; ±15% maximum
Can set sampling periods of 1 minute to 40 hours
Display updates every 3 seconds, showing the
average for the past 90-second time period at normal levels. e averaging period decreases as the
radiation level increases.
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Count Light:
Audio:
Ports:
Red LED ashes with each count
Beeper chirps for each count (can be muted)
• Output: Stereo 3.5 mm jack sends counts to computers, data loggers, other CMOS-compatible devices,
earphones, and educational data collection systems.
0–9 V, 1 kOhm impedance.
• Input: 2.5 mm mono jack provides calibration input.
0–3.3 V, > 5 µs width, rising edge triggered.
Anti-Saturation:
Readout holds at full scale in elds up to 100 times
the maximum reading
Temperature Range:
Power:
-20° to +50° C , -4° to +122° F
One 9-volt alkaline battery; battery life 2,000
hours typical, 700 hours minimum at normal
background radiation levels at sea level. Battery life
decreases as radiation level rises.
Size:
Weight:
Options:
Certifications:
150 x 80 x 30 mm (5.9" x 3.2" x 1.2")
225 grams (8 oz) including battery
Computer soware and cable available
Certied:
Emissions: EN 55011:2009 +A1:2010 (Class B
emissions limits); EN 61326-1:2006 (Class B) RF
Emissions
Immunity: EN 61326-1:2006 (Annex C) Portable
Test and Measurement Equipment; EN 61000-42:1995 (ESD); EN 61000-4-3:1997 (EM)
RoHS Compliant
Meets WEEE standards
Specications subject to change without notice.
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Limited Warranty
This product is warranted to the original owner to be free from
defects in materials and workmanship for two years from the
date of purchase with the exception of the Geiger-Mueller
tube, which is warranted for one year. The battery is not
included in this warranty. IMI-International Medcom, Inc.
will, at its own discretion, repair or replace this instrument if
it fails to operate properly within this warranty period
provided that it has not been subjected to misuse, abuse, or
neglect. Modification or repair of this instrument by anyone
other than IMI voids this warranty.
Contamination of this instrument with radioactive materials
voids this warranty. Contaminated instruments will not be
accepted for servicing at our repair facility.
The user is responsible for determining the suitability of this
product for the intended application. The user assumes all risk
and liability connected with such use, IMI is not responsible
for incidental or consequential damages arising from the use
of this instrument.
The terms of this warranty are subject to change without notice.
IMI-International Medcom, Inc.
103 Morris Street, Suite A-5
Sebastopol, CA 95472
Phone Toll Free: (877) 378-1010
(707) 823-0336
Fax: (707) 823-7207
customercare@medcom.com
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Rad 100
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