Images Scientific Instruments GCA-07 Series Geiger Counter User Guide
- September 21, 2024
- Images Scientific Instruments
Table of Contents
GCA-07 Series Geiger Counter
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Product Information
Specifications:
-
Radiation Detected: Alpha, Beta, Gamma, and X-Rays
-
Detector: Geiger-Muller tube Ne + Halogen filled with a .38
effective diameter 1.5-2.0 mg/cm2 mica end window -
Detector Sensitivity: Alpha above 3.0 MeV, Beta above 50 KeV,
Gamma above 7 KeV -
Countable Pulse Range: 1 (CPM) – 10000 + counts per second
(CPS) -
Converted Radiation Range: .05 mR/hr – 1000 mR/hr (Imperial),
.0005 mSv/hr – 10.0 mSv/hr (SI Metric)
Features:
-
Internal Geiger Mueller tube for model GCA-07
-
External wand with Geiger Mueller tube for model GCA-07W
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Calibrated and certified accurate in reading radiation levels
to within 5% -
LCD Display: 16 character by 2 line with backlight switch
Product Usage Instructions
Main Panel Controls:
The main panel controls include the LCD display, backlight
switch, and low battery indicator. The LCD display provides
real-time counts per second or counts per minute on the first line
and converted radiation levels on the second line.
Operation:
The Digital Geiger Counter has various modes including Survey
Meter Modes, USB/TTL Adapter, and Graphing Software. Make sure to
select the appropriate mode for your intended use.
Setting Jumpers / Contrast Control:
In the Appendix section of the manual, you can find information
on setting jumpers and adjusting the contrast control for optimal
performance.
Technical Specifications:
Refer to the Technical Specifications section for detailed
information on the detector sensitivity, pulse range, and radiation
detection capabilities of the device.
FAQ
Q: How do I know when to change the battery?
A: The LED marked Low Battery will turn on when the battery
power drops to approximately 7 Volts, indicating that it’s time to
change the battery. It is recommended to change the battery when
the low battery indicator is on to ensure accurate readings.
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Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . 3 Features . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . 4 Main Panel Controls . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . 5
2. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . 6 Survey Meter Modes . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 USB/TTL Adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 7 Graphing Software . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Geiger Counter and Radiation Basics . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . 11 Radioactivity . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Geiger
Muller Tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . 11 Count Rate Vs Dose Rate . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Measurement of
Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . 13 How Much Radiation is Safe? . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . 14 Checking for Radiation . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Finding Radioactive Sources. . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . 16 Separating and Detecting Alpha, Beta & Gamma . . .
. . . . . . . . . . . . . . . . . . . 16 NIST Calibration / NRC Certification
and Why It’s Important . . . . . . . . . . . . 17
4. Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . 18 Setting Jumpers / Contrast
Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Technical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . .19
Warranty
1. Introduction
The model GCA-07 has an internal Geiger Mueller tube. The model GCA-07W uses
an external wand that houses the Geiger Mueller tube.
Scientific Instrument & Industrial Tool
Our Digital Geiger counters have been calibrated and certified accurate in
reading radiation levels to within 5% from background radiation to 1000 mR/hr.
NRC Certification available at additional cost.
Perfect for schools and industry. In the laboratory the Digital Geiger Counter
may be used to conduct nuclear experiments and measurements. Free Windows 7
graphing programs. Graphic Files may be exported to Excel spreadsheets.
Communication specifications are provided for users to read the output of the
Geiger Counter and write their own programs.
Applications
- Education – Classroom demonstrations and experiments Emergency Services and Domestic Preparedness HAZMAT and Compliance Verification * Dirty Bomb Screening and EMT’s
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GCA-07
Nuclear Experiments Online
Images Scientific Instruments publishes a number of nuclear experiments you
can perform with you digital Geiger counter. Experiments are suitable for
schools, teachers and students. Visit our website at:
http://www.imagesco.com/geiger/nuclear_experiments/experiment1.html
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Features
Radiation Detected Alpha, Beta, Gamma and X-Rays.
Detector Geiger-Muller tube Ne + Halogen filled with a .38″ effective diameter
1.5-2.0 mg/cm2 mica end win-
dow.
Detector Sensitivity Alpha above 3.0 MeV Beta above 50 KeV Gamma above 7 KeV
Countable Pulse Range Converted Radiation Range
1 (CPM) – 10000 + counts per second (CPS) .05 mR/hr – 1000 mR/hr (Imperial) .0005 mSv/hr – 10.0 mSv/hr (SI Metric)
The Liquid Crystal Display (LCD) is 16 character by 2 line that provides an
easy to read output, see image to right. LCD has an on-off backlight switch .
LCD display continuously updates counts per second (or counts per minute) on
line one while displaying converted radiation level second line.
Backlight Switch turns on and off the LCD backlight,. The LED marked Low
Battery will turn on when the battery power drops to approximately 7 Volts to
alert the user to change battery. Readings taken when low battery indicator is
on may not be accurate.
The LED marked Pulse–is a secondary radioactive particle indicator it blinks
each time a radioactive particle is detected by the Geiger Counter. The Power
Switch turns power on or off to the GCA-07. The Speaker Switch turns the sound
on or off to the internal speaker. The speaker is a secondary radioactive
particle indicator. It clicks each time a radioactive particle is detected.
Note: Plugging a headphone in the headphone jack will automatically turn off
the internal speaker.
Headphone jack is a standard 3.5mm for private listening. Using a headphone
automatically turns off the internal speaker of the Geiger counter.
External power jack is available for extended readings where battery operation
may not be practical. Power jack is 2.5mm x 5.5mm. Power input is 9VDC or 9VAC
@ 200mA min. current. Mobile operation uses a 9V battery. TTL Serial output
for PC available via 3.5MM stereo connector. Both the GCA-07 and GCA-07W
output the counts per second.
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Images SI, Inc.
Main Panel Controls
The first panel switch starting from the left selects whether the radiation
levels are shown in Systems International (SI) metric (mSv/hr) or imperial
(mR/hr) measurements.
The middle switch labeled CPS, AVG CPS and CPM selects one of the three Survey
Meter Modes:
CPS (Counts Per Second) is a one second counting mode. Real time radiation
readings and displays the count/second and equivalent radiation level in
either mR/hr or mSv/hr.
AVG CPS is a three second average of the CPS. AVG CPS performs a smoothing
function similar to analog meter readings. Displays the 3 Second CPS and
equivalent radiation level in either mR/hr or mSv/hr.
CPM (Counts Per Minute) is a one minute counting mode for measuring low levels
of radioactivity and
background radiation: Displays accumulated count and equivalent background
radiation in either uR/hr or uSv/hr. If radiation level is significant
radiation level is displayed either mR/hr or mSv/hr.
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2. Operation
Survey Meter Modes
CPS Mode: Set the Conversion switch to mR/hr (milliroentgen/hour). The time
function switch to
“CPS”, Backlight switch on and the audio switch on. Turn on the Geiger
counter. If you have a radioactive source bring the source close to the GM
tube. For Geiger counters with an external wand, bring the wand close to the
radioactive source.
Every radioactive particle detected will cause the Geiger counter to click and
the LED to blink. The LCD digital display in this mode updates the count and
radiation level every second, see photo above. The display always shows the
previous seconds count and radiation level. The count “Count/Sec” is the
number of radioactive particles detected in the previous second. On the second
line the equivalent radiation level of that count in mR/hr. You can change the
Conversion switch to mSv/hr to read the radiation level in milli-
sieverts/hour.
3-Second Average: The three second average of the CPS. AVG CPS performs a
smoothing function
similar to analog meter readings. Displays the 3 Second CPS and equivalent
radiation level in either mR/hr or mSv/hr.
CPM Mode
The CPM mode displays the counts per minute and convert the radiation level
into micro-Roentgens (uR/ hr) or micro-Sieverts (uSv/hr). The CPM modes is
useful for checking background radiation. First set the switch to Metric or
Imperial measurement. Next set the time function switch to CPM. The LCD
display changes. The left side of the first line begins a count up to 60
seconds, increasing by 1 each second. The right hand side of the first line
displays the number of radioactive particles detected.
At the end of the CPM count the Digital Geiger counter will display the total
CPM and equivalent radia-
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Images SI, Inc.
tion level for one second before beginning another CPM counting cycle.
If you changed to the 1 minute time from 1 second the second line will display
the radiation level last calculated from the previous mode. If the Geiger
counter is turned on in the 1 minute mode the second line will display the
word “Initializing” for the first 60 seconds.
USB /TTL Cable Adapter (sold separately)
Serial data consisting of the CPS counts may be read by a Windows PC computer
using a USB/TTL Serial Cable, included. USB TTL Serial Cable allow easy
interfacing of the GCA-07 via USB. The cable has a USB connector on one end
that plugs into PC, and a 3.5mm stereo jack that plugs into the GCA-07.
3.5mm audio jack output configuration: · tip – TxD · ring – RxD
· sleeve – GND *See page 18 for changing data output to jack’s Tip or Ring.
Useful for using 3rd party TTL Serial/ USB cables.
Digital Geiger Counter Graphing Software
We offer a Windows PC program that reads this serial information for
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charting and recording the measured radiation over time (see screenshot
below).
A free lite version of our Geiger graphing software can be downloaded at:
www.imagesco.com/geiger/geiger-graph.html
The Radiation Monitoring and Graphing software is useful for monitoring
radiation. The software constantly monitors for the Counts Per Second (CPS)
values and plots them on the Graph when connected to one of our Digital Geiger
Counters. It calculates radiation levels from incoming serial data and plots
them along with the CPS values. The software is capable of capturing values
for different time units (i.e., Sec-
onds, Minutes, Hours or Days). The recorded data can be saved, and exported as a CSV delimited file for use in various other applications including Word & Excel. Data can be displayed as 1 of 4 types of graphs. One can also set alarm levels for CPS/Radiation Levels. If the values cross the specified levels, the software issues a visual and an audible alert.
Installing the Software Package
Begin by installing the appropriate drivers for the USB/TTL cable included
with the purchase of the software program and/or cable. These drivers may also
be downloaded from the Images website at:
http://www.imagesco.com/semiconductors/usb-3.5mm.html
Once the drivers are installed, restart your computer and then plug the cable
into an available USB port.
Now install the Windows Geiger counter program on your computer. The digital
Geiger counter has TTL serial output. Connect the Geiger counter to the
computers serial port using the USB TTL serial cable. Make sure the serial/TTL
jumper is set to serial, see “Setting the Back Jumpers/Contrast Control” in
the Appendix.
When opening the application, make sure the program’s COM port is set to the
correct COM port where the USB cable and Geiger counter has been connected. A
troubleshooting guide for the com port is also included in the Appendix.
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Images SI, Inc.
The Geiger counter must be on and connected to the computer for the program to
begin graphing. To begin graphing simply click “Start” in the lower left hand
corner of the main interface screen.
The main program interface is comprised of the following components:
· The main graph on which the values will be plotted.
· Time options frame. This allows user to select different time units (Second,
Minute, Hour, Day) For example, if you set the time unit to Second, then the
program will count the radiation levels per second, and plot. If you set it to
Minute, the program will count radiation levels per minute, and plot.
· Graph type frame. This allows user to switch between different views of
graph (Line Chart, 3D Line Chart, Bar Chart and 3D Bar Chart).
· Plot frame. This comprises of the Start button which starts the capturing
and plotting process. When capturing is in progress, the same button will act
as a Stop button, which stops capturing and plotting process.
· Graph frame. This comprises of a Clear button which clears the graph, a Save
button which saves values to the active file, a Save As button which allows to
select a different file for saving, and Viewer button which launches the
Viewer.
· mR/hr frame. This comprises of a textbox which displays current radiation
level.
· Serial Port frame. This comprises of a combo box which allows com port
selection.
· Status frame. This comprises of an LED which displays the status of the
program. The status LED changes according to the activity. When no capturing
is in progress, the LED will be Off and status will be Stopped. When the
program is receiving values, the LED will be Blue and status will be Receive.
When program is writing the values, the LED will be Green and status will be
Write.
· Real Time Data frame. This frame displays various real time values such as
Counts Per Second (CPS), total accumulated count (if the program is running on
modes other than Second), time left before next update, and total number of
points captured.
· Others frame. This comprises of a Print Chart button which allows to prints
the current plot, a Settings button which opens the Settings dialog, an About
button which displays the information about the program, and an Exit button
which quits the program.
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The image below outlines where each frame is located and shows data being displayed as a line graph. The image on the previous page shows the data in a bar graph.
Writing Your Own Interface Software
It is possible to write your own software to read the data from the digital
Geiger counter. The data is outputted from a 3.5 MM stereo jack, as shown on
previous page. The +5V serial data is sent out as a two byte number (most
significant byte first) with the following specifications: 9600 Baud,
Inverted, 8 data bits, no parity and one stop bit.
The Serial Data Output is a two byte (8-bit) number every second that
represents the previous count per second. High byte is followed by the low
byte. Communication parameters are: 9600 Baud, Inverted, 8 data bits, no
parity and one stop bit. These parameters are for anyone wishing to read the
data from the Digital Geiger counter.
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Images SI, Inc.
3. Geiger Counter and Radiation Basics
Radioactivity
Radioactivity is the spontaneous emission of energy from the nucleus of
certain elements, most notably uranium. There are three forms of energy
associated with radioactivity; alpha, beta and gamma radiation. The
classifications were originally made according to the penetrating power of the
radiation. Alpha rays were found to be the nuclei of helium atoms, two protons
and two neutrons bound together. Alpha rays have a net positive charge. Alpha
particles have weak penetrating ability; a couple of inches of air or a few
sheets of paper can effectively block them. Beta rays were found to be
electrons, identical to the electrons found in atoms. Beta rays have a net
negative charge. Beta rays have a greater penetrating power than Alpha rays
and can penetrate 3mm of aluminum. Gamma rays are high-energy photons. This
has the greatest penetrating power being able to pass through several
centimeters of lead and still be detected on the other side.
Images Digital Geiger Counters are sensitive to all three types of
radioactivity.
The Geiger Mueller Tube
Geiger Mueller tubes are simple devices that detect and measure radioactivity.
The original design by H. Geiger and E.W. Mueller in 1928 hasn’t change very
much. The basic sensor functioning remain the same. A cutaway drawing of the
tube is shown below. The wall of the GM tube is a thin metal cylinder
(cathode) surrounding a center electrode (anode). It is constructed with a
thin Mica window on the front end. The thin mica window allows the passage and
detection of alpha particles. The tube is evacuated and filled with Neon,
Argon plus Halogen gas. It is interesting to see how the GM tube detects
radioactivity. A 500-volt potential is applied to the anode (center electrode)
through a ten mega-ohm current limiting resistor. To the cathode of the tube a
460-k ohm
GCA-07W
resistor is connected.
In the initial state the GM tube has a very high resistance. When a particle
passes through the GM tube, it ionizes the gas molecules in its path. This is
analogous to the vapor trail left in a cloud chamber by a particle. In the GM
tube, the electron liberated from the atom by the radioactive particle and the
positive ionized atom both move rapidly towards the high potential electrodes
of the GM tube. In doing so they collide with and ionize other gas atoms. This
creates a small conduction path allowing a momentary surge of electric current
to pass through the tube.
This momentary pulse of current appears as a small voltage pulse across R2.
The halogen gas quenches the ionization and returns the GM tube to its high
resistance state making it ready to detect radioactivity.
Count Rate vs Dose Rate
Each output pulse from the GM tube is a count. The counts per second give an
approximation of the strength of the radiation field. Below is the GM tube
used in the GCA-07’s response to a cesium-137 source.
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Images SI, Inc.
Measurement of Radiation
There are a few scales that one can use to measure radiation. Depending upon your application, one scale may be better than the others.
Radiation Measurements
Roentgen: Is the measurement of energy produced by Gamma or X-Ray radiation in a cubic centimeter of air. It is abbreviated with the capital “R”. One milliroentgen, abbreviated “mR” is one-thousandth of a roentgen. One microroentgen, abbreviated “uR” is one-millionth of a roentgen.
RAD: Radiation Absorbed Dose. Original measuring unit for expressing the absorption of all types of ionizing radiation (alpha, beta, gamma, neutrons, etc) into any medium. One rad is equivalent to the absorption of 100 ergs of energy per gram of absorbing tissue.
REM: Roentgen Equivalent Man is a measurement that correlates the dose of any radiation to the biological effect of that radiation. Since not all radiation has the same biological effect, the dosage is multiplied by a “quality factor” (Q). For example, a person receiving a dosage of gamma radiation will suffer much less damage than a person receiving the same dosage from alpha particles, by a factor of three. So alpha particles will cause three times more damage than gamma rays. Therefore, alpha radiation has a quality factor of three. Following is the Q factor for a few radiation types.
The difference between the rad and rem is that the rad is a measurement of the radiation absorbed by the material or tissue. The rem is a measurement of the biological effect of that absorbed radiation.
Radiation: Beta, Gamma and X-rays Thermal Neutrons Fast n, a, and protons Heavy and recoil nuclei
Quality Factor (Q) 1 3 10 20
For general purposes most physicists agree that the Roentgen, Rad and Rem may
be considered equivalent.
System International (SI) of Units
The System International of unit for radiation measurements is now the
official system of measurements. This system uses the “gray” (Gy) and “sivert”
(Sv) for absorbed dose and equivalent dose respectively.
The conversion from one system to another is simple:
1 Sv = 100 rem 1 mSv = 100 mR (mrem) 1 Gy = 100 rad 1mGy = 100 mrad
1 rem = .01 Sv 1 mR = .01 mSv 1 rad = .01 Gy 1 mrad = .01 mGy
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How Much Radiation is Safe?
In the United States, the U.S. Nuclear Regulatory Commission (NRC) determines
what radiation exposure level is considered safe. Occupational exposure for
worker is limited to 5000 mrem per year. For the
general population, the exposure is 500 mrem above background radiation in any
one year. However for long term, multi-year exposure, 100 mrem above
background radiation is the limit set per year.
Let’s extrapolate the 100 mrem number to an hourly radiation exposure rate.
There are 365 days/yr x 24 hr/day equals 8760 hours. Divide 100 mrem by 8760
hours equals .0114 mrem/hr or 11.4/hr microrem. This is an extremely low
radiation level. The background radiation in my lab hovers around 32 uR/hr. Am
I in trouble? No. Typically background radiation in the United States averages
300 mrem/yr, or 34 microrem/hr. The NRC specifications is for radiation above
this 34 urem/hr background radiation.
Notice that my lab readings are in microrad (uR/hr) and the exposure limit is
given in microrem (urem/hr). I do not know what type of radiation (a , b or y)
the geiger counter is reading in my lab at any particular instant, so I do not
know the Q factor of the radiation and therefore can not calculate the mrem.
However for general purposes I consider them the one and the same. Remember,
the digital geiger counters are calibrated using a Cs-137 radioactive source.
Therefore the highest accuracy in reading radiation levels will be from Cs-137
sources.
Common Radiation Exposure (General Population)
Background radiation consists of three sources; Cosmic radiation from the sun
and stars. Terrestrial radiation from low levels of uranium, thorium, and
their decay products in the soil, air and water.
Exposure Source
Flight from LA to NY Dental X-ray Chest X-ray Mammogram Background Radiation
Dose(conventional) Dose (SI)
1.5 mrem 9 mrem 10 mrem 70 mrem 620 mrem/year
.015 mSv .09 mSv 0.1 mSv 0.7 mSv 6.2 mSv/year
Internal radiation from radioactive potassium-40, carbon-14, lead-210, and
other isotopes found inside our bodies.
Because of the randomness of radioactivity, background radiation can vary from
minute to minute and place to place. In my corner of the world I have a
background radiation that triggers the counter 22-34 times a minute.
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Images SI, Inc.
Checking for Radiation
Our line of Digital Geiger Counters are extremely sensitive and will detect
and measure background radiation in addition to detecting and measuring
radioactivity above background radiation. To test for small increases in
radioactivity that may be present in food and other materials to cause a
increase in the background radiation one must first establish the background
radiation level. To obtain your normal background radiation reading take an
hour’s worth (60) of one minute readings. This is the CPM (counts per minute)
mode on the GCA-07W. With this data collected. I would add the 60 readings
together. I would then take that total and divide it by 60 to get an average
CPM reading. Next I would look through the 60 CPM readings and mark down the
highest count CPM reading, and the lowest count CPM reading. Those two CPM
numbers are your Max and Min. With this information, you can determine if the
background CPM radiation reading(s) are greater than your MAX CPM number. If
the readings are consistently greater, you can make a logical assumption that
there is an increase in background radiation. To see the percentage increase
you would subtract the average CPM number from your reading to see what the
increase in radiation is on average. To increase accuracy, you could also
average say five hours worth of data or 300 one minute CPM samples to obtain
the average CPM, Min CPM and Max CPM. In general the greater the number of
samples the greater the level of confidence. The CPM averages may be different
for day and night, so you may also want to collect background radiation data
for time variances. The optional Geiger Counter Graphing Software for Windows
PC (see page 8), also available on Amazon, ASIN: B00WAK68U4, will allow you to
collect, monitor and save this data from the GCA-07W easily. To run a test,
position the probe (or Geiger counter) very close to the top surface of the
material you are testing, and run the counter in its CPM mode to check for
radiation above your established background radiation.
Finding Consistency in Readings
Because of the randomness of radioactivity, your readings may vary from second
to second. To help “even out” the readings, the GCA-07 has a built in
“smoothing feature. This feature is activated by putting the center switch
into AVG CPS Mode. The read out will display a running 3 second average.
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Finding Radioactive Sources
The mantle in some Coleman lanterns are radioactive. Bring your Geiger counter
to a local hardware store and check them out.
Uranium ore from a mineral or a rock store should also emit sufficient
radiation to trigger the counter.
A more reliable source is to purchase a radioactive source. Small amounts of
radioactive materials are available for sale encased in 1 inch diameter by ¼”
thick plastic disks. The disks are available to the general public license
exempt. This material outputs radiation in the micro-curie range and has been
deemed by the Federal government as safe.
The cesium-137 is a good gamma ray source. The cesium 137 has a half-life of
30 years.
Radioactive uranium ore and radioactive isotopes are available for purchase
from Images Scientific Instruments. http://www.imagesco.com/geiger
/radioactive-sources.html
Separating & Detecting Alpha, Beta and Gamma
By placing shields of different materials in front of the GM tube we can
filter out some radiation. For instance placing a paper shield in front of the
GM tube will block all the Alpha radiation. The Geiger counter will now only
detect beta and gamma radiations. If we place a thin metal shield in front of
the GM tube that would effectively block the alpha and beta radiation,
allowing the detection of only gamma radiation.
Radiation Shields for wand are available here:
http://www.imagesco.com/geiger/shields.html
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Images SI, Inc.
NIST Calibration
We perform calibration of our digital Geiger counters with a Cs-137 source
chart against a calibration standard using an NIST traceable Cs-137 source. A
Factory Calibration Certificate is provided with each unit. Source number
available upon request.
NRC Certification and Why It is Important
While many Geiger counter manufacturers claim high accuracy for their Geiger
counter, it simply is not true. It is not enough to say an instrument is
calibrated, nor is it enough to say the Geiger counter has an accuracy of 1%,
5%, 10%, or 20% because anyone can say that! Why? Without a legitimate
reference to compare “claimed” accuracy too, a claim of accuracy is
meaningless. Fortunately, the United States Government has a license standard
for Geiger counter accuracy. This is a Nuclear Regulatory Commission (NRC)
certification for accuracy. NRC certification can only be performed by a
nuclear laboratory licensed by the United States Government to perform such
certifications. Without this certification, you cannot be sure of any claim
that a Geiger counter accuracy is valid. Below is a picture of an NRC
certification label for one of our Digital Geiger Counters. After NRC
certification, a certification label is attached to the Geiger counter and
this certification is valid for one full year. If a manufacturer states their
Geiger counter is accurate, ask, “Is your Geiger Counter NRC certified?” If
not, their Geiger counter probably cannot pass NRC certification. But many
times a representative will hedge their answer and state that the NRC
certification is expensive and is not “currently” offered as an option. Ask,
“If I purchase your model and send the unit out for NRC certification will it
pass? And if it fails NRC, can I return the Geiger counter for a refund?”
Their answer will tell you what you need to know to make a sound purchasing
decision. Images SI, Inc. entire line of Digital Geiger counters are capable
of receiving an NRC certification. This certification is available to our
customers at an additional cost. Please contact us at
1-800-230-4535 for more information.
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4. Appendix
Setting the Back Jumpers / Contrast Control
If it becomes necessary to adjust contrast control or to set internal jumpers:
Remove back cover of the GCA-07.
Contrast Control: The contrast control has been optimized for the best viewing
of the LCD screen. However, it may be changed using a small Philips
screwdriver to adjust the potentiometer shown in picture to left.
TTL Serial / TTL Pulse: The default setting is for the microcontroller to
output serial data for the PC Graphing Program. In some experiments you may
want the raw TTL pulses outputted for each radioactive particle detected. As
one would need for a Gamma Ray telescope experiment, coincidence detectors, or
random number generator. Jumpers: To change Serial Output to TTL pulses (or
vice versa,) set labeled jumper to TTL or Serial as shown in Picture to the
left.
Tip/Ring Adjustment : If one is using a different USB to TTL Serial cabled
adapter , it may be necessary to change the data output to the tip and ring of
the stereo plug. Data output to the stereo 3.5 MM jack may be changed to
Tip/Ring using labeled jumper shown in Picture to left.
The picture shows the default settings for these jumpers.
To Change / Install Battery:
Battery compartment is located on the lower back of the Geiger Counter case.
Turn Geiger Counter off.
Slide battery compartment lid open. Attach 9 Volt battery to battery clip.
Install 9 Volt battery into battery compartment. Slide cover back into place.
It is important to note that when using the external power supply, there is no
need for a 9V battery.
18
Images SI, Inc.
Digital Geiger Counter Technical Specifications
Radiation Detected
Alpha, Beta, X-Ray, and Gamma
Detector Type Detector Sensitivity
Geiger Muller tube Ne + Halogen filled: Mica end window has a .38″ effective
diameter , with a density of 1.5-2.0 mg/cm2
Alpha above 3.0 MeV Beta above 50 KeV Gamma above 7 KeV
Countable Pulse Resolution Range
1 Count Per Minute (CPM) – 5000 Counts Per Second (CPS)
Radiation Resolution & Range
1.0uR/hr – 1000 mR/hr .01uSv/hr – 10 mSv/hr
GCA-07W
Limited Warranty
Images SI, Inc. warrants this product to the original retail purchaser to be
free from defects in materials and workmanship for a period of 90 days of
purchase. The Geiger Muller tube is very fragile and is not included in this
warranty.
This warranty may be extended to a period of 1 year by registering the product
on our website at:
http://www.imagesco.com/reg.html
Registration must occur within 30 days of delivery.
Images SI, Inc. will, at its own discretion, repair or replace the Geiger
counter if it fails to operate properly within the warranty period provided
that it has not been subjected to misuse, abuse, or neglect. Modification or
repair by anyone other than Images SI, Inc. voids the warranty.
Repairs/Replacements will only be made when the customer properly packages and
returns the unit to our facility with prior authorization.
Contamination of the Geiger counter with radioactive materials voids the
warranty. Contaminated instruments will not be accepted for repair.
Images SI, Inc. will not be responsible for any incidental or consequential
damages arising from the use of this device.
References
Read User Manual Online (PDF format)
Read User Manual Online (PDF format) >>