GCK-01 Geiger Counter Kit Manual and Assembly Guide
Contents
1. e dd is 0e z CPM Background xlsx Microsoft Excel N Chart Tools e x Home REDEE Mem Ma Jaa ew _ Anab Den a IL zu Change Save As Switch Select mmm E z Move Chart Type Template Row Column Data z momar Chart Type Data Chart Layouts Chart Styles Location Chart 1 Fl A 5 D E F G H J K L M N P R E 278 277 28 09 20 279 278 28 09 20 280 279 28 09 20 281 280 28 09 20 282 281 28 09 20 283 282 28 09 20 284 283 28 09 20 S 285 284 28 09 20 286 285 28 09 20 29 P Ae AA PUTA 288 287 28 09 20 gt 289 288 28 09 20 4 9 290 289 28 09 20 10 291 290 28 09 20 292 291 28 09 20 5 4 293 292 28 09 20 294 293 28 09 20 0 295 294 28 09 20 297 296 28 09 20 298 297 28 09 20 299 298 28 09 20 E 300 M 4 EasyLog 0585 _____________________________________ Ready Average 16 1409396 Count 298 Sum 4810 alg JD a 4 Rer 2 aM Figure 19 18 DMAD Three accessories in one The Digital Meter Adaptor is a combination of three accessories see figure 20 Primarily it is a digital meter that counts the pulses per second CPS from the Geiger counter and gives you an equiva2. EasyLog USB For example Outside Temp Choose the mode of operation 7 Record events the time at which the input changes up 104 times per second Record state changes the time at which the input changes and the duration of the change up to twice per second Count events the number of events is recorded but no time or date information up to 100 times per second The next screen figure 15 select rising edge and Flash red LED on event 2 OFF Figure 15 Select which edge the logger uses as a trigger Rising edge a voltage going from low to high t Falling edge a voltage going from high to low Select between voltage triggering i e an external voltage or volt free contacts i e a relay Voltage triggering C Volt free contacts Flash red LED on event C On Limits event count to 20 times per second off 16 The next screen figure 16 is the voltage range While the device outputs 4 5 volts TTL the data logger loads down the output to about 2 8 volts So it s necessary to use the 0 3V range ue Select the input range that suits the application Voltage range Low trigger voltage High trigger voltage H 4 v g 3v 0 8V 2 0V C 0 5y LI 3 4V C pno q2y 3 2V 8 0V Nate The trigger voltages are the respective levels that must be met for the logger to consider a voltage high low
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4. 1 PJ108 P2 1 2N3904 Q2 1 TIP3055 QI alternate transistor H1061 25 2 1 VAW 1 1 8M ohms 14W 1 33 ohms 14W 2 100 K ohms 14W 1 100 ohms 14W 5 10K YAW 500K P36W Switch Toggle Switch Slide 1 Transformer Full Wave Bridge Rect LE33 TO92R LM339 DIPI4 7805 TO220 SPK R7 R3 R5 R2 R13 R4 R12 R8 R9 RIO RII R14 R6 91 S2 TI U3 U2 U4 Ul Piezo speaker Components that are sold separately GMT 01 GMT 02 GMT 06 Mini Step up transformer Geiger Counter PCB Radioactive Sources Uranium Ore 99 95 74 95 49 95 12 00 10 00 39 95 CS 137 Source 5 uCi CS 137 Source 10 901 Electronic Analog Meter Radiation Network Software 84 00 Drop shipped from different location 125 00 Drop shipped from different location 22 95 79 00 Order from Images Company 109 Woods of Arden Road Staten Island NY 10312 718 966 3694 Tele 718 966 3695 Fax on the Internet at http www imagesco com Helpful Links U S Nuclear Regulatory Commission 24 http www nrc gov CDC Center for Disease Control maintains a radiation emergency web site http www bt cdc gov radiation index asp clinicians Health Physics Society http www hps org U S Environmental Protection Agency http www epa gov radiation 25
5. 0 18 01 58 a Total Counts 18 795 Elapsed Minutes 1 081 z lv Make Beep Sound Radiation Map DBR Graphing Radiation Fie view Map Layers Monitoring Stations GoTo Search Tools Help B Actual Level Bl Alert Level Monitoring Stations Remote Sim _Alert Mineralab 2004 linch 500 2 miles Cit 37 Stations at 21 CPM Draw Time 0 48 sec Zoom 1 2 Time Identifying Criteria John lovine Images Sl New York NY US 0 feet Other 4 16 2011 start GeigerGraph Adobe Photoshop 19 For those who want to join the Radiation Network http www radiationnetwork com the software and hardware is compatible with our Geiger Counter The radiation software is sold with an adapter cable see figures 22 and 23 The 3 5MM plug plugs into the same socket used by the DMAD adapter Figure 23 Analog Meter A electronic analog meter adds versatility to the Geiger Counter device by providing a visual indication of the intensity of the radiation field The analog meter is set up with a three position single pole switch For the LND 712 the ranges available are 0 1 mR hr 0 10 mR hr and 0 100mR hr For the GMT 02 the ranges available are 0 1 mR hr 0 10 mR hr and 0 50mR hr The analog meter requires a 5Volt power supply that we can obtain off the board The input to the meter is connected to one of the digital outputs and the ground to the meter circuit connects to Geiger counter ground The schematic
6. The next screen figure 17 15 the time increment Remember the data logger can count up to 32 510 events in a time increment with a maximum data rate of 100 events per second with the LED off I choose a one minute increment e Help 17 Figur Bil Options Tick the box below to count the number of events user specified time period e g the number of events every 10 seconds If left un ticked the logger will count the number of events over the entire logging period Enable counts per time period Hours Minutes Seconds Time period 1 3 The next few screens are self explanatory Connecting the Data Logger to the Geiger Counter The Datalogger has two alligator clip wires we attach the Geiger Counter s digital output too The red wire connects to one of the digital outputs and the black ground wire attaches to the circuit ground see figure 18 17 DURACELL PRO Figure 18 Once your data is recorded you reconnect the Logger to the computer and save the recorded test data as a text file I recorded 298 minutes of background data The instructions to import the text data into an Excel spread sheet are provided in the Data Logger instructions Once the data is inputted into Excel it can be manipulated and graphed see figure 19 below The average Count Per Minute CPM was 16 with a min count of 6 CPM and a maximum of 28 CMP
7. 6 beta y gamma Aluminum Lead Penetration Power of Radiation Figure 1 Alpha rays are 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 Thick lead is needed to attenuate gamma radiation Geiger Mueller Tube Geiger Mueller tubes are simple devices that detect and measure the intensity of radioactivity The original design by H Geiger and Mueller in 1928 hasn t changed very much The basic sensor functioning remains the same A cut away drawing of a typical Geiger Mueller GM tube is shown in figure 2 The wall of the GM tube is a thin metal cathode cylinder surrounding a center electrode anode The metal wall of the GM tube serves as the cathode of the GM Tube The front of the tube is a thin Mica window sealed to the metal cylinder The thin mica window allows the passage and detection of the weak penetrating alpha particles The GM t
8. L 1 j L j net L I1 j s ieee E _ L iss L I1 j as e ae E 1000 10000 Dose rate mR h Figure 3 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 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
9. Mount and solder diodes D1 through to D11 Make sure to orientate the line on the diodes with the line on the silk screen diode drawing on the printed circuit board DI D2 D4 D5 and 1N4007 D7 5 1V Zener D8 100V Zener 10 D9 and D10 200V Zener See text D11 LED The longer lead on LED 011 is the positive lead Make sure the positive lead is inserted into the pad toward the bottom of the pc board on the round side of the silk screen LED outline Next mount and solder the 14 pin IC socket see figure 7 Figure 7 In addition to adjusting the resistors to the GM tube you can also adjust the voltage to the GM tube Depending upon the zener diodes used you can vary the voltage between 400 and 600 volts The zener diodes D8 D9 and D10 to provide the regulation of the voltage delivered to the GM Tube The zener diodes provided with the kit are D8 100 volts D9 and D10 200 volts With this diode set you can vary the voltage to either 400 volts or 500 volts to the GM tube Keeping jumper J1 open will provide 500 VDC to the GM tube Shorting jumper J1 shorts out diode D8 and provides 400 VDC to the GM tube If you required 600 VDC diodes D8 to 010 ought to be made 200 zener diodes Keeping jumper J1 open provides 500 VDC to the GM tube Shorting jumper J1 shorts out diode D8 and provides 400 VDC to the GM tube Next install the regulator 7805 and the 3055 or H1061 transistor Insert components o
10. factor of three Following is the Q factor for a few radiation types Radiation Quality Factor Q Beta Gamma and X rays 1 Thermal Neutrons Fast n a and protons 10 Heavy and recoil nuclei 20 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 For general purposes most physicists agree that the Roentgen Rad and Rem may be considered equivalent The curie is a unit of radioactivity its symbol C1 It is defined by the amount radioactive decays per second 3 7 x 10710 decays per second When you purchase a radioactive isotope source it will be rate in microcuries uCi one millionth of a curie 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 01 Sv 1 mSv 100 mR mrem mR 01 mSv 1 Gy 100rad 1 rad 01 Gy ImGy 100 mrad 1 mrad 01 mGy The SI derivative of the curie is the becquerel Bq pronounced be ko rel which equals one decay per second How Much Radiation is Safe In the United States the U S Nuclear Regulatory Commission NRC determines what radiation exposure l
11. mSv Dental X ray 0 mrem 09 mSv Chest X ray 10 mrem 0 1 mSv Mammogram 70 mrem 0 7 mSv Background Radiation 620 mrem year 6 2 mS v year 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 Internal radiation from radioactive potassium 40 carbon 14 lead 210 and other isotopes found inside our bodies Testing for Radioactive Contamination For this test to be as sensitive as possible it is recommended that the GM tube be sensitive to alpha beta and gamma radiation Geiger counters can only test for gross radioactive contamination levels that will show up above background radiation levels Low level radioactive contamination may be effectively hidden within the natural noise of background radiation and not discernable using a Geiger counter Therefore for low level radioactive contamination Geiger counters are not the proper test instruments With this disclaimer in place this is the procedure to test for radioactive contamination that presents a increase in the background radiation Step one first establish the background radiation level establish background radioactivity level record the pulses Counts received per minute CPM The greater the number of minutes you count the more accurate will be you background radiation reading Average the CPM reading to determine a approximate backgro
12. Images Scientific Instruments Inc 109 Woods of Arden Road staten Island NY 10312 718 966 3694 Tel 718 966 3695 Fax www imagesco com GCK 01 Geiger Counter Kit Manual and Assembly Guide This kit can utilize a variety of GM tubes so depending upon tube s availability you can choose one that is readily available and in your price range Once assembled this Geiger counter outputs audible click and will blink a LED with each radioactive particle it detects In addition it has two digital outputs that may be connected to a number of accessory instruments a data logger Digital Meter adaptor that outputs an approximate radiation level RS 232 adaptor to plot radioactivity on a PC and true random number generator in addition to an analog meter adaptor that can approximate 3 radiation ranges 0 to 1 mR hr 0 10 mR hr and 0 100 mR hr This assembled Geiger counter is compatible to the Radiation Network software What is Radioactivity Radioactivity 1s the spontaneous emission of energy from the nucleus of certain atoms The most familiar radioactive material is uranium There are three forms of energy associated with radioactivity alpha beta and gamma radiation The classifications were originally determined according to the penetrating power of the radiation see figure 1 Depending upon your GM tube selection our Geiger counter can detect the three types of radiation alpha beta and gamma radiation alpha 6
13. ale on electronic meter this is the range 0 10 mR hr Moving to switch position 3 adjust pot V1 to give full scale on electronic meter this is the range 0 100 mR hr GM Tube GMT 01 LND712 GMT 02 GMT 06 0 1 mR hr 6 6 5 0 5 0 10 mR hr 2 5 1 6 0 25 0 100 mR hr 0 5 0 25 0 0 The procedure is the same for the GMT 02 however in position 3 full scale is 0 50 mR hr see figure 27 The procedure is the same for the GMT 06 however this tube has not been tested extensively enough to guage the mR hr So the mR hr for this tube 15 not known Once you have your Geiger Counter calibrated you may want to consider placing the circuit inside a case see figure 28 Figure 28 In order to secure the components properly inside a case the switches must be removed from the PC board and replaced with toggle switches wired to the PCB with about 6 inches of wire These switches can then be mounted to the front case Mounting all the components inside the case with front controls see figure 29 In this configuration I used the case horizontally rather than vertically as in the lead photograph You have the option of mounting the components any way you desire 1X 10X 100X Meter Range Amm Parts List 1 PCB Printed Circuit Board 4 0 01uF IKV C5 C6 C7 C8 1 O 1uF Cl 2 IOuF 16V C3 C4 1 1000uF 16V C2 6 1NA007 D2 D3 D4 D5 D6 3 200V Zener D8 D9 See text 1 5 1V Zener D7 1 LED D11
14. ed its time to attach the GM tube The Geiger Muller tubes have two leads For the LND 712 the lead connected to the metal sides of the tube 15 the ground This is soldered to the GM terminal on the PC board see figure 11 left circuit The center terminal of the GM tube has a removable solder lead Remove the lead solder 1 5 of wire to and Reattach the lead to the center 13 terminal of the tube Take the opposite end of the wire and solder to the GM terminal on the PC board Figure 11 The 712 Geiger Mueller tube s front mica window is delicate and should be protected by a screen open screen will protect the tube and at the same time allow the detection of alpha particles to pass through the front mica window The large and small glass GM tube in center position in figure 11 requires an anode resistor R5 of 3 3 mega ohms and a cathode resistor R4 of 470K ohms The regulated voltage required for these tubes is 400 volts DC You need to adjust the zener diodes in the regulator section to provide this voltage by shorting the jumper J1 The small GM tube the right hand circuit in figure 11 may be mounted to the PC board and strapped down using a few pieces of scrap wire After securing with a wire a small amount of glue or epoxy can be dabbed on the wire tube assembly for added support Each end of the GM tube has a wire soldered to its end and the wire soldered into one of the side holes In my tests the la
15. evel 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 1s 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 The digital Geiger counters I use 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 Exposure Source Dose conventional Dose SI Flight from LA to NY 1 5 mrem 015
16. f the GM tube through a current limiting 10 mega ohm resistor R5 The 10 mega ohm resistor limits the current through the GM tube and helps quench the avalanched ionization when a radioactive particle 1s detected The cathode of the tube is connected to a 1 meg potentiometer and a 100K resistor Each time a particle is detected a voltage pulse is generated across this resistance The pulse is fed from the wiper of the potentiometer to the inverting input to a 339 comparator The comparator cleans up the pulse and down streams it to the three other comparators The output of the second comparator feeds to the base of a 2N3904 transistor The transistor powers an LED and speaker so that each time a particle is detected the LED blinks and the speaker clicks The other comparator outputs are available for use by the user via Screw terminals on the edge of the board Alternative Audio Output To create a more pronounced click you can use the alternative audio output section The pulse signal from the comparator is a trigger to the 555 Timer The timer is set up in monostable mode that stretches out the pulse received on its trigger The output pulse from the timer flashes the LED and outputs an audible click to the speaker via pin 3 Construction You may hardwire this circuit to a breadboard or use the available PCB board Although you do not need the PCB the PCB will may construction easier see figure 5 D ij D ea o
17. for the meter section is shown in figure 24 ges me Ja 5V vas a gs gs gs g l g Figure 24 Q4 i a x sd I built this meter on a bread board and attached it to one of the Geiger Counter Circuits Or you can purchase the Analog Meter kit from Images SI Inc see figure 25 Power for the meter 15 taken from the 5V on the main GCK 01 board plus a ground The input to the analog meter 15 one of the digital outputs on the GCK 01 main board 20 Figure 25 Calibration of Electronic Analog Meter We can use a simple procedure to get a ball park calibration for the electronic analog meter The difficulty in calibrating the meter has much to do with the variables in play The tube s response can vary 20 The strength of the radioactive source can also vary in addition to variance in our electronic components All these factor affect accuracy With this being said we can proceed to get that ball park approximation for our meter This calibration procedure uses a 10 uCi CS 137 source see parts list The source is held at specific distances from the GM tube for each range When calibrating a range the pots are adjusted to give to give full meter For calibrating the GMT 01 tube LND712 see figure 26 ZA With the three position switch in position 1 see meter schematic adjust pot V3 for full scale this is 0 1 mR hr Moving to switch position 2 adjust pot V2 to give full sc
18. he halogen gas quickly quenches the ionization and the GM tube returns to its high resistance state ready to detect more radioactivity Dead Time For the short amount of time the GM tube is detecting one particle if another radioactive particle enters the tube it will not be detected This is called dead time The maximum dead time for the LND 712 GM tube is 90 microseconds or 00009 seconds There is a mathematical formula for adjusting a Geiger counter read out to compensate for the GM tube s dead time Different GM tubes have different dead times 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 Typically GM tube is calibrated using either a cesium 137 or colbalt 60 radiation source The chart is shown in figure 3 1s a typical response curve for a generic GM tube Each GM tube will have its own response curve to radiation For many of the GM tubes available on Ebay the response curve is not available Count rate vs Dose rate Cs 137 100000 O 11141 E 10000 1000 RETIRER ERG a IB EE ee eee ee ___ _ eee ee eee ee EP ee 10 LIT PL __ __ LI 7 Depp pp ag E Counts s H WE 100 CERE THE LTD EET LET LL CODE ELLE 1 L I1 j a pa Eie L L I1 j Eee L E 8 L I1 j L 1 j
19. lent radiation level It may also be set to count pulses per minute CPM and output an equivalent radiation value Secondly it is a true random number generator It uses the random time interval between radioactive particle detections to generate true random numbers The RNG may be set to a range of random number generated from 1 to 2 1 to 4 1 to 8 1 to 16 1 to 32 1 to 64 1 to 128 by selection switch setting It also outputs the CPS data serially which can be read by a PC for graphing and data logging To connect the Ground Figure 21 a DMAD to the Zo 7 Geiger counter we ay Le wire a 3 5 MM GEET socket to the digital Pin I output See figure 3 5 mm socket a output connects to the red wire to the socket and the ground to the NE ground The DMAD is sold with a 3 5MM male to male cable One end of the cable plugs into the digital input of the DMAD and the other end plugs into the socket we just wired to the digital output Figure 20 Radiation Network Software 5 GeigerGraph File User Setup View Network Help 20 HEME OS Counts Per Minute Time 7 Alert Level in Current 22 Day HrMn Se Set 100 Update Fi 22 Last 15 Average 17 Beginning 04 17 2011 02 50 02 PM Show on Graph igure Minimum 4 Ending 04 18 2011 08 52 00 AM Enable Alert Pop Up Maximum 53 Elapsed Time
20. n the pc board and bend them into place BEFORE soldering see figure 8 Mount and solder capacitors Cl O IuF C2 1000u F 16V C3 and IOu F 16V C5 C6 C7 and C8 0 0luF IKV Mount and solder mini step up transformer Mount and solder the 14 pin IC socket U4 11 Figure Finishing Board Construction Mount and solder U2 and Q2 Making sure their profile matches the silk screen outline of these parts before soldering Next mount and solder the bridge rectifier U3 Align the positive terminal of the bridge rectifier with the pad on the pc board Mount and solder the P2 external power supply connector Mount and solder S1 toggle switch Mount and solder on off slide switch for the speaker Next mount and solder the piezoelectric speaker The long lead on the speaker is positive and should be inserted into the pad on the pc board Mount and solder the 1 meg ohm potentiometer in the R6 position on the PC board Next solder the battery clip to the PC board The red wire is soldered to the P1 Bat pad The black wire is soldered to P3 Bat pad Finish the board by mounting and soldering the two pin header in the J1 position Your board should appear as in figure 9 12 C 5 Oc Tie Q 3 Output Figure 9 Insert the LM339 into the 14 pin socket see figure 10 Align notch on IC as shown in the figure 10 Figure 10 Attaching GM Tube s With the board complet
21. oc Image pm m w pm Figure 5 When using the board its merely a matter of mounting and soldering the components in their proper position All the parts are outlined on the top silk screen see figure 5 Begin by mounting and soldering all the resistors see figure 6 O 2 Output o g Figure 2 33 ohm color code orange orange black gold R3 and R7 1 meg ohm color code brown black green gold R4 470 K ohm color code yellow purple yellow gold R5 10 meg ohm color code brown black blue gold R8 R11 and R14 1OK ohm color code brown black orange gold R12 150 ohms color code brown green brown gold R13 100 K ohm color code brown black yellow gold These resistor values will change depending upon the specific GM tube used Default values are for the LND712 GM Tube Customizing circuit for GM Tube The two resistors R4 and R5 need to be matched to your GM tube also R5 is the anode resistor The anode resistor prevents too much current from passing through the tube when the tube detects a radioactive particle This resistor can vary between 2 2 mega ohms and 10 mega ohms for different GM tubes You need to read the specifications on your particular tube The Cathode resistor is R4 and may vary between 47 K ohm to 1 mega ohms for different GM tubes The voltage pulse across this resistor is fed to the comparator Zener Diodes
22. r counter to click In my corner of the world I have a background radiation that triggers the counter on average 16 Counts Per Minute CPM Adjust R6 until you hear approximately 16 counts per minute While the average CPM in my area is 16 the actual counts vary between a min count of 6 CPM and a maximum of 28 CMP The clicking can get annoying when performing some nuclear experiments so an on off speaker switch is available to turn off the speaker ACCESSORIES In this section I will look at the accessories one use with this Geiger Counter Data Loggers Digital Output This Geiger Counter has two digital outputs that outputs a 3 5V pulse with each detection of a radioactive particle I have tested the Lascar DataQ EL USB 5 Data Logger see figure 12 Figure 12 For anyone interested in data loggers you need to look for in a data logger that counts events Setting up this data logger is simple Install the program and USB driver on your PC Install the battery provided in the EL USB 5 Plug the data logger into a free USB port Run the installed program On the first screen see figure 13 hit the green button to set up USB Data logger 15 Set up and start the USB Data Logger Stop the USB Data Logger and download data View previously saved data The next screen figure 14 select Count events option Figure 14 FI Mame the USB Data Logger to give it a unique identity Logger Name Max 15 Char
23. rger of the glass GM tube is more sensitive to gamma radiation than the smaller glass gm tube due to its greater detection volume and area Radioactive Sources Uranium ore is available from a number of sources including e bay See suppliers list 14 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 4 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 U S Federal government to be license free and safe The cesium 137 is a good gamma ray source The cesium 137 has a half life of 30 years Adjusting sensitivity of Geiger counter Check Out You will need to adjust the sensitivity of the Geiger counter This is accomplished using potentiometer R6 Step one turn on the Geiger counter Step two make sure the speaker switch is turned on Step three if you have a radiation source bring it very close to the GM tube Step four adjust R6 until you hear clicking and see the LED blink Each radioactive particle detected will cause the Geiger counter to click and flash the LED Depending upon the sensitivity of your GM tube each click represents the detection of one of the radioactive rays alpha beat or gamma If you do not have a radioactive source background radiation from natural sources on earth and cosmic rays will cause the Geige
24. ube is first evacuated then filled with Neon Argon plus a Halogen gas Geiger Muller Tube lonizing 500 VDC Radiation Metal 10 Meg Tube Wall Anode Mica Window Cathode Signal Output Particle path 470K Ground Figure 2 Our GM tube is put into an initial state ready to detect a radioactive particle by applying 500 volt potential to the anode center electrode through a ten mega ohm current limiting resistor A 470K ohm resistor 1s connected to the metal wall cathode of the tube and to ground The top of the 470K resistor 1s where we see our pulse signal whenever a radioactive particle is detected In its initial state the GM tube has a very high resistance However when a radioactive particle passes through the GM tube it ionizes the gas molecules in its path and creates a momentary conductive path in the gas 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 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 creating a momentary avalanche of ionized gas molecules And these ionized molecules create a small conduction path allowing momentary pulse of electric current to pass through the tube allowing us to detect the particle This momentary pulse of current appears as a small voltage pulse across the 470 K ohm resistor T
25. und radiation level for your area The highest and lowest CPM count will establish your minimum and maximum CPM These numbers will establish a baseline so that you will be able to determine if the background radiation has changed or to detect trace amounts of radioactive materials If you look at the data I obtained from the Data Logger discussed later in the Excel spread sheet my average CPM reading based on 298 samples was 16 CPM The Minimum CPM was 6 and the Maximum CPM 28 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 recording the CPM output The longer the run obtaining CPM data the more accurate the results Compare the radiation output of your sample under test to your establish background radiation Images does not make any warranties express or implied about the radiation information provided here for your use All information provided should be considered experimental Safety and health issues and concerns involving radioactive contamination should be addressed confirmed and verified with local and national government organizations or recognized experts in this field Geiger Counter Schematic The circuit is shown in figure 4 The HV section of the circuit is built around a single transistorized TIP3055 ringing choke converter that has been around for years This particular derivative of the circuit was designed by Sam Evans to minimi
26. ze current draw The important element in this circuit 15 the transformer In this configuration the primary winding of the transformer and the feedback winding of the transformer are arranged so that the circuit begins a sustaining oscillation when power is applied If you checked the output of the oscillator you would find the waveform s duty cycle is symmetrical The primary oscillation amplitude is around 6Vat I4 1 kHz This gets amplified with the large step up ratio of the transformer and we obtain about 325V p p across the secondary The current consumption is about 5ma A simple voltage multiplier 1s used to boost up this voltage in steps to give a final DC of about 600V DC The high voltage output from this stage 1s regulated by zener diodes Here the user can decide which zener diodes regulators to use to vary the regulated DC output There are three zener diode positions on the pc board D8 D9 and D10 If one uses 200V zeners in each position the regulated output is 600 volts Using 100 volt zeners in each position the regulated output 1s 300 volts Using 2 200V zeners and 1 100 volt zener provides 500 VDC regulated output 330 483u82 1035 0 1 22125 _ Q om O s 23 19 eT LLLI Ie P Jamog HIGNT Mh Zh 001 005 em i 024 494 AS 210 B 024 613 Mb s umb y OT Ja aw 6 027 6 _ AS ueose SEENT hOGENZ FI 20 Yoon 5 po HOT aPNS x 031 A
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