Do-it-yourself Geiger Counters, Radioation Measurement and Infos on Radioctivity
An Independent Citizen Sience Project
A short intro (pdf-file)
Intro to the basics (pdf-file)
The Tino Shield
The Tino Shield is a plug-on PCB stacked on an Arduino microcontroller board. With the Arduino it forms a real measurement instrument calibrated by Teviso, Switzerland (external link to www.teviso.com), the manufacturer of the radiation sensor module.
Arduino programs for the Tino shield can be found on the download page.
Description of the shield
Yes, it really works: You can measure the specific radon activity in a given air volume with a geiger counter.
This graph shows the measurement result of radon exhalation in a chamber which was filled with a granite stone from Menzenschwand (Black Forest area) at time zero. After ten days the stone was removed carefully and the chamber was closed again continuing the measurement. Finally, after 18 days the chamber was opened completely and the detector was kept on running. The pile-up of radon activity with the half-life constant of 3.8 days is clearly visible followed by disintegration with the same time constant. Well, it was not a normal geiger counter that was used for this measurement. It was the "Radon-Geigerle", a modified version of the "Stuttgarter Geigerle" that was made sensitive to alpha radiation. However, the cost and effort was surprisingly small, it is only required to exchange the photodiodes. During further investigation it turned out that even regular granite building material exhales quite a lot of radon depending on the source of origin and the content of uranium. More in the follwing documents.Analysis of the radon exhalation from granites with the "Stuttgarter Geigerle"
Rolf-Dieter Klein developped an Android app that uses the camera sensor of a mobile phone as a detector for radioactivity and thus converts the mobile phone into a geiger counter. For some devices this works quite well since the author provides support for the settings of the key parameters. For other phones the app does not work that well. Since the camera sensor is pretty similar to a PIN-diode detector a comparable strategy for finding the comparator settings can be used for the Stuttgarter Geigerle. Therefore it is possible to learn a lot from this app with respect to the correct comparator threshold. Here you'll find a description telling you how to do the adjustment of the parameter settings for the Android phone app on your own after having understood the principle of operation.External link to the website of the app www.hotray-info.de
Recently I had to consult the dentist. After pushing the trigger of his x-ray gun for the third time I asked him whether he would know the dose rate of his machine. Embarrassed he answerered: "I can't tell you exactly but during a training for radiation protection I learned that this is not more than during trip with an air plane for vacation. I was too reluctant to ask how much such an air plane trip would add to my yearly absorbed dose.
Such type of answer is often used to quiet the people who try to ask for a dose rate. However I wanted to once know this for sure, so I carried my geiger counter (Gammascout) with me during a trip with the plane and had the instrument logging the data. The result was that during the 4 1/2 hour trip from my home town to the island Teneriffe at a height of 10900m I absorbed a cumulative dose of 13uSv. Right after reaching the cruising height in Germany the dose rate was highest with 3uSv/h. The average along the flight was 2.5uSv/h. This matches well with what can be found in literature and in the Internet. During the flight to Teneriffe the dose rate decreased steadily towards the South and on the return flight it was opposite. This obviously is the result of the magnetic field effect of the planet earth on the radiation particles. The effect is the stronger the closer a flight position is to the magnetic poles. Therefore the routes across the poles cause a higher accumulated dose.
Now we can compare: a vacation trip to Teneriffe is equivalent to spending 3.6 days on the granite pavement of Stuttgarts main shopping road the "Königstrasse" (see below).
And with respect to medical radiography, a thorax x-ray photograph causes a dose of about 0.2-20mSv and a mammography screening causes 15-65mSv of equivalent tissue dose (University of Bonn).
This means the dentist did not pay enough attention during the x-ray training course.
The city of Stuttgart provided an ideal test track to its afficionados that is now even measured and analyzed officially. So if someone needs to calibrate its geiger counter he only needs to walk along the main shopping road. This road is paved with a special granite from Flossenbürg (Oberpfälzer Wald in Bavaria). The pavement extends from the Rotebühlplatz to the central station Hauptbahnhof). This granite ranges among the Top 10 of the most uranium containing granites in Germany. This increases the local gamma dose rate to 0.3uSv/h in 1m above the pavement. This is a factor of 3 compared to the neighboring road the Kronprinzstrasse, which is asphalted. The finding caused some emotions when it became public.