Coincidentally, I sell geiger counters. So the following may not be unbiase= d :) You can detect radon by proxy by picking up the decay of it's daughter prod= ucts. It's non trivial to convert geiger counter readings into radon level= s (pCi/liter) and while my detectors can be used to detect radon, they don'= t measure actual radon levels, and I don't sell them as products to do such= .. If your goal is to get accurate radon levels, you should buy a product de= signed to do that.=20 But you can observe changes in radon levels fairly easily by observing the = change in the geiger counter output (counts per minute) as it is relatively= linear. From experimentation, it varies with the weather; high and low pre= ssure systems can affect the flow of radon gas from the ground into your ho= use (typically the basement). You can even use a fan and piece of filter c= loth to trap the radon daughter products in front of the geiger tube, essen= tially amplifying the signal. (I sell such a contraption)=20 A "pancake" style geiger tube has a large area mica window, and is substant= ially more sensitive to the alpha and beta rays from the radon products vs = a small diameter end window tube, it's a function of the tube window surfac= e area. Of course you can increase your averaging time period to reduce sta= tistical noise, the rule that doubling the averaging period reduces the noi= se by the square root of two applies.=20 "Typical" background radiation levels vary with the sensitivity of the geig= er counter which is a function of the tube type and size. In engineering un= its, 10-20 uR/hr is a good ballpark figure. Higher if you live at high alti= tudes or in areas with high background radiation levels . This is 10-20 CPM= with a small end window tube and maybe 45-90 CPM with a large pancake tube= .. Mostly what you are detecting here is cosmic rays (hence the altitude var= iation), the pancake detector is not significantly more sensitive for them.= =20 Chris Smolinski Black Cat Systems Westminster, MD USA http://www.blackcatsystems.com > On Sep 30, 2018, at 12:24 PM, Wouter van Ooijen wrote: >=20 >=20 >> I would like to learn: what it would take to design my own radon gas met= er? >> (For fun, not commercially) Any advice or links to resources (formulas, >> charts) would be greatly appreciated. >>=20 >>=20 >=20 > The setup you describe doesn't measure radon perse, but alpha particles.= =20 > As far as harm to you that doesn't matter much. >=20 > The detector you describe is a Geiger-Muller tube. The main challenge=20 > (apart from filling the tube with a specific gass at a low pressure) for= =20 > detecting alpha particles is that nearly everything (including a sheet=20 > of paper, to give you an idea) will block alpha particles. A very thin=20 > sheet of mica seems to be the preferred window material. Summary: don't=20 > try to build your own alpha-detecting GM tube, buy one. >=20 > The rest of the circuit isn't that special and examples can be found on=20 > the web. >=20 > You probably won't gain much in 'instanteneous readout': the amount of=20 > (detected) alpha particles is very low, so averaging over some period is= =20 > required to get a measurement with some accuracy. >=20 > --=20 > Wouter "Objects? No Thanks!" van Ooijen >=20 > --=20 > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .