Testing Geiger Counters 277
thesandbender writes "My girlfriend's family lives in Japan and is very interested in obtaining geiger counters for testing food and other materials. Geiger counters are now impossible to get in Japan and are on long back order from most providers in the U.S. which makes me suspicious of anything we can get our hands on. My question is, what's the best way to test/verify a geiger counter. I know I can point it at a smoke detector and it should go off but I'm not sure what I should see on the gauge. We'd even take it to any reasonable local facilities for testing (NYC area). Any input would be greatly appreciated!"
Don't get one. (Score:4, Insightful)
99% of the general population can't operate one. Measuring radiation is not like measuring signal strength of an electromagnetic field. People forget that it's radioactivate _matter_ emitting radioactivity, something akin as if you had tiny mobile towers all over the place. There is a large difference between a weak emitter stuck to your geiger counter and a powerful source a lot further away, but radioactivity-wise at a specific point they are indistinguishable. There is a large difference between different kinds of radioactivity aswell.
Geiger counters are useless for someone without at least a basic education in nuclear physics.
Re:Geiger Counter (Score:1, Insightful)
In case you didn't know what it was (like me):
You didn't know? Really?!
Call me cynical but for a moment there it looked like you were just karma whoring.
Re:Don't get one. (Score:5, Insightful)
Unless you are picking lettuce from the grounds of the Fukushima nuclear power plant that scenario isn't going to happen (and anyway you should ALWAYS wash produce, the pesticides etc that get used aren't exactly great for you either).
From what I have read the fallout is at such low levels that it is within the bounds of variation in background radiation (ie mostly the levels are below what you would get from living in a high altitude area like Denver, Colorado). Unless you are in the immediate vicinity of the leaking reactors you aren't going to get a dose that has immediate effects, and just ignoring the whole situation will cause less damage then regularly eating junk food.
People in general are fucking terrible at risk assessment, and that is before you use the word "radiation".
There are several different types of radiation detectors with varying degrees of accuracy, and the type you can scrounge around and get now are probably not worth the money even if you put in the time and effort to calibrate and understand it.
Re:Don't get one. (Score:4, Insightful)
Re:Vaseline glass. (Score:2, Insightful)
??? What kind of logic is that ???
The same logic that was used to get the 1mSv/year value to begin with.
Because of lack of studies IAEA pulled that value out of their asses.
4mSv or even 3.14159265mSv/year is just as valid as 1mSv/year.
In the end the guidlines are just there too keep stupid people from eating too much uranium.
Re:Regular salt - it contains potassium-40 (Score:5, Insightful)
one milligram of potassium-40 should give you 263 decays/second, and so on.
You have a good idea there but all these are rough estimates. The actual counts would depend on the distance from the source (in effect the solid angle), the instrument's sensitivity, the source's geometry and other stuff I may be forgetting.
I have done instrument calibration (as a student, not as a lab manager, so I am not an expert by far) on both Geiger-Müller counters and solid state detectors. Calibration was mandatory before the actual measurements took place. Even in laboratory conditions, with experts running around and helping out, point sources and 0.5mm accuracy on distances and the like, let's just say that they turned out to be not the easiest instruments to use, and people where ending up being off (but not way off) in their estimates for the actual activity of the radioactive sources.
Furthermore, there are different 'types' of 'radiation'- alpha, beta, gamma, neutrons. Depending on your counter/instrument, you could measure on or more of these; also there is math to be done afterwards; some instruments (like G/M) measure just 'counts' (the event when a particle 'hits' the detector), others can give more detail. And you need to do some math afterwards, unless the instrument itself does it for you.
My punchline; its use is not trivial, it needs some training (not impossible, though). In times of need such as these I would assume that the few instruments that find their way to Japan would be put to much much better use if they are delivered to experts.