Geiger Counters 101 -- The Basics, Part One

Geiger Counters 101 -- The Basics, Part One



The history of the Geiger-Mueller tube
Basic Geiger tube concepts
New Geiger counter? What do you do?
Taking a baseline/background reading
various tips and tricks.

There are no prerequisites other than you have an interest in radiation and Geiger counters.

Five things to remember:
(1) Always use CPM (Counts per minute) unless you are calibrated for the specific, known, element and radiation source you are detecting.
(2) There are four common ionizing radiation types: Alpha, Beta, Gamma, and X-Ray.
(3) A Geiger Counter which is turned off detects NOTHING. Keep your unit on and stay informed.
(4) You cannot check too slowly. Do not rush your examinations of objects.
(5) Identify and monitor your baselines. A reading without a baseline is of little use.

[WildMidwest]

Thirteen years later and this video is as amazing as the day you released it. Bravo! (subscribed)

[Anti-proton]

I have not run my CRM100 in a few months, but in my lab it was 14 CPM and my Inspector was 38 CPM. Both have been the same for about 2 years.

That background reading is only good for my office. It varies all over the place as you walk around.

My Ludlum model 12 gets about 2000 CPM in the same room :)

[JudiBechard]

Very helpful Tom.  Thank you for taking the time to explain things so thoroughly.

[dankit]

Awesome brother Thanks for taking the time to make such informative videos.

[greengrowlocks]

If you put any or all of your counters (including scinitilators) directly in front of a x-ray beam, would it be damaging in any way to the detector or scinitilator? Is there like limit that will cause damage?

[Shadowofiris]

Very nice video thank you. I hope in the future you might do a video on how to calibrate a geiger counter.

Most geiger counters will give you a reading of microSV per hour and so on. Based on what you say it's really the count per minute that matter. How do the makers of these geiger counters calculate microSV then? Is there a presumption about the source of the radiation built in to the calculation? For example is it presumed to be CS-137 or something?

Thanks again!

[doutchesinse]

hello dutchsinse. good to hear from you.

[Anti-proton]

The actual number of gamma rays, x-rays, charged particles, etc, passing through us, per second, is in the millions. Our detectors only see a little of it. What we look for is not the magnitude of the reading (a common misconception), but the change in the reading. If your Gamma Scout goes from 14 CPM to 100 CPM, it more of a jump than my Ludlum going from 2000 to 4000 CPM.

I should do a video explaining actual interaction levels lol

[Anti-proton]

This video is full 1080P!

NOTE: Please view in 1080P (button in bottom right hand corner of video screen).

[zzzdogutube]

Tom, Thanks for the info. Ron from NY

[Anti-proton]

@shadowofiris My next video will include the math of Geiger counters and explain how to caluclate the units correctly.

[nicholashamilton]

I own a Gmc - 320 nuclear geiger counter, i never knew what the small hole on top or side of of the Geiger counter are for ? Is it used to plug in your Geiger tube.for a more accurate result.

[Anti-proton]

@shadowofiris To understand this, we need to know what a Sievert is. 1 Seivert = 1 Gray x several factors to account for biological effects. For simplicity, let's look at gamma and whole body exposure. In this case, an absorbed dose of 5 grays would equal an equivalent dose of 5 seiverts... 1 to 1. 1 Gray = 1 joule of energy deposited into 1 kilogram of mater. Thus, 1 sievert = (x joules / y kg) x some conversion factors of equiv. dose. (continued)

[leefiles]

thanks I'll check it out. I'll let you know if I grow another arm. could come in handy.

[Anti-proton]

@shadowofiris cont...

So, a gray and a seivert had at least two or more degrees of freedom:

seivert: energy / mass

(note: these conversion factors I refer to take a gray and account for the differneces in radiation and the body parts it affects. The result is a seivert)


Now, if you know the energy of the target and the Tube has a fixed mass... you can calulate seiverts / time easily:

Sv/t = (Counts x Energy / GM_mass) / t

(cont...)

[Anti-proton]

The Americium 241 in smoke detectors emits alpha and gamma radiation. The real danger is if the Am241 gets loose. If you remove that little button from inside, the Am241 can easily escape as a fine powdery substance. Inhaling even a little of this would be VERY bad and cleanup is VERY costly.

[WorldView]

What is the life of the tube inside such a geiger counter? I read that the tube gas can (gradually or due to damage?) escape and render the geiger inoperable or inaccurate? Is this true and to what extend? Also, what is the value (in terms of accuracy and life) of counters that do not use tubes but e.g. Semiconductor silicon (Si) (photodiode (PD)) like the Japanese S.T. Corporation's Air Counter S?

[Anti-proton]

You often end up with u instead of mu due to the lack of support for some systems. Over time, I end up just using such substitution. Interestingly, I named my cat, Mu Schrödinger. In computer science, we often use substitution letters as computer has historically not appreciated Greek. Of course, Mu is actually in extended ASCII as character 230 lol

[Anti-proton]

Yes, the Gamma Scout and CRM100 have the exact same Geiger tube: the LND712.

[leefiles]

I'll find some on amazon or ebay. thanks.

...I always wondered about my new forth nose.