☢ Geiger Counter Basics ☢

Important fact: Radiation comes in many different levels of energy. Roentgens and Seiverts are two measurements of the energy deposited into anything exposed to radiation. 1 Serivert is equal to one joule of energy per kilogram of matter. One microseivert (uSv) of radiation means that 1,000,000th of a joule was deposited in a kilogram of matter.

Measure vs. Detected (Very Important)

Consider this math problem to explain:

An element deposits 10 units of energy for every ray it emits.
If you are hit by 2 rays, you are exposed to 20 units of energy (2x10).
If you are hit by 500 rays, you are exposed to 5,000 units of energy (500x10).

Now, suppose you calibrate a Geiger counter to measure this. Every ray is measured by the Geiger counter and the counter knows that measurement = rays x 10 units of energy. This is an example of a measurement. In the real world, we use Roentgens, Seiverts, or Grays to measure this.

What if you exposed the Geiger counter to a new element which deposits 20 units of energy per ray? The Geiger Counter would be hit by 5 rays, but it would only read 50 (5x10) when in reality it was exposed to 100, (5x20). The geiger counter still detected each ray, but failed to measure it correctly. In the real world, when ever a Geiger counter makes a tick sound, it has detected a ray or particle of radiation. These detections are still valid.

In this case, the Geiger counter could be recalibrated for the new element or you could merely understand that you were hit by 5 rays and ignore their energy. If you knew that anything under 100 rays per minute was safe, regardless of the energy, than you can use the Geiger counter without needing to understand the energy levels.

Your Inspector detects radiation and measures radiation for Cesium 137. This can be confusing. Your Geiger counter was originally calibrated using a sample of radioactive Cesium. This means that your instrument was placed near a sample of cesium 137 which had a well known radioactivity. The Geiger counter was adjusted until it read what it should.

Checking Your House and Food

When you get your Geiger counter, turn it on and set it to perform a timed count (in the manual). Place the Geiger counter in a safe place and run it for several hours. You will see the counter increment for each event detected (each tick adds one). The Geiger Counter will finish with a series of beeps. Take the number of events detected and divide that by the minutes timed to receive an average.

Example:
You run a two hour count (120 minutes) and find 2880 events. Divide 2880 into 120 minutes to get an average: 2880/120 = 12 counts per minute (CPM).

Take averages in several places in your house to get a good idea what the average for your house is. Consider these things when taking base-line counts:

1. The sun affects your count. This is fine, but remember this when testing.
2. The longer the count, the more accurate. 2-8 hours is good.
3. Airflow and movement of people can affect the results. A place without people is good.

Once you have a good set of readings for the house, find a good quite place to test food, etc. Test that place for a long time (12-24 hours). When testing food, you will place the food in the same place and test it for many hours. You will compare the food to the base line and see how far it deviates.

Example:
Baseline (8 hours) 14 CPM
Food (4 hours) 15 CPM - Most likely little to no contamination.

Baseline (8 hours) 14 CPM
Food (4 hours) 18 CPM - Perhaps some contamination.

Remember, when checking food, some foods are naturally radioactive. This is safe and not dangerous. Any foods high in potassium might read higher. Bananas, potatoes, tomatoes, etc. Also, Brazil Nuts contain small amounts of radium. These are all safe.

The big worry is surface contamination. Radioactive material in food is often passed through the body with little harm. A well washed food is often made safe.

Tips and Extra's

My normal ranges are 7 CPM -- 28 CPM (14 normally).
Anything less than 100 CPM is generally quite safe.

For my Geiger Counter, 100 CPM = 1 Micro Seivert of Exposre Per Hour (1 uSv/hr)

CPM = Counters Per Minute
uSv/hr = Micro Seiverts Per hour
mSv/hr = Mili Siverts Per hour
mR = miliroentgens per hour
mrem = milirems per hour

For my Geiger Counter, the conversion from uSv/hr to CPM is:
uSv/hr = CPM / 100 (For my Geiger Counter)
25 CPM = 25/100 = 0.25 uSv/hr

Roentgen = REM

These two are the same for most applications. They are actually different, but they are interchangeable for most instances.
Example: 23mR = 23mrem

1 Seivert / 1000 = 1 mSv
1 mSv / 1000 = 1 uSv
1 uSv / 1000 = 1 nSv

Websites:
My website:
http://anti-proton.com
GeigerCounters.com
http://www.geigercounters.com/AboutGgr.htm
USA Enviromental Protection Agency -- determine your annual exposure
http://www.epa.gov/radiation/understand/calculate.html

Category:

Education

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[FatimaSole]

thank you so much, Tom!! yours are the best videos about this subject online!! I couldn't have been able to use my Geiger properly if it weren't for you!! I do agree with the other comments, you should be a Professor, your efforts and educational content are great, and you make me think too!!! Best wishes!!

[antiprotons]

@FatimaSole Thanks. When i get my, one day, new Inspector EXP, I will remake this video a longer and much better quality series.

[GoddardsJournal]

Thanks Tom your efforts and educational content, and for putting up with me. :)

You should be a professor!

[antiprotons]

@GoddardsJournal No problem. Proper science leads to good results.

[antiprotons]

Please watch 17:20 and on to see my Uranium Mineral sample and Uranium Plate. Both are VERY low level and contain only tiny amounts of Uranium. The rock is almost a rounding error for Uranium (it might be thorium).

[antiprotons]

@PainterofYou My vaseline glass and uranium mineral sample are, perhaps, the weakest you will ever find. Most uranium samples produce thousands of counts per minute. Cesium decays at around 0.5 MeV most ofnthe time and uranium produces 4.2 MeV alphas. This means that a reading of 0.2 uSv of my plate really equals (0.2x1x8.4) 1.68 uSv most of the time and 0.7 uSv every so often (Cs uses two energy states).

[antiprotons]

NOTE: I need a new camera. Sorry for the sound.

When I get a new camera (The day I get my new, better, GM, I will buy a new camera) I will redo this video into several longer, and more detailed, parts.

Secondly, the sound part refers to the concept that radiation means energy which radiates. I explain that this is diffirent that Ionizing radiation.