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February 25, 2011
about 4 years ago
For what it’s worth, here’s the conversion numbers I’m using based on reading the spec sheet for the tube and various and sundry internet resources. Remember, as others have pointed out, there are big differences between alpha, beta, and gamma, as well as far too many other factors to easily summarize. All this counter is good for is to estimate exposure…
* For the ND-712 tube used in the Sparkfun geiger counter, we know the following dry air dose rates for Co60 gamma response:
* 100 CPS = .000055 R/hr (Roentgen)
* 101 CPS = .00055 R/hr
* 103 CPS = .055 R/hr
* The next step ramps up sharply. Time to run…
* 104 CPS = 4 R/hr
* Using the following conventions, derived as best I can from various internet sources:
* - assuming dry air exposure
* - assuming gamma
* - using that assumption, Roentgen converts to the following absorbed dose equivalents:
* - 1 R = 0.877 rem
* - = 0.00877 Sievert
* - = 0.877 rad
* - Some simply round to 1 R = 1 rad = 1 rem. I’ve used the .877 factor… change as you see fit!
For those who don’t like 1’s and 0’s, there’s some examples of Arduino code here: http://forum.sparkfun.com/viewtopic.php?f=8&t=26559&hilit=geiger+code
In the 60 minute averaging mode, I’m seeing 12 - 18 CPM; usually 12.
Have fun, and post your hacks!
Can this be battery powered? If there’s no USB connection, can it be powered by 5V through either the programming socket or JP2? On the spec sheet (v19) I don’t see any obvious reasons why not, but I’d like some knowledgeable input before cooking a $150 toy…
That version still only emits 0’s and 1’s; I’ve never seen the “counts per second” triggered by a timer overflow.
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