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 Post subject: Geiger Counter - Error in ratio ?
PostPosted: Tue Apr 02, 2013 9:27 pm 

Joined: Tue Apr 02, 2013 8:02 pm
Posts: 2
Hi,

Here :
http://www.cooking-hacks.com/index.php/ ... o_servants

True or not ?

I found for Co60 :
- LDN-712 :
18cps for 1mR/h
1080cpm for 1mR/h
1080cpm for 10µSv/h
108cpm for 1µSv/h
Ratio = 1/108 = 0,009259259

- SBM-20 :
22cps for 1mR/h
1320cpm for 1mR/h
1320cpm for 10µSv/h
132cpm for 1µSv/h
Ratio = 1/132 = 0,007575758

- J305β Geiger Tube :
65cps for 1µR/s
3900cpm for 1µR/s
3900cpm for 3600µR/h
3900cpm for 36µSv/h
~108,334cpm for 1µSv/h
Ratio = 1/(3900/36) = 0,009230769

Thank you
Fred


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 Post subject: Re: Geiger Counter - Error in ratio ?
PostPosted: Wed Apr 03, 2013 8:47 am 

Joined: Mon Sep 28, 2009 12:06 pm
Posts: 11366
Hello Fred,

We can not help you with so little information.

Please try to explain your questions.

Regards.


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 Post subject: Re: Geiger Counter - Error in ratio ?
PostPosted: Wed Apr 03, 2013 5:18 pm 

Joined: Tue Apr 02, 2013 8:02 pm
Posts: 2
Hi,

I am not sure if there is an error in calculation of ratio in this page :
http://www.cooking-hacks.com/index.php/ ... o_servants
(in section : "From counts per minute to Sieverts")

For the formula
Quote:
cpm * conversion factor = μSv/h

You say
Quote:
LDN-712 tube is 0.01" and for the "SBM-20 is 0.0057

For cobalt 60 :
- I found LDN-712 tube = 0,009259259 =~ 0.01 (it's ok why not).
- I found SBM-20 tube = 0,007575758 <> 0.0057 (it's different).
But for Radium 226 :
- I found SBM-20 tube (29cps/mR/hr) = 0,005747126 =~ 0.0057 (very similar).

And now for J305β geiger tube.
I am don't understand where you found "8,77".
Quote:
1080/8.77 = 123.14 cpm/µSv/h


For J305β Geiger Tube with cobalt 60 sensibility :
In datasheet, cobalt 60 sensibility = 65cps/µR/s;

It means: 65cps for 1µR/s
-> (65cps*60)=3900cpm for 1µR/s
-> 3900cpm for (1µR*3600)=3600µR/(1s*3600)=h
-> 3900cpm for 3600µR/h
But 100µR=1µSv :
-> 3900cpm for 36µSv/h
So :
-> 3900cpm/36 for 1µSv/h
~108,334cpm for 1µSv/h
Ratio = 1/(3900/36) = 0,009230769

Best regards,
Fred


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