uSv/hr Conversion Factor

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8 years 2 months ago #1939 by Simomax
Hello!

I know this has been briefly discussed here, and also on other sites but I would like some clarification about the conversion factor for the SBM-20.

From what I have read it should be approximatly 0.0057 according to most sources, but my NetIO GC-10 came with a conversion factor of 0.0067 (CPM / 150). I have changed my GC-10 to a factor ot 0.0057 just like Radmon software and other documentation. I am wondering why my GC-10 came factory set at 0.0067 and not 0.0057. I do understand the conversion is a very loose figure that shouldn't be relied on with a non-professional counter, but still I would like to have my counters as accurate as possible. So, 0.0057 or 0.0067, or somewhere in between?

Cheers,

Simon.

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8 years 2 months ago - 8 years 2 months ago #1942 by mw0uzo
Replied by mw0uzo on topic uSv/hr Conversion Factor
I simply chose 0.0057 because it seemed to be the most used value across the web. Of course it could be wrong, there will some small variation from tube to tube but nothing significant. If some tests indicate a more accurate value, let's use that!
Last edit: 8 years 2 months ago by mw0uzo.

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8 years 2 months ago #1945 by Simomax
Replied by Simomax on topic uSv/hr Conversion Factor
I was starting to get the feeling that the figure was an educated guess by someone, and maybe that is the case. I have done a little more research about the conversion factor and looking at a couple of sites (below) and it seems there are different conversion factors for different radionuclides (as well as different tubes, but concentrating on the SBM-20 here). On one page it states the following:
60Co - Cobalt-60 = 0.00664
226Ra - Radium-226 = 0.00504
137Cs - Cesium-137 = 0.00584

After briefly reading bits of those two sites it seems that the 0.0057 conversion factor is a about in the middle of the range 0.00504 - 0.00664, which is actually bang on 0.00584, not far from 0.0057.

It is a very confusing subject and I'm guessing one that would require some very expensive gear (and radioactive sources) to actually pin a proper number down to it. But then add in some fudge factor for not all tubes or counters being the same, slight variances with tube voltage and probably a whole load of other factors. I think the 0.0067 conversion factor my GC-10 came set with is that of 60Co, or it is just a number the creator decided to use.

I think I'll stick with 0.0057 for now unless I find some information that is more specific and go with the notion 'if it clicks like crazy, run!'

https://sapporohibaku.wordpress.com/2011/10/15/conversion-factor/
https://sites.google.com/site/diygeigercounter/gm-tubes-supported

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