Conversion factors.

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7 years 9 months ago #121 by ThibmoRozier
Here we go. ^_^

Most of this topic I could recover.
Got it.
A small chart to compare tubes.
[img]https://dl.dropboxusercontent.com/u/3572198/Chart%20-%20GM%20all%20tubes.png[/img]

To save the calculations for you.. :P 
0.0039
Hello guys, thought this would be handy to post newly calculated conversion rates. :)
M4011:
Test info taken from here: http://tskagawa.com/?page_id=2061

Known:
Conversion rate for SBM-20 --> 0.0057

Calculations:
uranium glass bead 238U :
SBM-20 --> 290cpm * 0.0057 = 1.653µSv/h
M4011 --> 1.653µSv/h / 245cpm = 0.0067469387755102

uranium ore 238U :
SBM-20 --> 471cpm * 0.0057 = 2.6847µSv/h
M4011 --> 2.6847µSv/h / 436cpm =  0.0061575688073394

smoke detector pellet 241Am :
SBM-20 --> 896cpm  * 0.0057 = 5.1072µSv/h
M4011 --> 5.1072µSv/h / 790cpm = 0.0064648101265823

lantern mantle 232Th full size:
SBM-20 --> 5253cpm * 0.0057 = 29.9421µSv/h
M4011 --> 29.9421µSv/h / 4386cpm = 0.0068267441860465

Averaging:
0.0067469387755102 + 0.0061575688073394 + 0.0064648101265823 + 0.0068267441860465 = 0.0261960618954784

0.0261960618954784 / 4 = 0.0065490154738696

0.0065490154738696 <-- rounding to 4 digits behind the dot --> 0.0066 <-- Theoretical conversion rate for the M4011 after applying maths. :)

Hope this helped out. :)
The following user(s) said Thank You: filewalker, Electrodemente

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7 years 6 months ago - 7 years 6 months ago #661 by RH Electronics
Replied by RH Electronics on topic Conversion factors.
Great Thimo! :)
I would add that using alpha/beta filter is definitely required when extracting conversion factors with this method. So I'm sure we cannot use the chart because we don't know if alpha/beta filter was used, I suppose these reading where taken without filter. If you make a practical test to extract the factor use at least thin aluminum foil between the tube and radiation sample to cut alpha and beta.

I attach electrical information for the tubes.
Attachments:
Last edit: 7 years 6 months ago by RH Electronics.
The following user(s) said Thank You: Frank, Electrodemente

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7 years 6 months ago #666 by Frank
Replied by Frank on topic Conversion factors.
This is great for the beginners, what about the M4011 tube, seems to be a common tube out here, are they not good enough to make it on this list? I don't know much about the tubes in general so would or is this model tube on the lower end of the list and not a preferred tube over the ones listed as these are perhaps better performers?

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7 years 6 months ago #667 by RH Electronics
Replied by RH Electronics on topic Conversion factors.
Frank, I do not speak about tube X is better than tube Y.
I speak about conversion factor number that applicable ONLY for GAMMA radiation. The diagram from the link dl.dropboxusercontent.com/u/3572198/Char...GM%20all%20tubes.png is present cpm values from different sources that contains alpha/beta/gamma radiation pollution. The measurements where taken without alpha/beta filters to allow only gamma detection. So my conclusion that this diagram is not applicable to extract conversion factor numbers. You have to apply filter before you extract the factor. Usually aluminum foil is enough to filter alpha and beta.

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7 years 6 months ago #669 by Frank
Replied by Frank on topic Conversion factors.
Agree with you and wasn't really stating x against y, was just wondering why I see charts with these factors and didn't know why the tube I have here is not listed, that's all. Thank you

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7 years 6 months ago #670 by RH Electronics
Replied by RH Electronics on topic Conversion factors.
Found this about tubes from China. Somebody have datasheet for M4011?
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