GM Tube Conversion Factor Calculator
4 hours 45 minutes ago #7628
by Simomax
GM Tube Conversion Factor Calculator was created by Simomax
Hello, hello!
For a while I have been working out my own conversion factors for GM tubes based on the specification supplied in the datasheet, if available. It's not too difficult, but does often requires conversion between units - Sievert, Roentgen, Gray etc. I thought an online calculator would be really handy for other users, so I wrote one. First, full disclosure - I didn't write this, AI did. I vibe coded it. I gave the AI a complete specification of what I wanted and this is the end product. It works quite well.
https://www.blinkyslab.co.uk/gm-tube-conversion-factor-calculator/ or https://www.blinkyslab.co.uk/cfcalc/ for a standalone page with the calculator.
Important: This calculator is mathematically correct. It is valid only for the isotope specified in the datasheet, and the conversions between Sv, R and Gy are best case calculations, as Sievert is effective dose, Roentgen is exposure and Gray is absorbed dose so they can't really be interchanged directly.
To use the calculator you need to know the specified sensitivity. Some datasheets provide this, some don't. Some provide isotope specific sensitivities, some don't. I am going to use the Robotron 70 013 to describe how to use the calculator. The Robotron tube specifies the sensitivity to be (Cs-137): 10 cps/µGy/hr according to the datasheet. This means 10 counts per second equals 1 Gray per hour for Cs-137. So in the calculator we would enter 10 in the Counts field, as this is CPS, we select 'second' in the Count period field. For the Dose / exposure we leave this at 1 unless specified (this spec doesn't specify this so we always assume it to be just 1 mR). Then the unit - the datasheet specifies µGy (micro-Gray), and finally the period. In this case hour. The image below should help understand what goes where. Notice there is no Dose / exposure bit. Some specifications may state something like 2000 CPS/10 mR/h. In that case, the 10 from the 10 mR would be entered into the Dose / exposure field. But if nothing is present then we assume just 1.
Generally you will be calculating the conversion factor for µSv/h, which is highlighted in bold in the result table.
The calculator also has a list of presets. These are specifications from datasheets just written in a CSV that the calculator picks up. I have added a few of my tubes already. Use at your leisure. Please report any bugs or suggestions. Some kind of instructions are necessary and I'll sort them in time.
If you do have any datasheets with the actual tube sensitivity specs that I don't currently have then please give me a copy and I will gladly add them to the list of preset tubes. It doesn't matter what language they are in so long as they include the sensitivity spec. Either drop them in a reply here or by email - use the contact link at the bottom of my site. Or just send me the link if already online.
One thing I did notice was when calculating the conversion factor for a couple of known tubes was the number I calculated was way out from what I have found online. Almost like where the actual f**k did that number come from? Bear that in mind. Like I said, this is mathematically correct based on the datasheet specification, or the best specification found for the tube. I think the conversion factors for a couple of tubes may simply be guest guesses.
For a while I have been working out my own conversion factors for GM tubes based on the specification supplied in the datasheet, if available. It's not too difficult, but does often requires conversion between units - Sievert, Roentgen, Gray etc. I thought an online calculator would be really handy for other users, so I wrote one. First, full disclosure - I didn't write this, AI did. I vibe coded it. I gave the AI a complete specification of what I wanted and this is the end product. It works quite well.
https://www.blinkyslab.co.uk/gm-tube-conversion-factor-calculator/ or https://www.blinkyslab.co.uk/cfcalc/ for a standalone page with the calculator.
Important: This calculator is mathematically correct. It is valid only for the isotope specified in the datasheet, and the conversions between Sv, R and Gy are best case calculations, as Sievert is effective dose, Roentgen is exposure and Gray is absorbed dose so they can't really be interchanged directly.
To use the calculator you need to know the specified sensitivity. Some datasheets provide this, some don't. Some provide isotope specific sensitivities, some don't. I am going to use the Robotron 70 013 to describe how to use the calculator. The Robotron tube specifies the sensitivity to be (Cs-137): 10 cps/µGy/hr according to the datasheet. This means 10 counts per second equals 1 Gray per hour for Cs-137. So in the calculator we would enter 10 in the Counts field, as this is CPS, we select 'second' in the Count period field. For the Dose / exposure we leave this at 1 unless specified (this spec doesn't specify this so we always assume it to be just 1 mR). Then the unit - the datasheet specifies µGy (micro-Gray), and finally the period. In this case hour. The image below should help understand what goes where. Notice there is no Dose / exposure bit. Some specifications may state something like 2000 CPS/10 mR/h. In that case, the 10 from the 10 mR would be entered into the Dose / exposure field. But if nothing is present then we assume just 1.
Generally you will be calculating the conversion factor for µSv/h, which is highlighted in bold in the result table.
The calculator also has a list of presets. These are specifications from datasheets just written in a CSV that the calculator picks up. I have added a few of my tubes already. Use at your leisure. Please report any bugs or suggestions. Some kind of instructions are necessary and I'll sort them in time.
If you do have any datasheets with the actual tube sensitivity specs that I don't currently have then please give me a copy and I will gladly add them to the list of preset tubes. It doesn't matter what language they are in so long as they include the sensitivity spec. Either drop them in a reply here or by email - use the contact link at the bottom of my site. Or just send me the link if already online.
One thing I did notice was when calculating the conversion factor for a couple of known tubes was the number I calculated was way out from what I have found online. Almost like where the actual f**k did that number come from? Bear that in mind. Like I said, this is mathematically correct based on the datasheet specification, or the best specification found for the tube. I think the conversion factors for a couple of tubes may simply be guest guesses.
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