| T O P I C R E V I E W |
| fotongamma |
Posted - 11/11/2022 : 11:03:58
Hi. Im new here.
I wanted to change M4011 tube to SBM-20. Can someone did that? What calibration factor i must use? Did i must change tube voltage?
How reliable measures will bo on new tube? |
| 3 L A T E S T R E P L I E S (Newest First) |
| ullix |
Posted - 11/12/2022 : 23:31:26
The GMC counters with their M4011 tubes are not calibrated for anything. It is simply the average of the 2 numbers reported for the SBM-20 tube.
It is a kinda, sorta, in the ballpark type of value.
The different factors for different radiators are to be expected, as they have different gamma spectra, and the sensitivity is mathematically the result of folding the spectra with the spectral response of a Geiger tube.
An example for a response curve is also in the Calibration chapter of the GeigerLog manual (Fig 65 in the 1,4,1 manual), and spectra are there as well.
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| fotongamma |
Posted - 11/12/2022 : 10:37:10
Thank you. I see M4011 has different Cf for gamma than SBM-20. And SBM-20 has different Cf for Ra-226 and Co-60. It is normal thing, but i dont know for what isotope GMC 500+ was calibrated for. I think it was may be Cs-137 like most meters.
No problem with soldering job, i made some of my DIY geiger counters in the past, but i want the measures to be reliable. |
| ullix |
Posted - 11/12/2022 : 01:14:10
No need to change anything. The only challenge is to mechanically fit the SBM20 into the holder for the M4011. Some old experiments with the two tubes are here: http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=4571
You can use any "calibration factor" you want. In fact, the GQ calibration factor is taken as the average of the SBM-20 factors. For deeper insight see chapter "Calibration" in the GeigerLog manual. https://sourceforge.net/projects/geigerlog/files/
For Geiger starters I suggest my "Potty Training" from here: https://sourceforge.net/projects/geigerlog/files/Articles/
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