| Author |
 Topic  |
|
|
fotongamma
Poland
2 Posts |
 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? |
|
| Reply #1
ullix
Germany
1171 Posts |
|
| Reply #2
fotongamma
Poland
2 Posts |
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. |
 |
|
| Reply #3
ullix
Germany
1171 Posts |
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.
|
Edited by - ullix on 11/12/2022 23:32:06 |
|
|
| |
Topic |
|
GMC 500+ and SBM-20 tube
