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 Newbie Calibration Question
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James C

Germany
3 Posts

Posted - 02/14/2017 :  13:00:47  Show Profile  Reply with Quote
I just got a GMC-300E Plus and am trying to understand how it (and Geiger counters in general) work. I am a complete newbie but want to use the device during a visit to Chernoby in April. I am trying to understand how the CPM relates to the "dose" measurements such as micro sieverts per hour (excuse me if I am using the wrong terminology). For example:

Am I correct that the calibration values have no effect on the counts, simply on the corresponding micro Sieverts values?

Similarly, am I correct that the data logger only stores CPM. If I need to convert these into micro Sieverts per hour I would just find the average CPM for an hour and multiply it by whatever factor was stored in the device calibration settings? Which one though- slot 1, 2 or 3?

I took my device to a nearby official measuring station here in Germany and my device was reading 0.12 micro Sieverts per hour compared to the 0.09 micro Sieverts per hour that the official device was reporting. Probably not a massive difference (and better to read higher than lower??) but, if I wanted to calibrate this difference out, would I use the calibration slot 1, 2 or 3?

Does anyone know how long the battery lasts in a new device? I am currently testing ma machine in power saver mode. It has been running for three days and still shows full power.

Thank you for your patience with these basic questions :-)

James
Reply #1

Distelzombie

Germany
141 Posts

Posted - 02/14/2017 :  15:32:42  Show Profile  Reply with Quote
Hi James :)
quote:
Am I correct that the calibration values have no effect on the counts, simply on the corresponding micro Sieverts values?

Yes
quote:
Similarly, am I correct that the data logger only stores CPM. If I need to convert these into micro Sieverts per hour I would just find the average CPM for an hour and multiply it by whatever factor was stored in the device calibration settings? Which one though- slot 1, 2 or 3?

Yes it stores only the cpm and no, the calibration settings are just variables used for the calculation. The conversion rate of CPM to ySv/h (You should ignore röntgen) is cpm*0.005, factory standard. On the Internet the conversion rate is usually given in this format, which is stupid: 318 CPM/uSv/hr or this format, which is old and stupid: 44-49 cps/uR/sec (These values are for another Tube, not yours.)

Take a look at this thread from me. It shows quite good how it works. However, the Bug that is of question there has been resolved in the newest firmware - 4.20
https://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=4204

GMC-300E+ V4.20 with sbt-11 alpha tube

Edited by - Distelzombie on 02/14/2017 15:34:53
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Reply #2

James C

Germany
3 Posts

Posted - 02/14/2017 :  23:00:48  Show Profile  Reply with Quote
Many thanks Distelzomie. Very helpful!
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Reply #3

James C

Germany
3 Posts

Posted - 02/26/2017 :  14:00:36  Show Profile  Reply with Quote
I have now had the opportunity to do a few tests with my GMC-300 Plus. I think I understand how it works now. Check out my blog post at: h**p://www.colorgrinder.com/?p=273
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