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 GMC-300S Default Calibration?		  New Topic  Reply to Topic
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Max530

1 Posts
Posted - 08/06/2024 :  20:29:59  Show Profile  Reply with Quote
I am hoping someone can tell me the default calibration from factory for the GMC-300S. When I go to Calibrate 1, there is a CPM number, can anyone confirm what their's says in that spot?
Reply #1

Kaninbjerget

Denmark
18 Posts
Posted - 08/06/2024 :  22:01:12  Show Profile  Reply with Quote
You could just factory reset it then it'll default if you mixed something up.
But if you got a long tube (~107mm J305, the longest tube that fits PCB) it's 161.5 CPM pr. uS/h. Can both be multiplied by 10 if i remember correctly (haven't got it here).
If you have an approx 88 or 90mm tube, can be marked M4011, J321 or to make confusion complete also J305. Then it's 153.8 CPM / uS/h.
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Reply #2

Kaninbjerget

Denmark
18 Posts
Posted - 08/07/2024 :  08:37:50  Show Profile  Reply with Quote
Just verified. GMC-300S (mine with long tube) is set to 1615 CPM for 10 uS/h for first calibration point. The following are just multiplied accordingly.
GMC-800 with either M4011 or J321 is 1538 CPM for 10 uS/h for first calibration point. Again following are just multiplied accordingly.

Reason for edit: forum doesn't like the greek u
Edited by - Kaninbjerget on 08/07/2024 08:41:10
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Reply #3

Tony81269

USA
37 Posts
Posted - 08/17/2024 :  16:28:40  Show Profile  Reply with Quote
I haven't bought one of these GQ brand meters but I do have serious questions about calibration. I work in the Well Logging industry and I deal with the NRC on at least a yearly basis. Our survey meters have to be calibrated to certain standards in labs. There are specific requirements. For analog meters it is "Accurate to 20%, and must be calibrated on each scale twice, at approximately 1/3 and 2/3 of full scale deflection" an on digital models it is "must be calibrated at one point per decade over the range that will be used". Must be done every 6 months. So, I look at the description on Amazon and it says they will give you a certificate upon request and then they say something about having a third party to do it for extra money. I find this confusing. Is it really calibrated to NRC standards when you buy it? Or do you have to pay to have that done?The lack of information leads me to think these aren't really professional instruments. Anyone ever try to have one of these meters calibrated at a licensed place?
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