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 2.GQ Geiger Muller Counter
 GMC-320 Plus high counting

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T O P I C    R E V I E W
Erfanra Posted - 06/22/2017 : 07:34:25
I have a GMC-320 Plus Geiger counter and I have tested with radioactive sample and it shows about 4000-7000 cpm when it is connected to the charger or pc via usb cable and when i disconnect the cable then it shows 700cpm with same sample, what is the problem?
anybody have this problem?
And is it normal that it takes about 2 minutes until it counts down and reduces 5000CPM to normal background radiations ?

Er
1   L A T E S T    R E P L I E S    (Newest First)
ullix Posted - 06/25/2017 : 00:31:46
I got such significant discrepancies in count rates only with my light-sensitive tube. See the in-depth discussion here: http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=4540

Follow that post to verify that your tube is NOT light-sensitive!

CPM=7000 is not lethal but also not negligible ( see calculation here http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=4568) . Are you sure that your source could even give off such a high level of radiation? What kind is the source? Is it beta or gamma?

The tube itself adapts to a new radiation level within a millisecond or less, because that is how long a single pulse lasts. But in CPM mode the counter sums up all the events over the past minute, and hence it should adapt to a new rate level within exactly 1 minute. Compare with picture for a change from 550CPM to background. If it takes longer, then something else is going on.

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