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 2.GQ Geiger Muller Counter
 sudden jumps in CPM

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mgcdenmark Posted - 05/26/2016 : 11:12:55
Hi there.
I just bought the GMC-300E Plus Geiger.
It reads CPM aorund 12-20 - which i guess is normal. but 3 times during the afternoon it jumps up to appr. 200 and the alarm sounds.
Do you know why this happens ?- It falls down to normal level after 2 minuttes or so.
I have not calibrated the detector - should i do that ?
6   L A T E S T    R E P L I E S    (Newest First)
Distelzombie Posted - 04/01/2018 : 15:44:03
"Driving by"? I know they can throw tens or hundreds of millisieverts when pumped with technetium, but "driving" seems a bit fast for this device. Have you observed this in detail? Very interesting, nonetheless. :)
shawn85206 Posted - 03/28/2018 : 23:39:22
I get these weird high readings on my 320 Plus (200cpm) and wondered about it...then realized that what I am likely seeing is nuclear medicine patients from M D Anderson Cancer Center driving past my house, full if whatever isotope they were injected with, or with seeds implanted!

I also wondered if I'd pick up sources on the way to the hospital, I'd think no, that they would travel in shielded containers like industrial radiography sources are...but maybe not?
wd9dui Posted - 09/17/2017 : 12:33:09
Well just received my new GMC-320 Plus, my life has gone back to normal, no more shy high readings!
wd9dui Posted - 09/13/2017 : 09:59:03
I have a GMC-300E FW 3.10, since 2012, it has just stated to go way off on readings, up to 1500 CPM at times and will go high through out the day off and on, this all started a week ago. After doing some reading it maybe the tube maybe needing replacement. I have made a decision just to replace the unit with an new 320 plus. Technology has change over the years and sometime the new stuff is better......
ZLM Posted - 05/26/2016 : 16:52:34
I think you may need to watch it for a longer period. If it happened again , then contact
Distelzombie Posted - 05/26/2016 : 14:09:57
Is someone carrying bright orange dishes around.

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