Hello, I've had a GMC-300e for a while now and over the past few months I've kept it on out of curiosity and I always observe a cpm around 15-20 and the average sits around 15-20 as well. This AM I looked at it and saw an average of 230+, but the dynamic cpm display is still a steady 15-20. I saw an average CPM spike of 500 a few months ago with the same steady cpm of 15-20 on the display.
I chalked that 500 reading up to an overflow error or some bug since the unit had been on for so long, and I restarted it. This time, seeing this large reading, I decided to take a picture of it and then observe if it's decaying over time. This 225 reading from the picture below is now down to 221.2 a couple of hours later, so it has me wondering if there really was this giant gamma spike at some point and my average is now decaying, or can a bug be causing this? I'm thinking of plugging it into my PC and plotting CPM over time, but I don't have Windows and it would take a bit of effort. Is this a known bug? I can't see what would transiently put out a large gamma or beta spike like this just sitting here at home. Nobody has visited who has undergone a recent Technetium contrast exam. 
(edit: shrank image showing 225 reading down)
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GMC-300e Plus Average CPM Spike
Posted - 06/10/2026 : 07:33:42
