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horseflesh
3 Posts |
 Posted - 05/14/2012 : 13:58:01
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For a baseline, background radiation in both the Seattle area and Los Angeles is about 20-25 CPM.
I found an old watch with a radium dial. I believe the watch was made in the early to mid 60s. It reads 1100 CPM. (The radium markings produce no visible light.)
My family has a very old hand-made ceramic bowl with an orange glaze. It read 1600 CPM. Jackpot!
A small stack of Depression glass plates read about 60 CPM. It was easy to verify which plates were actually vintage and made with uranium, and which were normal green glass. Of course you can do that with a UV light too, but where's the fun in that?
At about 37,000 feet in a jet, background radiation was about 975 CPM, as seen on the screen in real-time. But when I looked at the minute-by-minute log data for the flight, the scores recorded at each minute were much lower. For example:
5/8/12 6:43 Every Minute 170
5/8/12 6:44 Every Minute 1
5/8/12 6:45 Every Minute 3
5/8/12 6:46 Every Minute 145
5/8/12 6:47 Every Minute 62
5/8/12 6:48 Every Minute 170
This is what I am really confused about--the mismatch between CPM on the screen and the value recorded to the log. Can anyone explain?
Last note:
I also put the unit through the baggage X-ray machine. According to the log, for about 20 seconds it picked up 150-200 CPM.
I assume that the baggage X-ray uses higher power pulses for less than a second, because it doesn't seem like your exposure inside the plane should be about the same as what a bag gets.
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Edited by - horseflesh on 05/14/2012 14:00:13
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| Reply #1
ZLM
1261 Posts |
Posted - 05/15/2012 : 13:20:19
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The real-time is the true reading
When doing data log, the every second data should be selected. otherwise you may not get correct data is your machine only turned on for a very short period.
You listed data log list seems not correct for minute data, it looks like a seconds data.
You may need to download the data again and see if it consistant with previouse download.
You can post your data here so that I can check it for you. OR send your data file to support@gqelectronicsllc.com. |
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| Reply #2
phgphd
USA
12 Posts |
Posted - 05/17/2012 : 19:35:42
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ZLM -
The CPM readout updates every second. Does this mean that the GMC300 is calculating the CPM based on the last 60 samples of CPS? |
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| Reply #3
ZLM
1261 Posts |
Posted - 05/19/2012 : 18:10:54
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I means you need to turn on the data save feature and select Every Second data type. In this case, each second data will be saved into internal flash memory. And you can download it later.
Yes. The CPM is calculated based on the last 60 secodns CPS. It is a simple sum calculation. |
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Readings from my GMC-300--confused about logging
