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 GMC300E Nonsense Readings		  New Topic  Reply to Topic
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alannz

New Zealand
5 Posts
Posted - 10/06/2013 :  13:10:46  Show Profile  Reply with Quote
I have a new (as in a couple of weeks old) GMC300E which I am having a lot of problems with.

1) the readings are nonsense
2) if you turn the speaker on the reading goes up to 1000 to 2000 CPM

I did the following test with the only source I have, a uranium glass jug.
Each part of the test had a duration of five minutes.

Speaker Off

a) turned device off (for 5 mins)
b) background - reading about 20 cpm (OK)
c) near jug - reading about 40 cpm (OK)
d) removed jug - returned to 20 cpm (OK)

Speaker On

e) background - reading about 20 cpm (OK)
f) near jug - now about 200 cpm (NONSENSE)
g) removed jug - now 400 to 1000 cpm (NONSENSE)
h) turned off speaker - dropped to 300 cpm (NONSENSE)

(I have the graph for this but the forum s/w won't let me post it)

I then left the device running and USB logging for five days with the speaker
off. The reading started at around 20 cpm for some hours which
I believe to be the correct background reading.

The reading rose to the 200-300 mark peaking over 800. The average
on the graph (by eye) over five days is about 300 cpm.

Having been at 300 (up to 800) cpm for five days. If I turn the device off
for ten minutes and then on again the reading drops to the true
reading of 25 cpm.

This is clearly a faulty device. How can I get it replaced?

Thanks
Alan
Reply #1

alannz

New Zealand
5 Posts
Posted - 10/06/2013 :  13:26:46  Show Profile  Reply with Quote
Here are the graphs for my previous post:

The jug test. Time runs from right to left:

Image Insert:

15.35 KB

General "background" logging, Time runs from left to right.
The right half starting with the low correct values is the
uninterrupted speaker off log over 5 days. Note the general trend from
day-to-day is climbing.

Image Insert:

31.67 KB
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