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Eminem2Pac1984
Italy
4 Posts |
 Posted - 11/12/2021 : 11:02:33
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Hello dudes I'm new to the forum and I'm from Italy.
I don't know but probably I have a problem with the Geiger GMC-500+ when I switch the tubes.
I tested it into normal enviroments and i have 0.25 uSv and less than 50 CPM reads with the tube 1(more sensitive) while if i manual switch to the tube 2 i have a steady 0 CPM and 0 uSv and sometimes(rarely) it shows 1 CPM and 0.47 uSv in the same natural enviroment of the previous test with the more sensitive tube 1, do you think the tube 2 is broken? or it is too much "fat"(well capacity) to catch low emitting natural sources like the tube 1 does? Please help me cause I will return it if it is not a normal behaviour! |
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| Reply #1
Damien68
France
780 Posts |
Posted - 11/12/2021 : 11:26:44
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you can be reassured it is perfectly normal.
tube 2 is used to measure the rate of radiation when it becomes too strong for tube 1. that is why it is there and that is also why it is much much less sensitive.
your tube 1 vs tube 2 detections are quite consistent, it is only for very high levels with tube 1 in saturation that tube 2 can be useful. |
Mastery is acquired by studying, with it everything becomes simple |
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| Reply #2
Eminem2Pac1984
Italy
4 Posts |
Posted - 11/12/2021 : 11:42:33
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| Oh thank you thousands fr the reply! But I would like to understand why it measures wrong uSv compared to the "small" tube 1. For the test I go into the choosing tube menu and I alternate tube 1 and tube 2 in different tests. Thank you again for the support! |
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| Reply #3
Damien68
France
780 Posts |
Posted - 11/12/2021 : 12:44:29
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the creation of a radioactive radiation is purely random, and therefore a radiation detection is random.
tube 1 is bigger and has a larger effective physical detection volume than tube 2. therefore it intercepts more particles on average.
statistically speaking, when we have a random phenomenon, the precision of the calculation of the mean depends directly on the quantity of observation. in the case of weak radiation (~ 0.2-0.3 uSv / h) the detections made by tube 2 are very rare so in fact we have very few observations and therefore we cannot calculate an average in a suitable way.
in the case of high radiation on the other hand at this moment the CPS level of the tube 2 will then rise sharply and at this moment it will be able to provide information allowing a precise calculation of the average of the radiation.
the two tubes complement each other.
PS: it's because after around 300-1000 uS/h tube 1 may saturate and become less precise, at this level and over tube 2 will be better. |
Mastery is acquired by studying, with it everything becomes simple |
Edited by - Damien68 on 11/13/2021 01:59:27 |
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| Reply #4
Eminem2Pac1984
Italy
4 Posts |
Posted - 11/12/2021 : 13:18:31
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| Thank you again for the explained behaviour so basically it is working properly. Unfortunately i don't have any kind of gamma emitter so I cannot test the second tube :( |
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| Reply #5
Damien68
France
780 Posts |
Posted - 11/13/2021 : 02:02:27
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I don't have a source either, I only have a box of diet salt. it's safe  |
Mastery is acquired by studying, with it everything becomes simple |
Edited by - Damien68 on 11/13/2021 02:06:01 |
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| Reply #6
Eminem2Pac1984
Italy
4 Posts |
Posted - 11/14/2021 : 07:59:47
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| hahaha you are the top! thank you again dude! |
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| Reply #7
ullix
Germany
1171 Posts |
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Topic |
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GMC-500+ second tube problem?
