? temperature effects on GM tube.

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6 months 3 weeks ago #6173 by FSM19
Yesterday and today there has been a significant drop in counts in the late afternoon, and a higher level round midday. Here in Portugal we are experiencing extreme heat and also forest fires. There are two fires burning locally, and temperatures have peaked at 39C both days. Could the temperature be affecting the count?  
 

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6 months 2 weeks ago #6175 by FSM19
Everything back to normal countwise, although temperatures are still high. I did move the gm-tube out of direct sunlight, and check all connections.

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6 months 2 weeks ago #6177 by jnissen
Based on some of the data I have looked at for remote sensors there does not appear to be a trends that would imply heat changes the counts appreciably. I have had my sensor in the heat, in a window sill, cold, etc... and it's still relatively stable on the trend charts.

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6 months 2 weeks ago #6180 by Radslug
I've not seen any data supporting that temperature within "normal" human ranges affects counts. The attached electronics on the other hand can very much be affected, some components more than others. Especially the high voltage section.

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6 months 2 days ago - 6 months 2 days ago #6188 by Bert490
There is good evidence of light affecting certain glass GM tubes, particularly the M4011 tube and J305 that are used for the popular GQ-Electronics detectors.  GQ has added blackout material to recent batches, but it remains unclear what the root cause is, due to the tube OEM being opaque in both name and materials (see  https://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=9862  and other posts at that site).  Even with the blackout covering, some tubes remain light-sensitive.
Last edit: 6 months 2 days ago by Bert490.
The following user(s) said Thank You: FSM19

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2 months 3 weeks ago - 2 months 3 weeks ago #6265 by bwalter
Temperature would definitely effect the impedance of the tube and the load resistance of the high voltage supply.
Whether this would effect counts is a good question.

From the manufactures specification sheet for the SBM-20:
Operating Temperature Range -50 - +70 Deg. C.
This would be the recommended temperature range to maintain the specifications as listed for the tube.

M4011 operating temperature:-40°C~55°C
J305    operating temperature: -40°C~55°C

As previously stated by Bert490, exposure to light is most likely the cause of excessive counts.
Last edit: 2 months 3 weeks ago by bwalter. Reason: added supporting data

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