SBT-10 Geiger Tube avalanche issues

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5 years 4 months ago #3102 by stdorn01
so recently I've been having issues with one of my Geiger kits I thought the kit was messing up but after viewing my SBT - 10 tube in the dark I realized it was an avalanche issue on one or two of the sections of the sensor tube. I am currently using just one dropping resistor for the whole tube would it make any difference with the Avalanche problem if I were to use a dropping resistor for each section of the tube. Does anyone have any input on this or ideas on resolving my Avalanche problem? Does this possibly mean I just have a bad tube?
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5 years 4 months ago - 8 months 1 week ago #3103 by Simomax
Hi Steve,

I would try using a seperate resistor for each section of the tube. I have mine with a 10Mohm on each section (see pic below) and appears to work OK, though I haven't had it running for long and just some simple tests. When I got mine I scoured the web looking for info but it seems there is very little. One recurring theme was that the voltage and resistor(s) did play a very big part on getting correct counts from the tube.

From this site: sites.google.com/site/diygeigercounter/gm-tubes-supported

SBT10-A - alpha tube A good tube for measuring food? This report from Pedro (thanks for keeping us in the loop):
"Finally the replacement for the faulty SBT10-A tube arrived and after connecting it to the arduino the counter shows a 160/190 CPM with all the segments connected to a 10Mohm resistor. The anode voltage seems to be critical for this tube as it creates avalanches if anode voltage is over 370v. Care must be taken in the voltage calibration as most voltmeters will show erroneous reading due to intrinsic impedance, so in my case the adjustment was made to 330v (digital readout) but the real voltage without voltmeter load was 370v. In my case this tube detects 2400 CPM for a lantern mantle at 10cm from the mica window without alpha blocked and 690 CPM with alpha blocked."
[7/22/16] A customer reports that 10MΩ is too low for this tube. He had expected results with as high as 30MΩ. He used that resistance on every anode of the tube. He also said that the sensitivity to the HV setting described above is explained by too low of anode resistance.
For the conversion ratio, I calculated using Method 2 below, and got a ratio of 1641 CPM / uSv. Seems high, but is a sensitive tube.


You could try changing the resistor(s) for a higher value as per the text above. What I have found, accidentally, was that if I connect another 10Mohm resistor in series with the tubes my CPM increases a little for each of my check sources.

Plaese let me know if you have any joy or find any more info as I would be very interested in any more info on this tube.

Simon.
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Last edit: 8 months 1 week ago by Simomax.
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5 years 4 months ago #3106 by stdorn01
Simon,

just like you I have found very little information online regarding this tube at least compared to information available on all of the other Geiger tubes that I have purchased. I had to order some higher-value resistors but in the meantime I added a 1 Meg resistor to each section of the tube in series with the 4.7 Meg in the kit and so far I have not had an avalanche problem again.
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5 years 4 months ago #3109 by Simomax
Cool, good stuff. From the little info I have found, others' are suggesting a minimum of 10Mohm resistor(s) upto even 30Mohm.
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5 years 4 months ago #3130 by Electrodemente
:evil:

Another guy on the "SBT´s-10 TUBEs Club".

Thanks for your impressions and comments. Are very hepful.

My SBT-10A is on the way to me...so, soon I hope I could show to the community some pics of how I mounting it and impressions compared with my actual M4011 and SBM-20 tubes.

Best regards.

ElectroDemente.
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5 years 4 months ago #3133 by Simomax
That's great Electrodemente. It will be interesting to see what you do with it. There are a couple 3D printable housings for the SBT-10 on thingiverse.com if you have a 3D printer: www.thingiverse.com/search?q=sbt-10&sa=

I would also be interested in knowing the condition of yours when it arrives. Mainly to compare with the black spots that stdorn01 and I have on our tubes: radmon.org/index.php/kunena/radmon-org-n...4-sbt-10-geiger-tube
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