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and_kom
Ukraine
24 Posts |
 Posted - 10/27/2012 : 13:42:47
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Is it possible to connect SI8-B Russian Pancake tube to GMC-300?
Image Insert:
140.22 KB |
Young and radioactive |
Edited by - and_kom on 12/28/2012 04:02:14
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| Reply #1
ZLM
1261 Posts |
Posted - 10/31/2012 : 10:17:24
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| It should work. But you need to find a way to stick SI8B on back side of GMC-300. |
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| Reply #2
and_kom
Ukraine
24 Posts |
Posted - 11/03/2012 : 22:44:05
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I tried to connect but it showed very high reading of CPM which grew rapidly up to several tens of thousands...
Then I tried to connect it to another counter instead of SBM-20 and it seemed to work ok.
Seems GMC-300 circuit doesn't support such kind of device. |
Young and radioactive |
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| Reply #3
ZLM
1261 Posts |
Posted - 11/04/2012 : 19:34:45
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You need to adjust the tube voltage.
Check your tube vltage. |
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| Reply #4
and_kom
Ukraine
24 Posts |
Posted - 11/08/2012 : 10:53:22
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quote:
Originally posted by ZLM
You need to adjust the tube voltage.
Check your tube vltage.
I've tried to adjust voltage but it didn't help. CPMs were growing up to 600-700 and more in each case and it was not expected behavior. Also I have noticed that speaker emitted more continuous clicks with less volume. Also I've tried to add 5,1 MOm anode resistor but got the same behavior. |
Young and radioactive |
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| Reply #5
ZLM
1261 Posts |
Posted - 11/15/2012 : 11:24:39
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| confrim your tube is good. Otherwise some other adjustmnent needed. |
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| Reply #6
and_kom
Ukraine
24 Posts |
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| Reply #7
hdripper
Switzerland
3 Posts |
Posted - 03/26/2015 : 13:43:48
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I'm sorry to be digging out this old thread, however I'm having exactly the same behavior with this tube, also in a GMC-300.
The background counts are way too high and easily exceed 600 CPM and often end up in the thousands. I am using an additional 22 MOhm resistor directly in front of the anode. Oddly, adjusting the tube voltage with R25 does not seem to have any significant effect on CPM.
EDIT: I have "manually" counted the actual CPM by recording the clicks through microphone and lookin at the waveform -> The clicks CPM from the tube is actually OK at roughly 150 CPM, as to be expected!  So the problem would be related to how the signal is interpreted/counted by the mcu?
Is there anything I can do to the input circuitry to improve the impulse detection? |
Edited by - hdripper on 03/26/2015 18:33:21 |
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| Reply #8
Nudnik
40 Posts |
Posted - 03/26/2015 : 23:48:42
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Sounds like there is some noise on the wiring from the tube to the board. How long is the cable? Have you tried a shielded cable?
Maybe a shielded cable plus a lpf between cable and pcb would help.
Nudnik |
under construction |
Edited by - Nudnik on 03/26/2015 23:49:22 |
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| Reply #9
hdripper
Switzerland
3 Posts |
Posted - 03/27/2015 : 02:08:55
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At the moment it is just a test setup with regular wires, albeit fairly short (10 cm). The proper shielded cable should arrive next week. Definitely something to try out!
On the other hand, since the original poster had exactly the same problem, which did not appear on the open source “DIYGeigerCounter”. So assuming that he was using a similar connection method on both counters, I’m not entirely sure if this will be solved by shielded cable, next week I should know more.
I still wonder why the audible clicks are correct but the display CPM reading is not... It seems like the clicks and CPM reading are each triggered seperately from the GM signal?
Also I am waiting for some 1 Gigaohm resistors to arrive so I can make proper measurements with the oscilloscope 
EDIT: I searched some more through the forum and found this which looks very promising for now:
http://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=3766&SearchTerms=cpm,increase |
Edited by - hdripper on 03/27/2015 09:59:58 |
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| Reply #10
ZLM
1261 Posts |
Posted - 03/27/2015 : 15:22:10
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| I think there are some small noise signal along with the main pulses. The small noise can be picked up easily by the micro processor, but it is not easy by speaker and ear. |
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| Reply #11
Nudnik
40 Posts |
Posted - 03/28/2015 : 04:30:11
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| Would be interesting to hook up a DSO to see whats going on. |
under construction |
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Topic |
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SI8-B (СИ8-Б) Tube
