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Alchemy2
Canada
89 Posts |
 Posted - 09/27/2014 : 21:53:29
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I just finished my retrofit of my second GM unit, and it works great!
I mounted the tube off the battery slot, and moved the battery to where the tube was. I used a short piece of RG-174/U cable to connect the tube direct, no additional resistors needed. I also had to dremmel out the slot where the old tube sat to allow my battery to fit properly inside the unit.
After some fiddling, we got it done! It looks pretty neat after mounting a small piece of Lund screen to protect the tube from damage!
The unit picks up now, bremsstrahlung from a small tritium keychain lite I had. Nice! Background is very low, still in the 18-30 CPM range.
WAY more sensitive than the stock M4011 tube, and I kept the old one as a spare for my first unit. I am using 270 CPM/uSv/h as my initial sensitivity. (SBT-11A claims 44-49 cps/mR/h). So I took the mean. I will check it later on with my calibration samples.
Nice...
More to come. |
The more I learn, the more I realize I do not know! |
Edited by - Alchemy2 on 09/27/2014 21:54:57
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| Reply #1
ZLM
1261 Posts |
Posted - 09/28/2014 : 19:29:51
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| Good. Pictures please. |
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| Reply #2
Alchemy2
Canada
89 Posts |
Posted - 09/29/2014 : 21:42:00
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Okay, second try!
Pix:
Image Insert:
125.16 KB
Basically, I mounted the SBT-11A tube by the battery cover and moved the battery to where the previous tube (M4011) was. I used RG-174/U coax for the tube connections to the board clips. No additional resistors required. Tube runs nice and quiet and is more sensitive and also responds to both alpha and low E X/gamma (<18keV Bremsstralung (X rays) from the low E betas off a tritium tube). I get around 80 CPM with the screen in place, vs 110 without it. I epoxied the tube to the back case, and same with the screen to protect the tube. The battery cover after trimming with a Dremmel was adhered using CA glue. The main board where the stock/old M4011 tube sat was carefully cut back by ~8mm to give more room for the battery size. It is tight getting together, but is good.
Another pic:
Image Insert:
79.02 KB
All in all, this was a great retrofit for unit #2 - more sensitive and better all around suitability to general samples. I get >4500 CPM on a Thorium sample which only reads around 900CPM with my unit#1, with stock 4011 tube.
For that fellow wanting low/soft X-ray responses, this would be a good choice! I get <18.6 keV! Tube should read soft X-rays to at least around 5 KeV now...
Alchemy2 |
The more I learn, the more I realize I do not know! |
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| Reply #3
ZLM
1261 Posts |
Posted - 09/29/2014 : 22:25:39
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| It looks really cool. |
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| Reply #4
Alchemy2
Canada
89 Posts |
Posted - 09/30/2014 : 20:24:50
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THanks!
Yes, and it still remains handheld :)
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The more I learn, the more I realize I do not know! |
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| Reply #5
CuaC
Germany
3 Posts |
Posted - 04/23/2016 : 04:46:03
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quote:
Originally posted by Alchemy2
I just finished my retrofit of my second GM unit, and it works great!
I mounted the tube off the battery slot, and moved the battery to where the tube was. I used a short piece of RG-174/U cable to connect the tube direct, no additional resistors needed. I also had to dremmel out the slot where the old tube sat to allow my battery to fit properly inside the unit.
After some fiddling, we got it done! It looks pretty neat after mounting a small piece of Lund screen to protect the tube from damage!
The unit picks up now, bremsstrahlung from a small tritium keychain lite I had. Nice! Background is very low, still in the 18-30 CPM range.
WAY more sensitive than the stock M4011 tube, and I kept the old one as a spare for my first unit. I am using 270 CPM/uSv/h as my initial sensitivity. (SBT-11A claims 44-49 cps/mR/h). So I took the mean. I will check it later on with my calibration samples.
Nice...
More to come.
I have just installed an SBT 11a in my 320plus, did you finally test the tube against your calibration sources? which values did you get? |
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| Reply #6
Distelzombie
Germany
202 Posts |
Posted - 04/25/2016 : 13:20:24
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Yeah. I would like to know them too.
Let's hope he's looking into this forum from time to time. :) |
GMC-300E+ V4.20 with sbt-11a alpha tube
My statements are "stuff-a-hobbyist-says" and not in any way professional. |
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| Reply #7
Radioman1985
11 Posts |
Posted - 04/10/2021 : 08:52:32
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| I just ordered a SBT-11A tube and can't wait to try installing it with my GMC-320! The one issue is that I have a limited understanding and experience in building electronic devices and working with components. From what I understand in this thread, the SBT-11 can be simply connected without using resistors or any extra components, correct? When I came across this discussion https://radmon.org/index.php/forum/geiger-muller-tubes/691-sbt-11a-photographs it seems like everyone is installing resistors. I'm just curious if anyone can explain the difference between using a resistor on each pin separately vs. simply connecting the pins together to one wire. Is there going to be a huge difference? Any input is appreciated! |
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| Reply #8
Damien68
France
780 Posts |
Posted - 04/10/2021 : 11:22:57
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Hi Radioman,
the anode resistance is already on the PCB of the GMC-320, so no need to add another one.
you just have to connect the anodes of the SBT11 to the anode clip, and the cathode to the cathode clip.
the anode resistance serves to limit the current flowing through the tube.
you can connect the 3 anodes pins together to one wire and the 2 cathodes pins together to another one wire.
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Mastery is acquired by studying, with it everything becomes simple |
Edited by - Damien68 on 04/10/2021 12:49:04 |
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| Reply #9
Radioman1985
11 Posts |
Posted - 04/11/2021 : 03:03:53
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| Thank you Damien for that information! That greatly simplifies things for me. I plan on making an external wired probe with this instead of attaching it to the case of my GMC-320, are there any suggestions for the type of wire to use (gauge, special insulation considerations, etc)? I also purchased a socket made for the SBT11 which should make connections much easier since I have basically zero soldering skills and with less risk of pin breakage |
Edited by - Radioman1985 on 04/11/2021 03:08:25 |
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| Reply #10
Damien68
France
780 Posts |
Posted - 04/11/2021 : 03:47:04
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it is better to have cable not too long,
it is better if they are thin because the current is very low and its capacitance / inductance will be less.
you can use a coaxial cable by connecting the cathode to the center of the cable because it is on the cathode that the current is measured.
you can also use a normal cable (non-coaxial) but you must not touch the cable even through its sheath because it risks inducing EM interference by capacitive coupling.
in any case it should work. |
Mastery is acquired by studying, with it everything becomes simple |
Edited by - Damien68 on 04/11/2021 03:53:54 |
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| Reply #11
Searinox
Romania
51 Posts |
Posted - 04/11/2021 : 12:21:36
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| While the idea is nice, remember the 320 does not support voltage or dead time adjustment. While the voltage can be adjusted from hardware, dead time is a software calculation and cannot be changed unless the firmware supports it. The device's counting also rolls over after 65535 counts in a minute, which is easy to reach and surpass with stronger sources on a tube as sensitive as the SBT-11. It will work, but the device is limiting your tube's true potential. |
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| Reply #12
Damien68
France
780 Posts |
Posted - 04/11/2021 : 15:22:38
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SBT11 is same voltage (400v) so no require adjustments.
for dead time you can ignore the difference ther is only low action under 1.000 CPS or 60.000CPM
if max count is 65535 .... be careful not to exceed them :)) |
Mastery is acquired by studying, with it everything becomes simple |
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| Reply #13
Radioman1985
11 Posts |
Posted - 04/12/2021 : 11:00:46
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| Thanks for the feedback. Honestly I didn’t expect to become this interested in the world of radioactivity and Geiger counters. My background and interests were mainly in chemistry but I always wanted a Geiger counter... now I’m fascinated and interested in experimenting further and would love a more sophisticated counter but unfortunately money is the limiting factor as usual. At least I can experiment with this tube and use it with other counters down the road. My needs are fairly basic at the moment (measuring uranium glass, fiestaware, a sample of uranium acetate etc) and so I’m not too worried about dead time etc. For now my goal is to get this tube connected and working with the counter and then take things from there! |
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| Reply #14
ullix
Germany
1171 Posts |
Posted - 04/12/2021 : 23:53:02
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Just to be sure there is no misconception sinking in:
The deadtime is a property of the Geiger tube. It is determined by its construction and cannot be changed later.
A Geiger counter device may make the effective deadtime worse by poor construction of its electronics, but cannot make it better.
When "setting deadtime" was discussed here it referred to the possibility of some GM counters to set up a a count rate correction for high count rates.
I am not very fond of those kind of mal-corrections of previously good data. And on top its implementation in the GM counters is not appropriate.
If your counter does NOT offer such correction, consider yourself lucky. If it does, better switch it off!
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| Reply #15
Searinox
Romania
51 Posts |
Posted - 04/13/2021 : 01:14:19
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| @ullix Yes this is understood. But the ability of setting voltage and dead time in a device become important if you intend to switch tubes. If you cannot set the voltage from software for your new tube, you may yet be able to use a simple hardware modification to increase or decrease it. However, if you are unable to configure dead time in the software, then you will not be able to change it to match that of your tube. A device like GMC-600 can do these things and so it is very flexible with swapping tubes. But a 320 cannot. Both the M4011 and popular SBT-20 do not come close to saturation at 65535 CPM so dead time indeed is negligable. I did however, note that these tubes are limited by the device in this way because they can hit 1 mSv/h and in fact I know at least the SBM-20 works correctly well over its maximum spec, into as high as 4 mSv/h, and so the device's 65535 CPM cap which equivalates to about ~450 uSv/h will limit the tube. |
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| Reply #16
Damien68
France
780 Posts |
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| Reply #17
Radioman1985
11 Posts |
Posted - 05/17/2021 : 11:01:25
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The SBT-11A finally arrived after more than a month! Canada Post is having issues with COVID infections in the mail centres and my package remained there for a long time. Looking forward to installing this cool gadget… it also looks like the seller installs protective grid over the window which was not mentioned in the advertisement, bonus!!
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| Reply #18
FBSMatt
Ireland
32 Posts |
Posted - 08/15/2021 : 05:16:59
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| slightly irrelevant question. Is the GMC-600 no longer a thing? I don't see it for sale anywhere. For a while it was the cheapest way to obtain one of these tubes for me. Was honestly quite close to buying one recently. |
What Signature? |
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| Reply #19
Damien68
France
780 Posts |
Posted - 08/16/2021 : 00:47:45
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right, it looks like the GMC-600 doesn't exist anymore.
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Mastery is acquired by studying, with it everything becomes simple |
Edited by - Damien68 on 08/16/2021 01:36:32 |
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| Reply #20
EmfDev
2250 Posts |
Posted - 08/16/2021 : 09:54:34
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| We dont have anymore GMC-600 in stock. |
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| Reply #21
jlam
5 Posts |
Posted - 08/26/2021 : 11:17:03
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This is so cool! If you ever crack it open, could you take a few pics on how you did it?
Thanks :) |
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| Reply #22
Damien68
France
780 Posts |
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| Reply #23
jlam
5 Posts |
Posted - 08/27/2021 : 03:46:54
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| Thank-you Damien, I completely missed those :| |
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Topic |
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Second GMC-320 plus with SBT-11A
