Hi from Melbourne, Australia (too!)

G'day!

I'm from Melbourne (Box Hill South to be exact), and I recently purchased and assembled a GK-B5 Geiger Counter and the GKnet v2 kit with a view to eventually having it monitor background radiation as part of a weather station project. I'm intending to mount a 1963-made STS-6 tube outside in some plumbing/electrical pipe and run the signal inside to the Geiger kit. For the moment I'm just experimenting with this tube and a SBM-20 tube I bought at the same time (made in 1989 about the same time I was studying nuclear physics and doing experiments in the lab there ). I've only just compiled and uploaded the sketch to the GKnet with test data mode on to check the network module I bought will work correctly (it's a WizNet 5100 but with a header that's mostly the same as the one for the ENC28J60 module on this board) so the initial data that might come through (hopefully!) will be random test data only.

I've also purchased a ~1960 Nuclear Electronics Corp IM-113A + XX2 Beta/Gamma Survey meter - mostly as a display piece but one day I might be able to get it running, and having been bitten by the Geiger bug am keen to build a GK-Plus kit in the near future to act as a mobile hand-held counter using one of my SBM-20 tubes.


quiet1_au

Thanks mw0uzo - I'll give it a go!

Success! I'm using a cheap WizNet 5100 module off eBay with my GK-B5 & GKnet kits. This module is mostly pin-compatible with the ENC28J60 socket on the GKnet board - I took the precaution of cutting the tracks to the two PoE pins on the module and I still had to remove and replace the header on the underside of the board (which was harder that it appeared without decent de-soldering gear - I ended up having to bridge a gap to the Vcc pin after the through-hole plating was removed along with the pin...) I think the module itself could do with some support to keep it level under the weight of the ethernet cable, otherwise it was a success and an inexpensive option. The SparkFun board would have been a lot less work, plugging straight in without risky desoldering/resoldering, but sometimes you need to take the road less travelled...

I ran a quick test to make sure it was uploading data correctly - I decided to use "real" data (not the simulated test mode of the sketch) so used a Thorium gas mantle to generate a significant spike in the background radiation counts.

I'd appreciate some input as to the best CPM to uSv/hr conversion factor to use with my STS-6 tube for background work. The very informative DIYGeigerCounter site says:

SBM-19 (STS-6) - Well here's a fun tube! It's huge, cheap and very sensitive. I'm getting background in the range of 160 CPM. If you can spare the space this is a great tube for background. I found a few datasheets here and here. It's now added to the comparison charts. Compared to the SBM-20, it gives 5x the background (because of it's size), but only ~1.5x the readings for the other test samples which are more point sources. If I were using this tube for background, I'd use 5x the SB-20's rate of 175 or 875 CPM / uSv/h. For point sources I'd use 1.5x the rate or 263 CPM / uSv/h. (just my best guess )

I'd also welcome some feedback as to tube load resistance for the STS-6 - I've been using the standard 5(.7)M on the GK-B5 kit but wonder if I should add a little more (the specs from memory suggest 5-10M load resistance)?

I have both STS-6 and SBM-20 tubes (two of each) and Potassium Sulphate fertilizer (~2-3x BG count), a Uranium glass goblet (~10x BG count) and a Thorium-based gas lantern mantle (~100-200x BG count ) to work with, so is there a good way to do a reasonable calibration with these few sources without skewing the results too much with the difference in tube sizes vs source sizes? My initial impressions was that the background rate difference between the two tubes was lower than suggested 5x the SBM-20 . (Apologies for not RTFFAQ.... )