For anyone interested, there is a Cs137 source lost somewhere along 870km of Australian highway. No mention of actual strength but supposedly it is equivalent to 10 x-ray imaging's per hour. It would make a nice source for your project. 
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Needing more than a spark test?
- Thread starter graham-xrf
- Start date
I think the plot is dosage vs. time. If well calibrated it's not a bad deal.
At least we can show it a smoke detector, and maybe get a count/sec, even if we have to use a smartphone recording. I am tempted.
Looking at your ionization chamber detector circuit also gets me thinking. I have a ex-Ukrainian Geiger tube.
I think it's the more sensitive version, but I also think it needs more than 50V
Here's a totally different kind of question. What do folks think of the following ADC? It's differential input, 16bit SAR, 1Msps, using SPI. 1MSPS 16 bit SAR ADC A 30MHz SPI clock will give you 500 Ksps, but it can run using a 60MHz clock. Technically a Teensy tops out at 30MHz according to the datasheet, but will go faster. I'm about to test that now. I will test it writing (to my display!) at 60MHz, I hope. Someone has made it work with a Teensy at 30MHz. I don't know about higher speeds. I can report at least the display will write at 60MHz. I can see the 60MHz clock on my scope.
It's a small package MSOP-10, with leads! and the 1MSPS part is $9.19 in unit quantities.
It's a small package MSOP-10, with leads! and the 1MSPS part is $9.19 in unit quantities.
It has some reasonable specifications. It comes in 16, 14, and 12-bit types, but I assume you mean the MCP33131D-10, meaning 16-bits 1MSPS.
That one claims 91dB SNR, same as the Analog Devices ADCs we are using.
It will need the differential driver circuit, or something like it, as shown in #1384. That's OK
It needs an external reference. For this kind of critical measuring, you can't use just any old power rail. A built-in precision bandgap reference was one essential feature I wanted when I was trawling for ADCs.
The price means that the cost of a separate reference is somewhat covered.
The price is right, that's for sure!
I don't think I will be clicking the pay icon for --> https://www.aliexpress.com/item/1005004817721983.html?
Hardball guys like us want to know curies (Ci), or becquerels (Bq) , meaning decays/sec
1 curie = 3.7 x 10^10 disintegrations per second = that same number of becquerels.
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The AliExpress gadget with glitter is a dose meter. Everything seems to be in uSv.
Sieverts, or micro-sieverts is all about body exposure.
Sv = 100 rem.
rem = rad x Q]
Q = a "Quality factor". Taken as 1 for beta and gamma, and 20 for alpha
Then there are Grays (Gy) = 100 rad.
None of this stuff is useful to what we want to do.
Hardball guys like us want to know curies (Ci), or becquerels (Bq) , meaning decays/sec
1 curie = 3.7 x 10^10 disintegrations per second = that same number of becquerels.
--------------------------------------------------------------
The AliExpress gadget with glitter is a dose meter. Everything seems to be in uSv.
Sieverts, or micro-sieverts is all about body exposure.
Sv = 100 rem.
rem = rad x Q]
Q = a "Quality factor". Taken as 1 for beta and gamma, and 20 for alpha
Then there are Grays (Gy) = 100 rad.
None of this stuff is useful to what we want to do.
A little way down that page it has a figure showing some of the dose meter's functions. The "unit settings" option for the gadget includes CPS and CPM which would be more suitable for our purposes. No weighting, just counts.
OK then - suppose I get one, and I let you guys know what happens when I show it my sources. The AliExpress sources will arrive soon. We can discover if they are "feeble". Basically, I give it a run, and then review. If it's any good, those that want, can decide to get their own, if they are minded to.
I still think your ionized chamber circuit is pretty good, and I am surprised that it only needs 50V to work.
It's not like a geiger counter, which is a kind of avalanche multiplication scheme.
Some of the ionization chamber detectors I found on the internet used even lower voltages to sweep the ions to the collector, so the lifetime of the ions must be fairly long. At least, in the absence of smoke!