Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

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bionerd23
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Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by bionerd23 » Sun Jan 15, 2012 1:04 pm

Hey folks,

I just received a Ludlum, Model 3.
I see Carl has successfully built a Soundcard-Spectrometer and used it e.g. in his trip to Chernobyl; however, he uses a Ludlum 12 which has a plug on the side that connects to the soundcard. My Ludlum 3 only has the one BNC connector where the probe plugs into.

However, looking at pictures of other Ludlum 12, it seems like this plug was not there originally but rather is a diy-mod.

Is it possible to add a pulse output to the Ludlum 3 as well?
If so, can anybody give me the lowdown on what I have to tap into? My electronics knowledge is rather basic, admittably, so I'm not sure if I could figure this one out by myself.

Thanks a lot for any advice!

David D Speck MD
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Re: Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by David D Speck MD » Sun Jan 15, 2012 3:11 pm

Illy,

If you post your question on the Geiger Counter Enthusiasts user group at:

GeigerCounterEnthusiasts@yahoogroups.com

I;m sure you will receive a response. The mod may already be present in the group archives.

Dave

Wilfried Heil
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Re: Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by Wilfried Heil » Sun Jan 15, 2012 5:06 pm

Here is the manual for the Model 3, which includes a full schematic.

You can pick off the pulses at pin 3 of the "accessory connector" P2.
Pins 2 and 6 are GND. (See p. 33 of the manual).

These are digital pulses only, useful for counting. The sound signal which goes to the speaker may be less suitable, because that is a short beep produced by a multivibrator.

http://www.drct.com/dss/INSTRUMENTATION ... manual.pdf

Dan Tibbets
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Re: Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by Dan Tibbets » Sun Jan 15, 2012 9:10 pm

I believe there are two simple programs available that will take the audio clicks from the detector fed through the microphone jack on the sound card, and record the data in a timely manner. Not as sophisticated as a good setup but it might do. I took the clicks from a Geiger counter, fed through a microphone, and it worked poorly. There was a lot of noise. But, when I used a cheap old Radio Shack audio amplifier the results were much better. Directly wiring the counter output to the audio (or microphone?) in port would work better provided they are compatible.
I found the two programs from this site. A search may find them though I don't know if the referenced links are still available.

Dan Tibbets

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Re: Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by Dan Tibbets » Sun Jan 15, 2012 9:21 pm


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Steven Sesselmann
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Re: Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by Steven Sesselmann » Mon Jan 16, 2012 2:14 am

Hi Illy,

Are you familiar with my Gamma Spectacular?

I have made over 250 of these USB powered scintillator drivers for use with PRA software.

More than happy to give a $50 discount to fusor.net forum members.

http://www.beejewel.com.au/research/Bee ... cular.html

Steven Sesselmann
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http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

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Carl Willis
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Re: Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by Carl Willis » Mon Jan 16, 2012 2:25 am

Hi Illy,

My mod's approach is pretty simple, but the specifics would depend on whatever ratemeter you are using. There are many different versions of the Ludlum Model 3 and Model 12, each differing in certain particulars like board layout and components used. All you want to do is trace the circuit back from the input coupling capacitor, through the first preamp stage, to the output of this stage or the second stage (if practical). Install a BNC connector in the shell of the Ludlum unit, wherever is convenient. Connect this BNC center conductor to the output of the preamp via a 0.1-0.01 microfarad capacitor, and you're ready to go.

-Carl
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TEL: +1-505-412-3277

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Re: Soundcard-MCA using Ludlum Model 3 (+NaI(Tl))

Post by bionerd23 » Sat Jan 21, 2012 8:37 pm

Thanks everybody for the many hints and tips!

Tomorrow, I will try to roughly get Carl's version of the mod to work.

If that fails, well, I will look into the other suggestions. I currently cannot afford to pay $200 for the "Gamma Spectacular", so I'll look into the DIY style for now. Thanks, Steven for the discount, anyway!

If anybody is wondering, I am exchanging the Ludlum for a NaI(Tl) probe and a piece of Be foil, so that technically didnt cost me money, at least not recently.

Here's an operating voltage calibration graph for now. Seems these two equal probes have quite a different gain, and the plateau of probe #1 is by far not as nice. Nevertheless, both probes are quite ideally in the first third of the plateau at the CDV's operating voltage of about 900 volts... The input sensitivity, however, is vastly different. Just thought I'd share, as I found it interesting.
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