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Deciphering other's prototypes: Mystery NIM module
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ChristofferB:
Hey all!
I've recently scored a NIM bin full of Ortec spectroscopy amps/analog delay/gating and HV bias stuff, which I believe has been used for gamma spectroscopy at a hospital once.
Here's the strange part: There is one home-brew prototype module in the rack. It is a single width NIM box with 6 BNC's and a switch on the front, two BNC's on the back and a big ribbon cable crudely cut off.
See attached pictures. It would be interesting to figure out what it's supposed to do.
Here's what I know:
- It has two input channels, going through the OP07 op amps on top of the perfboard, and two bnc's just heat shrunk to nothing, likely from test setups.
- The BNC's are just labeled (with pencil) (top-bottom) 0,1,2,3, trig. Last one has no ID. The toggle switches between pos/neg.
- Two BNCs on the back are labeled bit 0, bit 1
-The 74LS320 clock generator is driven by a 10 MHz crystal, and feeds LS592 timer, whose preset bits are fed to the ribbon connector.
-Two of the voltage regs (78/7915) aren't used ? PSU in is +-12V and is regulated to 5V for the logic
It looks a little incomplete but again, this was a working instrument, as far as I know, not some leftover from a university project, so it must be assumed the module preformed some task in its current state. Since this is a energy spectrometer (probably) it would make sense if there was some sort of ADC involved.
Could this be some sort of crude, discrete delta/sigma ADC?
I don't think getting the module working is an option, but it would be interesting to know what's going on.
I hope you think so too!
--Chris
ChristofferB:
From the IC's, it actually looks like a Wilkins type ADC. From what can be seen in this block diagram (attached).
I found a great scanned book "Nuclear electronics laboratory manual" published by the IAEA:
https://www.iaea.org/publications/786/nuclear-electronics-laboratory-manual-1989-edition
And WOW. it is a great resource. First of all it's a complete analog/digital electronics introductory book, but always with the focus on nuclear/particle like instrumentation. Secondly, a lot of specific circuits and functions like single/multichannel analyzers, spectroscopy amplifiers, pole zero cancellation circuits etc.
ChristofferB:
After some preliminary analysis, it seems the heart of this thing was whatever was on the other end of the ribbon cable.. The input amplifiers feed directly into the cable, so does the preset bits from the counter and the two BNC's on the back.
The only function that looks like it would be working is that a pos/neg trig pulse would produce a fixed lenght TTL pulse on the lowest front BNC.
Either way I don't think I'll sacrifice more time on it. I just wanted to be sure the only value of this is to reuse the box and BNC's.
It was an interesting excersize, anyway!
--Chris
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