0t--Dalibor Farny's NASA Nixie instrument
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  1. #1
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    Default 0t--Dalibor Farny's NASA Nixie instrument

    Dalibor Farny is premier builder/restorer of Nixie apparatus
    he recently completed bespoke build of measuring instrument for NASA
    NASA specd Nixie display--like one used 50 years prior

    Farny instrument incorporates analog meter i have not previously encountered--displaying uncertainty

    Calibration display for NASA
    Attached Thumbnails Attached Thumbnails df1.jpg   df2.jpg  

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    Nixie tubes were probably the first electronic digital display. (There were mechanical clocks with digits as opposed to analog hands a long time ago.) However, in this application, they are absolutely not a relevant aspect of the instrument's function, and these Nixie tubes could have been replaced with LED digital displays with longer life, much higher reliability, and much lower power consumption.

    I do understand the "mil-spec" or "aviation certification" process requirement that says "This is the only authorized way to do it. So any repairs must do it the same way." But it seems unusually needless in this case.

    The exception would be if this instrument is primarily intended to be a museum piece, rather than a piece of lab equipment. In that case, a faithful restoration is indeed appropriate.

    From the labels, this device is obviously displaying a duration or time interval of some kind, with a range up to 1000 days and a precision of 1/10,000ths of a second. The "uncertainty" is labeled in microseconds with a log scale, and presumably is showing the current expected accuracy of the measurement (or conversion) process.
    Last edited by sfriedberg; 12-03-2021 at 05:25 PM.

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    Design looks like an old-school Mission Elapsed Time display. No need for that kind of thing to measure IRIG, but maybe I could see it useful for the camera testing mentioned if the nixie segments illuminate in some more suitable way than a LED. OTOH I wonder how much that really matters.

    IRIG is a reasonably convenient method to distribute time to a microsecond, back in the day used to propagate it over a wide geographical area. Nowadays its more a legacy thing, derived from GPS. It could be the uncertainty accumulates if the device freewheels, or perhaps indicates how well the device is synchronizing- the IRIG signal facilitates syncing down to microseconds. I wonder why bother with those small meters- even if the nixie tubes are important why not just put led digits in place of the meters so the exact values are known. And a massively awkward footprint too- should fit in a rack if its going to play in a real lab.

    I keep thinking whoever spec'ed it mostly is fixated on vintage looks.
    Last edited by Greg Menke; 12-03-2021 at 11:50 AM.

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    Super cool. I have an old DRO that uses some other type of filament based display - similar to a nixie, but not, as far as I can tell. Its a very old accurite if I recall correctly.

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    Balancing the propagation delay of integrated circuits, software latency, and Nixie tube responsiveness is a fairly unusual set of constraints. Kudos.

    Plus, Dalibor Farney will surely be a character name in the next Wes Anderson film.


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