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Oscillator precision and marking on Fox crystals?

Discussion in 'Electronic Components' started by [email protected], Jan 17, 2006.

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  1. Guest

    I've got some Fox crystal oscillators that are marked as
    "50.000000MHz" (six places after the decimal!) yet these are standard
    +/- 100PPM parts. Either the Fox guys slept thru their high school
    chemistry lecture on significant digits, or I'm clueless, but this
    seems like way too many decimal places.

    I've got lots of other oscillators from other manufacturers that are
    marked as "50.000MHz". That's still pushing it a bit for 100PPM, but
    it's a lot more reasonable.

    Does this marking mean something that I don't understand?

    Bob Armstrong
     
  2. Tim Shoppa

    Tim Shoppa Guest

    Does this marking mean something that I don't understand?

    It means that it complies with the Fox standard for marking frequency
    on that size oscillator.

    Look around their website - the through-hole canned oscillators usually
    show six digits after the decimal point.

    (Although you will also find 0.5ppb OCXO's that only have three decimal
    points.)

    My conclusion is that the number of decimal points has nothing to do
    with accuracy or precision, and everything to do with the space
    available on the can.

    Tim.
     
  3. Guest

    It means that it complies with the Fox standard for marking frequency
    Bummer - I would have expected more from engineers. They would have
    flunked any science class in my high school, let alone college.

    When I was in high school, students would do their labs and take
    measurements with meters, scales, balances, etc that had two or three
    significant digits at best. Then they'd punch them into their
    calculators and put results on their lab reports with eight or ten
    decimal places. Completely bogus ...

    My chemistry teacher was especially a fussbudget about it. Failure
    to carry the correct number of significant digits was an automatic zero
    score on that question. For that matter, so was failure to carry the
    units all the way thru the calculations.

    'Guess I'm officially a curmudgeon :)

    Bob
     
  4. Bob,

    This wasn't a problem when I was in high school. Slide rules don't give
    you more than three digits of precision. I can still remember taking a
    test using my HP-35 calculator in college and writing down 2.9999999 as
    the answer before I realized that the answer really was 3.0.
     
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