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What is PPM with regards to crystal tolerances

Discussion in 'General Electronics' started by kean, Jun 22, 2004.

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  1. kean

    kean Guest

    Looking at datasheets for crystals, they specify its tolerance as +/-
    100 PPM. What does PPM stand for and how do you calculate the
    tolerance of the crystal in terms of frequency?

  2. Art

    Art Guest

    Parts Per Million: General reference to tolerance of the crystal frequency.
    1.00 MHZ Xtal with +-1PPM would therefore be plus or minus 1 hertz to be
    within that specific tolerance.
  3. Externet

    Externet Guest

    Hi Kean.
    PPM is parts per million.

    Is like percentage, but per million instead.

    On a ±100 ppM tolerance, means a 1 MHz crystal can be anywhere in the
    range of 999 900 Hertz to 1 000 100 Hertz.

  4. Zorknob

    Zorknob Guest

    PPM = parts per million

    With a +/- 100ppm tolerance, a 1MHz crystal can range in frequency
    from 999,900Hz to 1,000,100Hz. Where the crystal oscillates within
    the range is primarly a function of temperature.
  5. Rich Grise

    Rich Grise Guest

    100 PPM == 0.01%

  6. kean

    kean Guest

    Okay!. Thanks a lot for the help guys.
  7. Robert Baer

    Robert Baer Guest

    Be advised that 100ppm is crappy; a good RailRoad watch does better...
  8. PPM can refer to the temperature coefficient as well, so in this case
    it's not just an absolute frequency error, but a variation with
    100ppm/degC will give you 0.01% change per degree C. A big change if
    you are working over a wide temperature range.

    Dave :)
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