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What is PPM with regards to crystal tolerances

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

  1. kean

    kean Guest

    Hi,
    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?

    Thanks,
    Kean
     
  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.

    Miguel
     
  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%

    Cheers!
    Rich
     
  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
    temperature.
    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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