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Resonator Tolerance

Discussion in 'Electronic Design' started by [email protected], Apr 24, 2006.

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  1. Guest

    Hi,

    I have some questions on Resonator Tolerance, and PPM.

    On an engineering specs, it's mentioned that the initial tolerance is
    0.50%. How do you convert to PPM?

    How do you calculate the timing (microseconds) when the following are
    given?
    - 50ppm
    - 16MHz

    Thanks,
     
  2. Tim Wescott

    Tim Wescott Guest

    PPM means "parts per million", i.e. 1PPM means 1/1000000.

    % means "per cent", or "parts per hundred" in english. 1% means 1/100.

    I will _not_ do the math for you.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com

    Posting from Google? See http://cfaj.freeshell.org/google/
     
  3. Guest

    i know ppm and %

    but i can't figure out why 50ppm = 0.5%

    to my calculation, 50 ppm = 0.005%

    and 0.5% = 5000ppm


    my friend just said, simple divide/multiply by 100, i just don't get it,
     
  4. Guest

    that's only the first part,

    How do you calculate the timing (microseconds) when the following are
    given for a given duration?
    - 50ppm
    - 16MHz
     
  5. Guest

    A 16MHz waveform repeats every 62.5nsec. If there is a 50ppm tolerance
    on the frequency, there will be a 50ppm tolerance on the period, which
    is 3.125psec.

    This sort of question should be posted on sci.electronics.basics, or -
    better - dealt with by your instructor, who is paid to sort out this
    sort of elementary problem.
     
  6. Phil Allison

    Phil Allison Guest

    ** Shame you got crap replies from others here.


    ** That equates to 5,000 ppm.

    Or +/- 80kHz in a 16 MHz device.




    ** The " 50ppm " figure describes the *temperature stability* of the
    resonator.

    Very likely + 50 ppm change *per degree C * !!!

    The timing tolerance is dominated by the initial tolerance of +/- 0.5 %.





    ........ Phil
     
  7. Guest

    Hi Bill,

    Thanks, for the explination, I have tried to figure out by myself, but
    it didn't work.
    And no, I don't have an instructor.
    the tolerance be?
     
  8. Guest

    Thanks Phil~

    So if the 50ppm refers to changes of the tolerance by the degree, then
    i think i would look at the initial tolerance, :)

    thanks~ :)

    btw, how do i know what is the tolerence in seconds for a given signal?
     
  9. Guest

    A 16MHz waveform repeats every 62.5nsec. If there is a 50ppm tolerance
    on the frequency, there will be a 50ppm tolerance on the period, which
    is 3.125psec.

    or should i say that, there an timing tolerance of 3.125psec on the
    waveforms that i measured?
     
  10. If the timing tolerance is 50ppm, meaning a 20000th, then the time
    measurement can be off for 1 second every 20000 seconds.

    Rene
     
  11. Phil Allison

    Phil Allison Guest


    ** There is no "given signal".

    You are MASSIVELY fucking confused.




    ........ Phil
     
  12. wrote...
    If you have a recent vintage digital scope, it may be able to
    make quasi-accurate measurements for you, but an analog scope
    most likely cannot get you much past 0.5%, you'll be measuring
    the scope not the component. Go grab a frequency counter.
     
  13. Pooh Bear

    Pooh Bear Guest

    wrote:

    This is done using mathematics ! Multiplication and division - that kind of
    thing you know.

    Graham
     
  14. Pooh Bear

    Pooh Bear Guest

    It isn't.
    Your 'friend' was wrong.

    Graham
     
  15. Guest

    Hi Graham,

    Thanks for the clarification. I thought I was missing something in
    maths.
     
  16. Guest

    Hi,

    Let me paint the picture again.

    I am measuring the "waveform" from GoLogic. The waveform doesn't not
    tally with the values being flash into the device that is used to
    produced the waveforms. It devaites by a few microsecs.

    I was given that the device resonator's initial tolerance is 0.5%.

    But 0.5% of what? Of one message frame? Of one OnTime? OffTime? Or
    OnOffTime?

    So, how do I make use of the 0.5% tolerance to calculate the range of
    timing (in terms of +/- XXX microsecs)
     
  17. All of the above, modulo jitter in the oscillator etc. It's all
    proportional, so percentages stay the same.
    Suppose the time would be YYY microseconds (say the division
    ratio isn't exact so perhaps not exactly equal to what it would
    ideally be), the range of timing is YYY*0.995 to YYY*1.005,
    ignoring any jitter. The range in error is the difference between
    the ideal value and the above range of values.

    With asynch serial RS-232 type communications the error in the bit
    position of the last bit is what you normally need to worry about
    (because it's the worst case situation), and it's about 10 times the
    error in the timing. So with a 0.5% resonator and perfect division
    ratio you'd have about a 5% error in the middle of the last bit time
    when the sampling takes place (assuming no jitter, perfect edges, and
    no error at all in the other side).

    Best regards,
    Spehro Pefhany
     
  18. Guest

    Hi Spehro,

    Thanks for the explination.
    I'm using the USB version of GoLogic.

    btw, you mentioned that the timing would be YYY +/- 0.5%. So if my
    OnTime is 100us, so it should range from 95us to 105us. But I always
    thought the 0.5% should be for the whole frame or the whole message
    transmitted.
     
  19. Phil Allison

    Phil Allison Guest


    ** You really are a complete goose.

    Even basic arithmetic is beyond you.






    ......... Phil
     
  20. Guest

    Hi Spehro,

    You mentioned timing, but timing of the what?.....
    - onTime
    - offTime
    - OnOff Time
    - frame?.....

    btw, my friends speculate that the initail tolerance that is spec in
    the datasheet (0.5%) is for one OnOff Time.

    and said that the 50 PPM is refer to 50 pulses in 1 million, will out
    of out the specs......

    I'm not sure what to take...
     
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