PPM error calculate formula

Discussion in 'Homework Help' started by sen_embedded, May 10, 2010.

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  1. sen_embedded

    Thread Starter New Member

    May 9, 2010
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    Crystal frequency = 32.768KHZ
    PPM =20 PPM
    Temperature =25 C

    I have used above crystal in RTC. I am getting 1.4 sec delay per day can you please let me know how calculate the error.

    Please let me know PPM error calculate formula
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    The error is 1.4 sec per 24 hours

    Error[PPM]=1e^6*1.4/(24*3600)=16.2037 PPM

    which is within the error spec. of 20 PPM @25C for your crystal.
     
  3. sen_embedded

    Thread Starter New Member

    May 9, 2010
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    Actualfrequency = 32768 (Hz)

    20 ppm frequency =32768-20 = 32748

    Actualfrequency per day = 32768 * 3600 * 24 = 2831155200

    20 ppm error frequency per day = 32748* 3600 * 24 = 2829427200


    Error frequency per day = 2831155200 – 2831068800 = 1728000 Hz /per day


    frequency = 1728000 /1000000 = 1.74 sec

    20 PPM error in 32.768 Khz. crystal oscillator = 0.5 Sec per day


    Pelase let me know my caluation is right or worng
     
    Last edited: May 10, 2010
  4. Markd77

    Senior Member

    Sep 7, 2009
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    Crystal frequency is irrelevant.
    Max error per day is (60*60*24) * (20/1000000) = 1.728
    ........................seconds in day * error
     
    Last edited: May 10, 2010
  5. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    If you want ultimate accuracy, use a crystal that needs a higher capacitive load that the oscillator in the chip provides; ie. the common crystal osc config with a capacitor to ground from either side of the crystal.

    Now make the capacitor at the oscillator input side a variable one - a trimcap, of about twice the nominal fixed capacitor value.

    You can then tune the oscillator to exact frequency and minimise any error.

    If you need better stability still, you also need to temperature stabilise the crystal, or preferably the whole oscillator circuit.
     
  6. retched

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    Dec 5, 2009
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  7. Martino Chiro

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  8. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
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    What is PPM here?
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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  10. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
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    anyway what is it?
     
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Open a new thread if you have a question.
    Isn't that what you always do.
    Better yet type that in google and read the articles for a change.
    You are not a baby to ask things that you can find for your self.

    https://www.google.mv/?gws_rd=ssl#q=PPM+crystal+error

    I get tons of info and why can't you. Don't be lazy. Try to read for your self.
    What makes you think you would understand any better here than from google.....!
     
    RRITESH KAKKAR likes this.
  12. WBahn

    Moderator

    Mar 31, 2012
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    MOD NOTE: Thread closed -- necroposting.
     
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