Electronics Forums > What is PPM with regards to crystal tolerances

# What is PPM with regards to crystal tolerances

kean
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Posts: n/a

 06-22-2004, 10:08 AM
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

Art
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Posts: n/a

 06-22-2004, 11:21 AM
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.
"kean" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> 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

Externet
Guest
Posts: n/a

 06-22-2004, 03:31 PM
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

Zorknob
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Posts: n/a

 06-22-2004, 03:38 PM
(E-Mail Removed) (kean) wrote in message news:<(E-Mail Removed). com>...
> 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

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.

Rich Grise
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Posts: n/a

 06-23-2004, 02:27 AM
"kean" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> 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?

100 PPM == 0.01%

Cheers!
Rich

kean
Guest
Posts: n/a

 06-23-2004, 06:17 AM
"Rich Grise" <(E-Mail Removed)> wrote in message news:<UT5Cc.23892\$(E-Mail Removed)>. ..
> "kean" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) om...
> > 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?

>
> 100 PPM == 0.01%
>
> Cheers!
> Rich

Okay!. Thanks a lot for the help guys.

Robert Baer
Guest
Posts: n/a

 06-23-2004, 09:02 AM
kean wrote:
>
> 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

Be advised that 100ppm is crappy; a good RailRoad watch does better...

David L. Jones
Guest
Posts: n/a

 06-27-2004, 02:32 PM
"Rich Grise" <(E-Mail Removed)> wrote in message news:<UT5Cc.23892\$(E-Mail Removed)>. ..
> "kean" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) om...
> > 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?

>
> 100 PPM == 0.01%
>
> Cheers!
> Rich

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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