# What is PPM with regards to crystal tolerances

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

1. ### keanGuest

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

kean, Jun 22, 2004

2. ### ArtGuest

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" <> wrote in message
news:...
> 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, Jun 22, 2004

3. ### ExternetGuest

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

Externet, Jun 22, 2004
4. ### ZorknobGuest

(kean) wrote in message news:<>...
> 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.

Zorknob, Jun 22, 2004
5. ### Rich GriseGuest

"kean" <> wrote in message
news:...
> 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

Rich Grise, Jun 23, 2004
6. ### keanGuest

"Rich Grise" <> wrote in message news:<UT5Cc.23892\$>...
> "kean" <> wrote in message
> news:...
> > 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.

kean, Jun 23, 2004
7. ### Robert BaerGuest

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...

Robert Baer, Jun 23, 2004
8. ### David L. JonesGuest

"Rich Grise" <> wrote in message news:<UT5Cc.23892\$>...
> "kean" <> wrote in message
> news:...
> > 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

David L. Jones, Jun 27, 2004