Crystal oscillator frequency stability?

youl find it varies with many things :- temperature at a certain rate, supply voltage at a certain rate and ageing over long time at a certain maximum rate, plus the initial accuracy, all this in total will probably be less than +-100ppm. (and also acceleration too ! but this probably isnt included) so dont expect to see any such wild variations in the space of a second or two.

Colin =^.^=

Crystal stability is normally quoted over the specified operating temp range.

So, +/- 100 ppm over the range from 0 to 70 C equates to roughly +/- 3 ppm per degree C. This is an average figure and it may well be that it is much better at a particular temperature - like around 20C.

Don't forget the initial accuracy figure too and the fact you can usually tweak a crystal onto its marked frequency with a little capacitive loading.

It follows, that if you can keep the temp of the crystal stable, its frequency is very stable.

....... Phil

That's typical for a cheap can oscillator; they're usually within 10 ppm of dead-on. But they only guarantee +-100 PPM.

But from that initial value, expect a few PPM drift per year and a good fraction of a PPM per degree C (much less if you're lucky) and some more power supply voltage influence. But short-term, stability should be better than 0.1 PPM, even for a cheap rock.

John

On Feb 18, 8:33?pm, snipped-for-privacy@yahoo.com wrote: But when I connect the output to a frequency counter it reads

Do not forget, your counter also has a timebase. You must consider the drift and age of that timebase (probably crystal derived?) on your quoted measurement. It could be that the crystal is dead-on, and the instrument is 60 Hz "off".

In reality, it is highly likely that they are both "off", at least a little...

Convert these numbers to percentages and you will discover that for most circuits, the accuracy is plenty sufficient.

-mpm