David W. Gulley wrote:

> Rex Byrns wrote:
>=20
>> Yes, CERAMIC resonator on a 16f84a at 20mghz.  The digikey part # is
>> X909-ND - it has caps and all in one package.
>=20
>=20
> The ECS ceramic resonator only has an accuracy of =B1 0.5% @25=B0C.
> That's about 18 seconds an hour!


I usually try to not reply to my own messages, but I just realized that=20
if you can control the temperature to keep it fairly constant (this=20
device also has a temperature sensitivity of =B10.3% from -20=B0C to 80=B0=
C)=20
you may be able to configure the 0 error timer based upon observed=20
frequency rather than specified frequency.

You can calculate the "observed frequency" from the time between actual=20
time and the time measured by the current circuit. If it is losing 20=20
seconds in 6 hours, change the counts to compensate.

The ceramic resonator may be stable enough for your purposes, if you can=20
keep it at a constant temperature.


David W. Gulley
Destiny Designs

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