Re: Calibration Of Electronic Equipment In The Home Workshop

doug wrote:
Anthony Fremont wrote:

Like my analog/quartz watch that has a predictable error. I used the
CCP module to time the impulses to the watches stepper motor to the
uS. I already knew the error rate of my watch, so I just played
with the loading caps until I knew that I was sucessfully measuring
the error of my watch over hours of time. Since my house stayed at
a fairly consistent temperature, I think it's safe to say that it
was within 2ppm, but I guess I could be wrong.

This is a dangerous way to calibrate crystals. The temperature
coefficient will give a drift with temperature of up to around
100ppm. I you breathe on the crystal it will go out of spec. If

I don't know about that, the crystal is alread rated at that over a fairly
wide temperature range. I had in a room that only varied by a couple of
degrees. At any rate, is was just for fun to see how close I could get it.

you want to try this, put a crystal oven on the crystal. There
are temperatures where the frequency versus temperature is flat
and an oven will give you a stability of maybe a part in 10^7 or
so. Then you can do a calibration. Why not look on ebay for an
old hp counter such as the 5328 which often come with a very nice
oxco which is good to up to 10^-8 for maybe a year? I have paid
as little as $50 and then you even have a counter to go with it.
The 5334 are newer, nicer and quieter but may run a bit more.

I think you misunderstand my intentions. I wasn't trying to use if for
anything important, I was just doing my usual tinkering. At any rate,
thanks for the model information. I will look around. I already have an
old Protek 1GHz counter, but it needs a cal too.


.

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