[time-nuts] Is a crystal likely to change frequency by 3% ?
n1hac at dartmouth.edu
Fri Sep 12 23:04:54 EDT 2014
The battery probably was going weak and the oscillator coming out of
full control by the crystal. The tuning-fork crystal used in RTCs is
not as high-Q as a MHz crystal. I have noticed clocks using these can
go quite slow at low voltage. The crystal acts more like an inductor in
this case and resonates with the increased junction capacitance at low
On 9/12/14 6:52 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> Dr David Kirkby
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> Kirkby Microwave Ltd
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> On 12 Sep 2014 12:18, "Bob Camp" <kb8tq at n1k.org> wrote:
>> If this is an RTC, it’s probably running off of a battery when the
> machine is powered down. It is far more likely that the oscillator is
> dropping out (stopping) rather than shifting frequency.
> Good point, I never thought of that. I have however noticed that analogue
> quartz clocks slow as the battery goes flat. But maybe too they stop and
> start. It would make an interesting experiment to check it, but one would
> need some method of logging the time from the hands. Conceptually that is
> not difficult, but it needs more work than I want to do. One could do it
> with a video camera and a fair bit of work writing the software. Probably
> easier is logging battery voltage and current as that should show if it
> starts and stops.
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