[time-nuts] Is a crystal likely to change frequency by 3% ?

David Kirkby david.kirkby at onetel.net
Mon Nov 26 14:12:18 UTC 2012


I've got an HP 8720D VNA. This has been out of support from Agilent
for 8 years, so its getting on a bit. There's a clock in the
instrument which keeps the date and time. This is losing about 1 day
per month (rough guess), so it has slowed by a bit over 3%.

I'm guessing this is likely to be a battery running flat, but are
there any other likely causes? I know crystal can jump in frequency,
but I'm guessing not by 3%, but perhaps if there was stress in the
crystal, it might be.

It does not help the fact I can't find a service manual for this
instrument. It's also a fairly expensive bit of kit (I paid $16,000 a
few months back), so I'm not keen to screw it up. If need be, I'll
write a bit of code which sets the clock from my computer whenever the
GPIB is used. I've no need for precision time keeping on this, but it
would be nice to have a copy of the date and time on any printouts.
That's not possible when the clock runs so slow.

On the off chance anyone does have a service manual for an 8720D,
please let me know. I'll buy a copy if need be. There is not one on
the Agilent web site - only the user manual.

Dave



More information about the time-nuts mailing list