[time-nuts] Super stable BVA Quartz resonators... BVA??
Javier
javier at nebulosa.org
Sun Dec 9 08:36:54 EST 2007
Tim Shoppa escribió:
> For a while, didn't HP sell temperature probes which were in fact
> quartz crystals? Oscillation frequency was converted by some simple
> electronics to a temperature, and at the time (60's?) they were
> exquisitely convenient for measuring way better than a tenth of a
> degree.
>
>
> Either the frequency drift was negligible or it
> was so slow that I don't remember any manual removal of frequency
> drift effects.
>
>
At least one model is the 2804A. Not much info about it in the Agilent
web site, but according to the 1986 catalog 'the temperature sensor is a
quartz crystal whose precise angle of cut gives an stable and repeatable
relationship between the resonant frequency and temperature'. But also
is mentioned there that 'The only adjustment necessary to remove effects
of thermal history on the sensor is a simple ice point or triple point
calibration adjustment using the front panel thumbwheel switches'.
Since the ice-point calibration would only be able to remove an offset,
I understand that this is the manual removal of frequency drift effects.
Of course, I suppose that the dritft would be small compared with the
quartz temperature coefficient. Anyway, a 10544 oscillator has a cold
offset that can easily be of 1000Hz, so if at 80 deg. C the offset is
zero, and at 25 deg. C the offset is 1000Hz, you easily have a rough
15Hz/deg C average tempco in that range - and the aging drift for this
oscillator is quite less than that.
Best regards,
Javier, EA1CRB
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