[time-nuts] Super stable BVA Quartz resonators... BVA??

Bernd T-Online BNeubig at t-online.de
Sun Dec 9 09:21:46 EST 2007


Tim Shoppa wrote:
> 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.
> I'm guessing the probe crystals were some special cut (don't know which!)
> which was fairly linear or at least monotonic over the measurement
> temperatures. I'm guessing that HP chose a cut which had a very large
> tempco such that tempco dominated over any frequency drift.

They did indeed. This was the HP2801A, later followed by the HP2804A.
It uses a so-called LC-cut (Linear Coefficient) quartz crystal sensor, 
which is a doubly rotated cut with ultra-linear frequency vs. 
temperature characteristic with a slope of 35.4 ppm/K.

For more information see http://hparchive.com/Journals/HPJ-1965-03.pdf

BTW: I proudly own a HP2801A plus two crystal sensor elements. However I 
cannot connect them to the instrument, because the 2801A has a special 
connector for it. It looks like a smaller version of a BNC connector, 
but the bayonet has three "nipples" instead of two. Does anyone on the 
list know what kind of connector that is and where to get the 
counterpart (plug)?

Regards

Bernd
DK1AG



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