[time-nuts] HP5065A environmental sensitivities

[timeok at timeok.it]

Hi Corby,

very interesting. I have some questions?

1) it is difficult to read the frequency value on the plot. Can you specify?
2) how do you set the offset of the op-amp trimmer ?
3) do you think is possible to use the -20V on the HP5065A instead the -12V from the DC-DC converter?
4) what frequency measurement system do yo have used for?

I am curious to know how you have generate the barometric swing.


thanks ,
Luciano
www.timeok.it


On Fri 13/05/16 03:29 , <cdelect at juno.com> wrote:

> HP 5065A Environmental sensitivity
> 
> First here is a comparison between the specified sensitivities of various
> 
> Rubidium units.
> 
> Barometric per mbar Temperature per degree C
> 
> HP 5065A 6.3X10-14 1.6X10-12
> M100 FRK 8.7x10-14 2.4X10-12
> LPRO 1.0X10-13 6.0X10-12
> FE5650A unspecified 1.1X10-11
> FRSC 1.0X10-13 1.1X10-11
> PRS10 unspecified 1.0X10-11
> 
> As you can see the HP specs are better than the others!
> 
> After much effort I managed to measure the actual sensitivity of a 5065A
> on my bench.
> It was much better than the spec at 1.55X10-14/mbar! I then installed
> a barometric compensation circuit consisting of a sensor and OP amp. This
> feeds the C-field circuit in the 5065A.
> After alignment the sensitivity was so low that it was below my
> measurement noise floor!
> 
> Attached is a frequency plot that illustrates the correction. On the left
> is a calibration offset from the Maser of plus/minus 1.84X10-12. The
> middle section shows the frequency with the compensation on during
> several cycles of plus/minus 35 mbar. The right is with compensation off
> and the plus/minus 35mbar excursions.
> 
> Also attached is a schematic of the compensation circuitry.
> 
> Now I'll work on the temperature sensitivity. Poul-Henning has explored
> in this area and has some good information to start with.
> 
> Cheers,
> 
> Corby
> 
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