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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