[time-nuts] HP5065A environmental sensitivities

[cdelect at juno.com]

Luciano.

Hi,

1) it is difficult to read the frequency value on the plot. Can you
specify?

The plot is averaged to get the signal out of the noise, The P-P
calibration offset on the left allows you to estimate the deviation of
the other parts of the plot. The short term stability of the 5065A at 1
sec is causing the noise you see.

2) how do you set the offset of the op-amp trimmer ?

The trimmer is set for zero out of the op-amp at ambient pressure, this
allows the output to be plus/minus,
not critical just zero it after you install it.

3) do you think is possible to use the -20V on the HP5065A instead the
-12V from the DC-DC converter?

Probably would work fine as the load on the minus side is just the op
amp.

4) what frequency measurement system do you  use?

The maser is input to one side of a DMTD unit, the 5065A at about a .5Hz
offset via the  A1 synthesizer
is input to the common oscillator input of the DMTD. This setup give a
SMTD configuration.
A ping-pong counter then feeds a laptop.
A good quartz can be used instead of the Maser but WILL show up as drift
in the plot.

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

Put the 5065A in a sealed box (easy to say hard to make work!), zero the
op-amp, run pressure up to .5PSI (-160mv at op-amp), then when done
reverse pump and pump down to -.5PSI (+160mv at op-amp). When done remove
pump and go back to ambient pressure. (I used a 12 Volt pump used to
inflate/deflate an inflatable bed, also used a variable supply into the
pump to allow setting the pressure/vacuum)
The box I made has a LARGE two sided heat sink on the lid, one heat sink
goes down into the box and the other is outside. This allowed me to keep
the 5065A at around 44 degrees C during the tests. (box stayed sealed for
a couple weeks while I generated data.) This box will also be used for
the temperature testing.

The SBT R7 resistor is used to set the P-P current change generated by
the +-160mv output to match the P-P frequency excursion caused by the
same. Being of opposite polarities they will then cancel out any
barometric changes.

Cheers,

Corby