[time-nuts] HP5065A environmental sensitivities

[Angus]

>when I made the correlation the best fit was obtained comparing a frequency difference data-set delayed 1 hour to the pressure measurements. But I have to dig into the data-set again – there might be an error calculating the MJD from Middle European Time.  As far as I understood from Corby´s measurements, the frequency reacts immediately to a pressure change without delay. For the compensation, a delay does not matter very much. Pressure changes are normally very slow.

I once tested an LPRO to measure the exact pressure sensitivity for a
analogue compensation circuit, and the data suggested a delay of
around 1/2 to 1 hour for best correlation between pressure and
frequency. 
Although the 3 LPRO's I tested were better that the Temex and 2
FEI5680's I also tested, there were still times that they did not
match quite so well, and for no obvious reason. 
I should try testing for a delay on some of the other data sets, but
since the reference for it was a M12+T, it's a problem extracting the
data from the noise.

>I know the SHT11 from the old days when a LPT-port could be controlled by the user.
>It is a nice device. But I bought the 144SC0811 which can be used by adding only one resistor.

I managed to get a cheap NOS one a while back too, but have not got
around to setting up a proper reference with it yet. It is not
affected by temperature too much, which makes it easier to use - but
considering the price they normally expect people to pay for it, it
should be good!

>It would be nice to see the results with temperature compensation. There are lots of sources producing temperature sensitivity. All have a different time constant. AS Poul-Henning found out, the rate of temperature change is the worst problem. In my eyes temperature compensation is much more complicated then compensation for barometric pressure.

In many regards pressure is simpler, but I do wonder if the mechanical
causes may just not be repeatable enough to properly compensate out. 
I've not seen much real detail about the exact causes of pressure
sensitivity in rubidiums.

Angus.