[time-nuts] Capacitive temperature sensing
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sat Aug 23 10:57:35 UTC 2008
Hej Magnus
An elegant way of achieving some degree of temperature compensation may
be to use 3 coaxial electrodes surrounding the mercury column.
One relatively long one used to couple the bridge drive signal to the
mercury column and located between the other 2. The top electrode one
being used to sense the position of the tip of the mercury column and
the lower one as a temperature compensation element in the other side of
the bridge.
A phase sensitive detector with a suitable preamp could be used to
detect a capacitive null.
The phase sensitive detector output drives a PID or other temperature
control system.
Bruce
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