>Thanks for all the suggestions. The variable capacitor idea is one that
>Mr. baldwin also suggested. Not that his idea needed validation, but
>repeat hits generally tell me that I have been overlooking a potential
>winner.

Not to revive the thread but it really depends on what you are most
familiar with. Variable capacitance is very low power (if you know how to
use it). Optical is easy (you could use 2 polarizers instead of an
optically graduated disk - this is SIGNIFICANTLY more linear than any
graduated disk you can buy for normal money), but requires more power.
Variable inductance (variometer) is also low power and can be done at
mains freq. (if you have it), or higher, but it requires coils. Most
people hate coils for some reason (I do not ;-). There is also magnet +
Hall sensor (linear). The magnet rotates and the Hall sensor gets a
cos(phi) output. This could give you high resolution at low pressures and
low at high #. The same effect can be arranged with variometer and
variable capacitor methods.

good luck,

Peter

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