Relative Humidity Sensors

[Tom Droege <droege@wwa.com>]

It looks like the basic scheme for measuring relative humidity is to use a
capacitor sanwidch made up of two plates with a special polymer in between.
 As the polymer absorbes moisture, it's dielectric constant changes, and
thus the capacity of the device.  Unfortunately I am set up to measure
voltage, not capacity.  I know how to do deal with this type of device, but
not in the Mark IV.  So the best suggestion is that of jamie who said go to
Radio Shack and buy their device.  Unfortunately it has a digital meter on
it.  The hope would be that I can find inside where they have a voltage
proportional to the RH.  Hmmm!   This is beginning to look like a bigger
project than I would want.  

BTW, those interested can look at:

http://www.protimeter-usa.com/Support/supcmth.htm

and see that Bob Dubner's light on a mirror device is actually a commercial
product.

Why to most of my search efforts for RH end up in Vantaa, Finland?  The
Vaisala Co. has a page showing their relative humidity in real time.  Looks
like in Finland you discuss relative humidity instead of the Bulls.  

Tom Droege