Ricardo, I'm working on a 16C74-based weather station and I've looked
at a variety of humidity sensors. Low-cost sensors behave like capacitors
that vary with humidity to change the frequency of an external oscillator.
Typical relative humidity ranges from 10 - 90%. In addition to the other
sensors mentioned, Philips makes a low-cost sensor (P/N 2322 691 90001).

   For my project, I needed better accuracy and I wanted to reduce the
complexity of the support circuitry. I ended using HyCal sensors which
provide an output within 0-5V and require minimal support. The outdoor
sensor is an IH-3602L which comes in a T0-39 can with a slotted cap and
for the indoor sensor, I used the IH-3605 hybrid element. Both sensors
operate from 0 - 100% and provide an output from around 0.8V - 3.9V with
a 5V supply. They require a simple low-pass filter and, as with most
sensors, need to be shielded from sources of bright light. You do need
to factor in temperature compensation so you need to measure ambient
temperature near the sensor.

   For more info, contact:

      Philips, (817) 325-7871
      HyCal,   (818) 444-4000

   - Tom

At 10:14 AM 5/11/97 -0300, you wrote:
>        I'm looking for a humidity sensor.
>        Anybody know?
>        Thanks
>        Ricardo
>        rcbarbosa@riopreto.com.br