Adi <adi@SL.LAKEHEADU.CA> wrote:

>I'll be starting on my weather monitoring system soon. Any
>suggestions for what to use for barometric pressure and humidity? I
>am using a LM35 for temperature and I like the idea of not having to
>do any calibrating. Are such things available for humidity and
>pressure?

For barometric pressure, I've been using a Motorola MPX5100A
sensor.  This is probably not ideal, since I'm only using about
15% of its range; nevertheless, it has adequate sensitivity for
0.01 inHg resolution.  The unit was within about 0.5 inHg using
data sheet parameters; finer calibration was accomplished by
comparison with a commercial weather station about 10 miles
distant.  The two track quite well, with rarely more than 0.02
inHg difference.

This sensor is available from Newark for about $26.

Steve Turner