> On Tue, Dec 15, 2009 at 12:25 PM, AK <00@case.edu> wrote:
> > Haven't used it, but Honeywell makes a capacitive humidity sensor that
> > is just under $6. =A0With a bit of creativity and some functions from a
> > PIC: comparator, timer, A2D with thermistor - a cheap humidity sensor
> > could be devised. Alternatively you could build it into an oscillator
> > and measure the frequency. =A0With this sensor, calibration on a per
> > unit basis is required.
> >
> =

> I've used Honeywell capacitive sensors in the past, I don't have time
> to look up the exact number, but they are generally nice parts. I
> believe you can get pre-calibrated units. I'm not sure if this means
> they calibrate the units or tell you the calibration curve.
> (marginally useful in that case)

They tell you the calibration curve. Connect it to a PIC with an AD convert=
er =

and EEPROM to store the calibration data. You also need a temperature senso=
r if =

you want to do temperature compensation (not needed if the temperature is =

around 25 degrees C all the time). You also need the temperature sensor if =
you =

want to calculate the dew point temperature or the absolute humidity.

What is your application?

/Ruben
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D

-- =

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