RE: Humidity sensor - Electronics expert required!

["Keith Doxey" <keith.doxey@xxxxxxx>]

Hi Julian,

The 47uF capacitor is probably to provide some smoothing to the output so
you dont get sudden spikes or drops in the reading. Any permanent change in
the output will be accurately shown within a couple of seconds. The
resistor
will be to leak the charge away from the capacitor otherwise the reading
may
never fall to zero!

Think of it as an averaging circuit. It will hide any sudden changes but
will track the trend giving a truer reading overall.

You could probably omit them but then you would have to write your program
to take spurious readings into account.

The above is pure speculation based on your description......a link to the
datasheet would have been nice :-)

Keith





-----Original Message-----
From: Julian Driver [mailto:julian@xxxxxxx]
Sent: 29 August 2000 19:05
To: ukha_d@xxxxxxx
Subject: [ukha_d] Humidity sensor - Electronics expert required!


I am all set up to connect a humidity sensor to my Homevision. It has
connections for +5v, ground and an output voltage of 1 to 3v
proportional to humidity. So far so good.

The measurement circuit in the datasheet however has the output
connected to ground via a 47 microfarad capacitor and a 100K resistor
connected in parallel. My question is What do these do, and do I need
them with HV?

(I tried to draw it but the result in ASCII is too embarrassing for
words.)
--
Julian Driver






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