[Weather] 1-wire humidity sensor for outdoor use?

[David Gibson/Portsmouth/IBM]

I don't know if this helps or not but my outdoor humidity sensor is the 
original one I got from Dallas, many years ago. Its still going strong, in 
a pagoda, and I am located about 1000 ft from the Atlantic Ocean. What 
sensor was it based on?

But I do wish that wserver didn't have all those drop outs. Happens on all 
humidity sensors I have. They can go for a few days sometimes, then 
suddenly start dropping out. Makes min and max worthless. As far as I know 
it is a network issue, if I have only one device on, its fine for as long 
as I have the patience to let it run. But there are more things in life to 
monitor...

David


weather-bounces+david_gibson=us.ibm.com at buoy.com wrote on 11/28/2006 
02:55:56 AM:

> [Nafis, Christopher A (GE, Research)]
> 
> > I've been using the AAG TAI8540 Humidity sensor mounted in a Davis
> > Radiation shield for an outside humidity/temperature sensor (AAG 
states
> > "designed for indoor use"). I've coated the circuit board with liquid
> > tape, but the honeywell sensor still seems to "die" after a year or 
so. 
> > Hobby Boards also sells the HT3-R1-A Humidity / Temp sensor with a
> > moisture resistant coating.
> 
> My Honeywell sensors usually don't last longer than half a year.
> After a while, I get 0% readings, or readings stuck at a certain %, or
> they indicate more or less random humidity.  Even new sensors using
> factory calibration are a problem; they sort of work, but without
> further calibration they may report more than 115% in heavy fog.
> 
> I've tried a lot of things: different shieldings, different boars (AAG
> indoor, AAG outdoor, Springbok), coating and heating.  The idea with
> the heating was to keep humidity well below 90% at all times and
> calculate the true rh based on the assumptation that the dew point in
> the heated box and in the ambient air is the same.  Perhaps the sensor
> would last longer, but I didn't get a useable accuracy.  Right now I'm
> trying to wrap a nylon sock (from old stockings) around the sensor
> (either the AAG enclosure or the sensor itself), which is suggested in
> the Weather Toys book.  So far it doesn't look too promising as it
> seems to make the sensor very slow and less accurate (though it seems
> to fix the problem with readings above 115%).
> 
> My conclusion is that the Honeywell sensor is fine for indoor use or
> in climates where humidity is always between 30 and 80%.  For coastal
> or mountain use, it's a constant calibration and maintenance
> nightmare.  I just had 10 days of continous fog and rain here (i.e. rh
> in the high 90's all the time and about 130 mm of rain/sleet and windy
> at times) and two newly mounted sensors that were matching eachother
> perfectly, were off eachother by 10 to 15% when the fog lifted and
> things dried up.
> 
> If anyone has any other ideas how to fix the honeywell sensor, I'm
> ready to try anything.  Or if anyone can think of a design using
> another sensor, I would happily switch to those if they're likely to
> need less maintenance, even if they're $200 each.  I can live with bad
> accuracy above 90%, if the sensor goes back to normal accuracy below
> 90%.
> 
> -- 
> Steinar
> 
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