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

[Steinar Midtskogen]

[Karl Uppiano]

> ----- Original Message ----- 
> From: "Dave McGuire" <mcguire at neurotica.com>
> To: "List for 1 Wire Weather Stations and devices" <weather at buoy.com>
> Sent: Tuesday, November 28, 2006 1:10 PM
> Subject: Re: [Weather] 1-wire humidity sensor for outdoor use?
> 
> 
> > On Nov 28, 2006, at 3:33 PM, Karl Uppiano wrote:
> >> I have had good results with mine once I shielded it from the  light. I 
> >> found
> >> that even indirect sunlight on a bright sunny day -- even inside a 
> >> radiation
> >> shield -- would cause the sensor to get all flaky. I put a small  piece 
> >> of
> >> black heat shrink tubing over it, leaving openings at each end for  the 
> >> air
> >> to circulate (i.e., I did not shrink the tubing, I just allowed it  to 
> >> remain
> >> loose). This sensor has been in place for about 18 months, and the 
> >> original
> >> one might have been OK too, if I had shielded it from the light.
> >
> >   The datasheets even state that the component is light sensitive.
> 
> Yes, however, I was surprised how light sensitive. IIRC, the data sheet said 
> avoid direct sunlight, but mine was affected by indirect sunlight. I'm just 
> saying, if your sensor is flaky, make it *really* dark. 

While proper shielding from light is good, I still think they're flaky
in the dark.  I've lost sensors both in summer and winter.  The sun do
rise throughout the winter here, but it's cloudy most of the time and
quite often my solar sensor only reaches 3-5 W/m² at noon and
automatic street lights are still on, and if that amount of daylight
is still a problem, the Honeywell sensor really is a problem.

I have my sensors in Davis radiation shields.  They seem to prevent
solar heating well, and should offer some light protection, but
they're too small to keep droplets away.  I've opened the Davis
shields in foggy and drizzly conditions a few times and my AAG sensors
have been soaky wet all over.

A few months ago I installed a humidity sensor for my father and he
had built a pretty large pagoda for it (the size of a small doghouse),
just like the old ones used by professional observers.  So far the
sensor has been working better than mine.  That is, not only is it
still working, but it also seem to saturate less in high humidity.
The use of a big pagoda seems promising.  The sensors in it don't
easily get wet.  Also, it probably has much less condensation issues.
Much like the "carport effect".  The cars in the street have a layer
of dew or frost in the morning after a clear night, but a small roof
just large enough to cover the car will leave it frost and dew free.

-- 
Steinar ; NIL DIFFICILE VOLENTI ; http://latinitas.org ; http://voksenlia.net