[Weather] termperature offset on Dalsemi station

[Ernie Oporto]

I forgot to mention that the internal sensor temp is actually 7-10 degrees
LOWER than the real temp.
But I can guess that because the thing is in the shade it keeps the cool air
inside from the night before and never heats up.  I made a pagoda a few
years ago for the humidity sensor out of a lawn lamp, so I'll just do the
same for this.

Does anyone recommend AGAINST using the Trh sensor for temp?  I seem to
recall that had issues too.



On 3/30/07, Rich Mulvey <weather at mulveyfamily.com> wrote:
>
> Ernie Oporto wrote:
> >
> > You can see at the link below that my Dalsemi station seems to send
> > data that is 7-10 degrees off from other stations around me.  Most of
> > the time this is because my station is in the shade due to my condo
> > complex's rules about where I can mount things.  Of course, at night,
> > we are all in the shade and the temperature difference is still
> > there.  This is one of the original dalsemi 1-wire stations.
> >
> > http://www.findu.com/cgi-bin/wxnear.cgi?call=CW0861
> >
> > Surprisingly, the Trh in my humidity sensor (one of the original
> > humidity sensors that were sent out in samples) seems to show the
> > right temperature.  I'm sure I can fudge OWW to read the temp from the
> > humidity sensor for sending to findu.com <http://findu.com>, but I'd
> > like to see if I can get to the root of the problem and correct the
> > temp.  Is there any known issue I should be looking for that might
> > cause this?  Any recommendations?
> >
>
>
>    Is this the temperature sensor mounted in the DalSemi weather head?
>
>    If so - you're *never* going to be able to get a reliable, consistent
> reading from it.  The problem is that the sensor is mounted in a sealed
> enclosure, and thus is not measuring the air temperature - it will be
> offset based on the amount of sunlight, cloudiness, how much heat is
> being absorbed by the weather head, etc.  So you'll generally see the
> temps running high in the daytime, and low at night.  You can't just
> apply an offset to the temps, because there are so many variables that
> will affect the measurement.
>
>    The solution is to mount a completely separate temp sensor in a
> properly ventilated enclosure - google for "weather pagoda" or
> "stevenson screen" for many ideas in that regard.
>
> - Rich
>
>
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-- 
Ernie
http://www.shokk.com/blog/
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