[Hai-users] Temperature & Humidity sensor (fwd)

[Mike Nolan]

> Looks like an uphill battle given the tool we have to work with (PC
> Access!!!). I take it nobody has any creative code they wish to share that
> deals with this issue (and overcomes HAI's programming limitations)?

I think using the webtool that Thunder Scientific has online you could build
a reasonable set of tables and plug them into Access.  (Don't forget
that barometric pressure is the third variable in computing enthalphy 
along with temperature and relative humidity, if you're out for real 
precision.)

I gave up on trying to use home automation in my three-furnace unit 
seven-zone house two years ago and installed seven Honeywell programmable 
thermostats.  They do let me adjust the relative humidity at each unit 
rather than with a dial on the return duct.  

Most of the heating season savings in our house comes from passive solar 
heating, even when it's below 30 degrees outside the front part of the 
house can get up into the mid 70's on a sunny day.  (My basement office, 
below grade with no windows and with several computers on most of the time, 
is seldom cooler than about 76 in the wintertime.)
--
Mike Nolan

> 
> Paul 
> 
> -----Original Message-----
> From: hai-users-bounces at tssi.com [mailto:hai-users-bounces at tssi.com] On
> Behalf Of Mike Nolan
> Sent: November 1, 2005 10:09 PM
> To: hai-users at romaine.tssi.com
> Subject: Re: [Hai-users] Temperature & Humidity sensor (fwd)
> 
> > If anyone has access to an ASHRAE book the enthalpy chart is in there. 
> > It's not a simple algorithm. If you see the chart you'll know why, 
> > nothing linear about it. However, since memory is cheap these days and 
> > with some constraints on the input variables (limit the temperature 
> > and humidity inputs to reasonable values) you could probably come up with
> a lookup table.
> > Would take some time but you'd only have to do it once.
> 
> I haven't done thermodynamic calculations since I was an undergrad at
> Northwestern.  :-)
> 
> I don't have the book, here's a paper that includes an enthalpy graph. 
> It should be possible to pull several values directly off the table and
> interpolate enough to build a simple table.
> 
> http://ohioline.osu.edu/aex-fact/0120.html
> 
> And here's a site that you can download a humidity calculation app from.
> You will need IE with Active-X enabled:
> http://www.thunderscientific.com/web_humicalc/index.php
> --
> Mike Nolan
> 
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