[wxqc] Barometer corrections

[webmaster]

Hello Steve,

I will take your word for what is reported as I don't know off 
hand.  What I do know is that the local AWOS reports the same thing 
that my Davis does and they don't seem to go up and down 
together.  Their barometer seems to track with the MADIS analysis 
well enough to get two thumbs up and my unit doesn't.  So from time 
to time I call their automated phone service and get their reading 
and change my barometer to match theirs.

I have weatherlink software but I don't use it.  I use Weather 
Display.  I checked in the CWOP setup section and see there is a 
section entitled "VP altimeter setup".

There is a box that says "Send altimeter pressure {Davis VP station}"

And if you check that box, you then get another box option "Use this 
pressure for WD baro reading"

How would I know which of these boxes to check and why?

If I switch from sending one vs. the other, will CWOP know?

I am ignorant enough not to know one from the other and how they 
differ and which one I want to use.  I thought I was already using 
the "altimeter" value as the AWOS says the their "altimeter" value is 
X and in fact I just called and we had exactly the same value.  I 
know CWOP shows in millibars, but my Davis display and my WD display 
both show "altimeter" value as far as I know?  Right now KLVN and my 
station both say 29.64.

I noticed that when I last added more precip manually to WD that 
somehow my temperature got accidentally offset by 10 or so degrees so 
I have a nasty error in my data for about 6 hours.  That is the 
second time now when changing one value in WD that another value got 
changed even though I didn't change the other field...bizarre.

Thanks so much!

Lew

>Date: Fri, 11 Apr 2008 01:10:24 -0600
>From: "Steve" <steve at softwx.com>
>Subject: Re: [wxqc] Vantage Pro Barometer problems
>
>
>The problem had to do with the fact that the Vantage Pro station reports Sea
>Level Pressure (SLP) but CWOP wants altimeter for the the pressure. The two
>values are not the same, and the difference between them increases with the
>elevation of your station location. However, that should no longer be an
>issue if people are using the latest version of WeatherLink. Davis recently
>made a change so that WeatherLink calculates the proper altimeter value and
>sends that to CWOP. Several other software programs that connect to the
>Vantage Pro also will correctly calculate and send the alitimeter value,
>although you may need to enable that feature in the configuration screen.
>So, for most people, there should no longer be any need to do goofy
>workarounds for the VP pressure to get good data to CWOP.
>
>Steve
>SoftWx



******************************************
Lew - Amateur Weatherman
lew at farmingtonweather.com
Farmington Weather
www.farmingtonweather.com
Farmington, Minnesota, USA