[wxqc] CWOP Information for CW4490 (C4490) in Leander, TX US

[Victor Engel]

OK. But I thought the latest version of Weatherlink was sending altimeter --
and VWS as well. Do I have a wrong understanding there?

Victor

On Sun, Jun 1, 2008 at 12:37 PM, Ted Lum <gladstonefamily.net at tedworld.com>
wrote:

>  You might want to re-check this thread.
>
> http://server.gladstonefamily.net/pipermail/wxqc/2005-November/003212.html
>
>
> Sam Drinkard wrote:
>
> Victor Engel wrote:
>
>
>  I'm going to answer your question specifically and then also raise a
> more generic question.
>
> First, it looks like your pressure reading is too low. I believe if
> your mean error exceeds 2 millibars, you will get the message. When I
> first set up my stations (C6155) in 2006, I noticed it tracked another
> stations AS425 very closely in all data points, including pressure.
> Although we tracked closely, the analysis stated our readings were too
> low, so I made an adjustment upwards. My stations has had good QC for
> pressure ever since.
>
> I wonder, though, about something. All three of us use Davis Vantage
> Pro hardware, and all three of us were too low by similar amounts. Do
> these stations generally ship with a slight adjustment error? Could
> there be an adjustment needed at the factory? Certainly, we can't
> determine this from just three data points. I'm curious of others'
> experiences around the country, though, with this hardware.
>
> An alternative, of course, is that our hardware is correct and the
> analysis is wrong. Were that to be the case, though, the airport would
> be too high. I think that's unlikely, since aircraft rely on accurate
> altimeter readings to navigate.
>
> The other thing I've noticed but haven't spent time to check is that
> it appears the error in my readings may be correlated to temperature
> -- the higher the temperature the lower my reading with respect to the
> analysis. I may just be imagining that, and the magnitude of the
> effect certainly isn't large, if present. If this really is true,
> though, I wonder what would cause it.
>
> Victor C6155
>
>
>
>      Victor,
>
>     I've noticed the same thing with my station, which is a Davis
> WM-II.  If I look at the long term analysis of pressure, I can see a
> trend in the summer months that *seems* to degrade the sensor, but like
> you, I've not investigated this aspect.  As most of us know, nearly all
> electronic components have some variant or change with changes in the
> component's temperature.  Perhaps it would be a starting point to
> contact Davis and ask if there is any compensation built into the
> pressure sensor, or if ambient air temp changes would in fact, cause the
> sensor to not read in a non-linear fashion.
>
> Sam
>
>
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