[wxqc] Sensor drift

[spamfree]

Hi,

It will. The Vantage Pro console measures the actual pressure (sensor pressure) internally, but calculates a sea level reduced pressure value which is what is displayed on the console, and passed on to connected weather programs. Their algorithm uses elevation as well as temperature and humidity in their calculation. The problem is that CWOP only wants altimeter for the pressure which is calculated from the sensor pressure and elevation only. The result is that if you are above around 500 ft elevation, your CWOP submitted pressure will appear to drift when compared to other non-vantage pro stations as the average temperature and humidity change. This is especially noticable after passage of a front and as the seasons change. 

I wrote a freeware tool to address this called VPLive http://www.pensom.org/weather/vptools/vplive.html . VPLive reverses the VP barometer calculation to get the sensor pressure, and then calculates the altimeter from that and sends that to APRS/CWOP.

You can also play around with the whole pressure calculation issue with this other freeware tool http://www.pensom.org/weather/vptools/vppressurecalc.html 

Steve
  
======= At 2006-05-22, 10:12:44 you wrote: =======

>I am experiencing what I believe to be sensor drift on the barometric 
>pressure sensor.  I've been following the diffs between my station and 
>KDNL / KAGS now for about two weeks, and altho a good portion of the 
>time, we are within 0.2mb of each other, last night, I was showing about 
>1.5mb or better between the two, with my reading being the higher.  The 
>only fly in the ointment is the fact that KHQU, Thomson GA, ASOS was 
>showing yet a higher reading than I was, by another 0.20 mb.  I know I 
>should not try to match most readings based on graphs, but baro pressure 
>I'd think should be very close, given our very similar altitudes. 
>
>In short, does anyone have any first hand knowledge or even theory that 
>the Davis baro sensor will, in fact, drift with change of temperature, 
>or time?
>
>Regards,
>
>Sam
>
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