[wxqc] Sensor drift

[spamfree]

Hi,

Are you comparing apples and oranges? Comparing the console's Sea Level Reduced pressure to an airport's altimeter value is not a proper comparison unless the elevations of the two stations are at or very near sea level. Since starting to use software that converts my VP2's pressure to altimeter (which is what I submit to CWOP), my station stays within 1 or 2 mb of the nearby ASOS airport station and I haven't calibrated my barometer in over 5 months.

Either your unit was defective, or you are at elevation and are comparing SLP to altimeter, which is an invalid comparison.

Steve
  
======= At 2006-05-23, 12:05:00 you wrote: =======

>The following are the specs direct from the Davis web site:
>
>4, Wireless Vantage Pro® & Vantage Pro Plus™ Stations
>VANTAGE PRO
>Barometric Pressure (sensor located in console)
>Resolution and Units . . . . . . . . . . . . . . . . . . . . . 0.01" Hg, 0.1 mm Hg, 0.1 hPa/mb (user-selectable)
>Corrected Range . . . . . . . . . . . . . . . . . . . . . . . 26.00" to 32.00" Hg, 660.0 to 810.0 mm Hg, 880.0 to 1080.0 hPa/mb
>Uncorrected Range. . . . . . . . . . . . . . . . . . . . . . 18.00" to 33.50" Hg, 457.0 to 850.0 mm Hg, 592.0 to 1130.0 hPa/mb
>Elevation Range . . . . . . . . . . . . . . . . . . . . . . . . -999’ to +12,500’ (-305 m to 3810 m)
>Uncorrected Reading Accuracy . . . . . . . . . . . . . ±0.03" Hg (±0.8 mm Hg, ±1.0 hPa/mb) (at room temperature)
>Sea-Level Reduction Equation Used . . . . . . . . . United States Method employed prior to use of current "R Factor" method
>Equation Source . . . . . . . . . . . . . . . . . . . . . . . . Smithsonian Meteorological Tables
>Equation Accuracy . . . . . . . . . . . . . . . . . . . . . . ±0.01" Hg (±0.3 mm Hg, ±0.3 hPa/mb)
>Elevation Accuracy Required . . . . . . . . . . . . . . ±10’ (3m) to meet equation accuracy specification
>Overall Accuracy. . . . . . . . . . . . . . . . . . . . . . . . ±0.04" Hg (±1.0 mm Hg, ±1.4 hPa/mb)
>Trend (change in 3 hours) . . . . . . . . . . . . . . . . . Change Š0.6" (2 hPa/mb, 1.5 mm Hg) = Rapidly
>Change Š0.2" (.7hPa/mb, .5 mm Hg)= Slowly
>Trend Indication . . . . . . . . . . . . . . . . . . . . . . . . 5 position arrow: Rising (rapidly or slowly), Steady, or Falling (rapidly or
>slowly)
>Update Interval . . . . . . . . . . . . . . . . . . . . . . . . . 15 minutes or when console BAR key is pressed twice
>Current Data . . . . . . . . . . . . . . . . . . . . . . . . . . . Instant, 15-min., and Hourly Reading; Daily, Monthly, High and Low
>Historical Data . . . . . . . . . . . . . . . . . . . . . . . . . 15-min. and Hourly Reading; Daily, Monthly Highs and Lows
>Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High Threshold from Current Trend for Storm Clearing (Rising Trend
>Low Threshold from Current Trend for Storm Warning (Falling Trend)
>Range for Rising and Falling Trend Alarms . . . . 0.01 to 0.25" Hg (0.1 to 6.4 mm Hg, 0.1 to 8.5 hPa/mb )
>
>I just sent in a 30 day old console from a Vantage II Plus for the barometer moving over 5 to 10MB in a 24 hr time period after being set from a local standard known to be accurate. It is an automated station set up at a local airport by the FAA and NWS Ckeched regurly by them to be accurate to use for interment flying.  If I relied on the Davis it would have me screwed in the ground the way it goes all over the range.  This unit was not stable at all and did not even meet the specs!!!!
>
>N5IHE
>
>