weewx shows pressure value on index.html that looks like the barometer value at sealevel

[Alex Z99]

I deploy the weewx version 5.1.0 an station ist WS2816 (Technoline).

Altitude is 360 m above sealevel. It is defined in the section [Station] in weewx.conf, but the difference between station value and displayed value at index.html of weewx is about 45 mBar.

For example: The pressure value from station is 1020 mBar, This value is also transfered via mqtt to my broker, but at the index page with version: Seasons 5.0.2

it appears 1064 mBar which seem to be the pressure at sealevel.

I tried to fix that issue with correction in the section [StdCalibrate], but that did not work.

It seem that weewx displays the calculated barometer value from the real pressure value from station.

I have no idea how to fix that issue, any idea?

br

Alex

[gjr80]

WeeWX knows of three 'pressures', you can read about them here. If WeeWX knows any one of the three it will calculate the other two. For this to work properly you need to know which of the three pressures your station emits and the emitted pressure needs to be fed to the corresponding pressure field in WeeWX. Ideally, station or gauge pressure should be used as it is the raw pressure from the sensor and has not had any corrections. If the wrong pressure is fed to the wrong WeeWX pressure field the WeeWX calculated pressures will be incorrect and no amount of StdCalibrate will correct it.

You have not described your system setup, eg what driver are you using? how is it configured - what is weewx.conf?

By default the Seasons skins displays pressures using the WeeWX barometer field. You can alter this if you want by editing the Seasons skin config file, skin.conf, and adjusting the various [DisplayOptions] config options (essentially replace occurrences of barometer with the pressure field of your choice). Note that if you don't get the pressure feed into WeeWX correct you will still likely see significant differences between WeeWX and your console no matter what pressure you select.

Gary

[Alex Z99]

Hi Gary,

I edited the file %SKIN_ROOT%/Seasons/skin.conf (see attachment), but no change in behaviour visible.

According to the weews.conf (see attachment), the used driver for the WS2816 is

driver = weewx.drivers.ws28xx.

I also added a sceenshot of the displayed values in the index.html page

br

Alex

[gszla...@gmail.com]

There are two sea level pressures. One is QNH (Altimeter setting) and the other is MSLP.

Although WeeWX calculates both sea level pressures, the one that is displayed on the default Seasons skin is MSLP.(Mean Sea Level Pressure). WeeWX displays MSLP as "Barometer". 

MSLP is indeed, calculated from your station pressure. and converts your station pressure to an equivalent pressure at sea level.

Therefore at 360 m elevation and station pressure of 1020, WeeWX appears to be calculating MSLP correctly of about 1064 hPa.(depending on outside temperatures). 

However, a MSLP = 1064 sounds like an unrealistically  high pressure . In reading your weather station manual, it lloks like you can manually set your relative pressure to a calibrated pressure source like a close-by airport < 25 km. .

If your current relative pressure does not match QNH or Altimeter setting, then your station pressure could be inaccurate. If it is out, set your relative pressure to be the same as the airport Altimeter setting or QNH then subtract the offset of 45 hPa (44.7) to calculate your station pressure (QFE).Unfortunately, I did not find the procedure to adjust your station pressure in the manual.

You will have to check the accuracy of your barometer and re-calibrate if necessary. I would recommend that you refer to the barometer wiki for more specific guidance regarding calibration.  Although the wiki is intended for Ecowitt weather stations, the same principles apply to all weather stations. Go to www.barometer-wiki.ca/barometer and see the Archive section for "fixed offset" weather stations..

Good luck and let us know how it goes...

[Alex Z99]

Thanks a lot for the information. Few days ago I made the changes in the skin.conf as Gary suggested, but first there was no change in the displayed value of weewx visible, although I restarted the weewx process. After a while the pressure is displayed correct now. In addition I adjusted the absolute pressure in the station accordung to the present values of a nearby weatherstation at the airport. So everything works fine.

Thank you also very much for your support.

br

Alex