Belchertown Skin and CWOP Pressure Difference

[Chris Plant]

Hello, 

Just wondering if someone could clue me in as to why the Belchertown skin is showing my barometer .03 more inHg than the data thats being uploaded to CWOP and other providers. When i change my skin to the "Standard", they then match.  Is it something in the programming or are they values not really the same thing?

Chris

https://www.knowltonweather.com

[kutz...@gmail.com]

So the Belchertown skin is showing the MQTT return, which is the latest LOOP value. I could be wrong, but I suspect the Standard skin, and the upload to CWOP are values from the last archive value stored in weewx.sdb.

phil

[Chris Plant]

Hmmm.  Ok. I’ll have to try it with the MQTT off and see if they are the same or different. 

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Chris Plant
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[Chris Plant]

I turned off the MQTT and it’s still showing different. Any thoughts?

On Thu, Mar 28, 2019 at 4:42 PM <kutz...@gmail.com> wrote:

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[kutz...@gmail.com]

I see that you upload to several other services (PWS, WU and Weathercloud). Are they getting the same barometer values as CWOP?

I would also look at the weewx.sdb database with sqlite3 to see what the actual archived value is at a particular time (like 8pm tonight) and compare it to the values on the Belchertown skin and on the various external services you've uploaded to.

Is there some offset you've applied to the barometric pressure on your Accurite?

For what it is worth, my upload to CWOP gives a barometric pressure reading within .01 inHg of what my Belchertown skin shows (https://wx.kutzenco.com). I attribute the difference to conversion. I think CWOP stores data as millibar and the findU display converts that to inHg (I may be wrong).

phil

[Chris Plant]

Well I’ll be. It appears CWOP is the only one that’s different. The Belchertown skin amount is the same as PwsWeather and Weathercloud. So it must be something with how CWOP calculates it as you mentioned. Well thanks for helping me with this at least.

[gjr80]

Hi.

Make sure you are comparing apples with apples and not oranges. The CWOP uploader uploads WeeWX field altimeter in mbar (WeeWX does the conversion/rounding to mbar not CWOP). The PWS uploader uploads WeeWX field barometer. I can't access the WeatherCloud uploader at the moment but I am suspecting it will be uploading barometer as well. I haven't looked at Belchertown but I am guessing it will likely be barometer. What any of these external services do with the 'pressure' value that is uploaded is anyone's guess so even the fact you are uploading different values is no guarantee of what they display.

If you want to see what is being uploaded to CWOP and PWS set debug=2 in weewx.conf then restart WeeWX, you should the data being uploaded in the log. Can't speak for WeatherCloud but debug=2 may well cause it's data to be logged as well.

Gary

[Chris Plant]

Ah thanks Gary. That’s exactly what I’m trying to do. Make sure I’m looking at everything I’m supposed to. Thanks for the suggestion! 

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