On Saturday, November 21, 2020 at 9:31:11 AM UTC-8 [email protected] wrote:

> [email protected] schrieb am Samstag, 21. November 2020 um 16:09:22 
> UTC+1:
>
>> Ooops, after 10 mn the 2 values have diverged (only 1 mbar)
>> The explanation is that weatherlinkliveudp driver uses "altimeter" and 
>> WLLDriver uses "barometer" for the station info
>>
>
> That I do not understand. Does the driver only retrieves the readings from 
> the hardware, doesn't it? So, which way the driver can influence which 
> values is displayed?
>  
>

There are two pressure-related elements provided by the Davis hardware.   
 One is the pressure as reported by the sensor, the other is the pressure 
corrected to sea-level pressure based on your altitude.    The driver code 
defines which sensor values it uses for what generic weewx database element

Both drivers map 'bar_absolute' from the hardware to weewx 'pressure' in 
the database.

But...the two drivers map 'bar_sea_level' from the hardware to different 
elements in weewx's database.

   - WLLDriver.py           puts the value into 'barometer' in weewx
   - weatherlinkliveudp.py  puts the value into 'altimeter' in weewx

According to 
https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter, the 
correction math differs slightly, so I'd expect slight differences perhaps. 
 A difference of 1 mbar to me isn't something to worry too much.  You're 
talking 0.1 percent offset.  The sensor itself isn't that precise to begin 
with.


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