Thank you for your precious answers and for the historical insight, always useful to get the reason behind a choice
Il giorno domenica 17 luglio 2022 alle 19:53:31 UTC+2 [email protected] ha scritto: > Greg has it exactly right. > > Until the introduction of LOOP2 packets about 8 or 9 years ago, the > Vantage stations behaved this way. They only published pressure reduced to > sea-level (SLP), so station pressure (and altimeter pressure) had to be > back calculated. > > -tk > > On Sun, Jul 17, 2022 at 7:56 AM Greg Troxel <[email protected]> wrote: > >> >> Andrea Di Saverio <[email protected]> writes: >> >> > If, as stated >> > here >> https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter, >> > the `pressure` is the raw value measured by the station, why is it in >> the >> > `Calculations` section in the configuration file >> > (https://www.weewx.com/docs/usersguide.htm#[[Calculations]])? >> > I expected it cannot be calculated, rather it is the starting point to >> > calculate the `altimeter` and `barometer` values. >> >> There is a long chain of processing. >> >> Somewhere in the weather station (you didn't say which one) there is a >> pressure sensor, and almost always these are measuring station pressure >> (with some offest that may require calibration). >> >> Then, various weather stations process that pressure to form barometric >> pressure or altimeter pressure, because that's what ~everybody wants to >> see. >> >> The weather station communicates some kind of pressure information to >> weewx, and that depends on at least the station type, and perhaps on how >> it is connected. >> >> weewx then does some combination of: >> - use values that are reported ("hardware" is the code word for this) >> - calculate values, in the case that >> * they are not reported >> * config, or defaults, say that's better than using the reported value >> >> The following behavior would not be surprising at all: >> >> station has station_pressure sensor >> >> station applies some reduction to barometric pressure >> >> station UI displays only barometric pressure >> >> station reports only barometric pressure to weewx >> >> weewx calculates station pressure by essentially inverting the >> station's reduction to barometric, using configured elevation and >> temperature >> >> weewx calculates altimeter pressure from station pressure and >> configured elevation >> >> >> See: >> https://www.weewx.com/docs/usersguide.htm#pressure_calibration >> >> -- >> You received this message because you are subscribed to the Google Groups >> "weewx-user" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/rmiilnvvldj.fsf%40s1.lexort.com >> . >> > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/7154cfcb-ecc9-4f11-8f5e-72d06a3baec7n%40googlegroups.com.
