Good catch. No, the station has no input for altitude. And I was wrong about setting the tags in twi.py to "altitude" -- that caused issues with the Belchertown skin I use and the value reported to PWSWeather. I changed the tags to "barometer" and things work okay now but I'm left unsure what errors that may introduce into calculated station pressure and altitude pressure values. That's something I can live with. Seems only a few folks use a TWI station so maybe this is good enough as long as the hack is made known as a caveat?
I suspect the station displays and reports "gauge pressure." I manually adjusted the station's barometer calibration for my altitude so the console display is meaningful for comparisons with other stations around me and agrees with my Kestrel 3000. The values reported to CWOP compare very well with neighboring stations. Some day I may play with setting the tags in twi.py back to "pressure" and, as others suggested, use a calibration calculation in weewx.conf to get back to true "gauge pressure". One of my questions remains unanswered: since the barometric sensor is indoors, should SLP adjustments for temperature use indoor or outdoor temperature? BTW, Tom, thanks so much for your replies and work on weeWX!!! Russ On Mon, Jan 9, 2023 at 12:55 PM Tom Keffer <tkef...@gmail.com> wrote: > Sounds good. > > Just a reality check: if your instrument emits altimeter pressure, then > there must be a way of setting altitude in the instrument. Hope that's true. > > On Mon, Jan 9, 2023 at 7:23 AM pannetron <pannet...@gmail.com> wrote: > >> Update on a revised twi.py. Changing the genLoopPacket "tags" from >> "pressure" to "altimeter" from values parsed from the station reports did >> the trick. After some previous changes from strings to binary strings, >> there was a bug with how wind_dir values were parsed so I fixed that, too. >> After a few more days of testing, I'll submit a PR. >> >> On Sunday, January 8, 2023 at 10:45:43 AM UTC-7 pannetron wrote: >> >>> On Sun, Jan 8, 2023 at 4:51 AM Tom Keffer <tke...@gmail.com> wrote: >>> >>>> It sounds like the TWI instrument is emitting "altimeter" or >>>> "barometer", but the driver is labelling it "pressure" (i.e., gauge >>>> pressure). So, weewx feels the need to "correct" it to SLP, resulting in >>>> your enormous pressures. >>>> >>>> I would recommend filing an issue at the TWI repository >>>> <https://github.com/matthewwall/weewx-twi>. Expect it to take a while. >>>> Matthew is swamped. >>>> >>>> Or, better yet, do a fork and submit a PR. >>>> >>>> Cloned weewx-twi, working on a revised driver. The current driver is >>> populating loop packets with "pressure" while the station reports >>> "altitude"... >>> >> -- >> 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 weewx-user+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/98794c13-7fe5-4475-b164-439a4c2e08a4n%40googlegroups.com >> <https://groups.google.com/d/msgid/weewx-user/98794c13-7fe5-4475-b164-439a4c2e08a4n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to a topic in the > Google Groups "weewx-user" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/weewx-user/pwYg9Ywilfw/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > weewx-user+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-user/CAPq0zEDJvgZSYothF5%3D8_6RH63CE0YZuek-GBDdsEL052vuf%3Dg%40mail.gmail.com > <https://groups.google.com/d/msgid/weewx-user/CAPq0zEDJvgZSYothF5%3D8_6RH63CE0YZuek-GBDdsEL052vuf%3Dg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- 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 weewx-user+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/CADDHxw6nV3-2PfPgfc-FKc%2BQy%2B082a%2BdG35j5svG5j2QRuT3RA%40mail.gmail.com.
