I've left my local twi.py reporting what the station reports as "barometer". I'm pretty sure the station actually reports a calculated "altimeter" from its pressure sensor. To review, I calibrated my console to display local pressure adjusted to my altitude. If I let the driver report values as "pressure" weewx reports crazy high calculated values for barometer and altimeter. When I change the twi.py -- or the simulator -- to report only "altimeter", I get nothing in the barometer and pressure archive records. My weewx.conf is configure to expect "altimeter" from hardware and both barometer and pressure from software. Where should I look to see why weewx is not calculating barometer and pressure from altimeter? I'm fluent in python. I'd prefer this approach to configuring the twi.py driver to insert the stations readings into "pressure" and then having to put a large negative offset in weewx,conf to "correct" the pressure value. Does the calculation of barometer and pressure from altimeter require some time span of altimeter values?
On Monday, January 9, 2023 at 3:21:50 PM UTC-7 Jeff A. D. wrote: > Barometer uses outdoor temperature for correction. Indoor pressure for > all practical purposes is the same as outdoor pressure which is determined > by the weather. > > But again, if the algorithm is the same as for the original VP, then the > barometer corrections depending on temperature at high altitude are pretty > meaningless, at least to me. Maybe you would get better readings using a > more consistent indoor reading, but that's not the way it's meant to work > and wouldn't give true barometer readings, for whatever they're worth. > Altimeter is far more meaningful in my opinion, and seems to be what > stations around here use. > > On Monday, January 9, 2023 at 2:44:36 PM UTC-7 pannetron wrote: > >> 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 <tke...@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 <pann...@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+...@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+...@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. 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