Be sure to read https://github.com/weewx/weewx/wiki/Barometer,-pressure,-and-altimeter
Perhaps not a help, but Weatherflow has the calculations they use documented https://weatherflow.github.io/Tempest/api/derived-metric-formulas.html A while back I did the sea-level pressure calculation using the WF formula and it did match up with the offset I saw between a Weatherflow station and a VP2 for my low (365') elevation. There's some code at https://github.com/vinceskahan/weatherflow-calc-checker if you wanted to take a look there for some code to punch some numbers into (my example - I found the WF gear had a constant offset from the VP2 gear, so it was clear that one station was reporting data corrected to sealevel and one wasn't) On Saturday, January 7, 2023 at 9:38:45 PM UTC-8 Jeff A. D. wrote: > Did you get expected altimeter readings with wview? I don't know about > TWI, but I know the original Davis VP adjusted barometer that uses > temperature correction renders meaningless (to me at least) values at over > 7000ft, but then the >41" you're seeing is also meaningless to me. > > On my VP console I have an offset added of close to 7" to get a reasonable > reading on the console, then I have my weewx config file set up as: > > [StdCalibrate] > > [[Corrections]] > # For each type, an arbitrary calibration expression can be given. > # It should be in the units defined in the StdConvert section. > # Example: > foo = foo + 0.2 > barometer = 1.298 * barometer - 8.918558 > altimeter = barometer > pressure = barometer * 0.766377 > > The idea being that the station pressure, and also each change in > pressure, is approx. .298 less than SLP. If my math is correct your > pressure would need to be adjusted closer to .35. Assuming you don't use > an offset you could just set "barometer = 1.35 * barometer", or if you do > use an offset of 8" it would be something like "barometer = 1.35 * > barometer - 10.90" or "barometer = 1.35 * (barometer - 8)". > > Maybe someone else can give a better solution or correct my calculations, > but at least I seem to get more reasonable readings. > > > On Saturday, January 7, 2023 at 2:25:28 PM UTC-7 pannetron wrote: > >> Newbie here, coming from wview, and using a Texas Weather Instruments >> station. I've adjusted my console to display -- and report via its serial >> port -- an "altimeter" version of my barometric pressure so I can most >> easily compare my readings with other stations. Using the default weewx >> configuration, it must assume the reported pressure is gauge pressure since >> the calculated altimeter reading is up over 41"! At my home's altitude of >> 8258', my gauge pressure is around 22.15". It seems that I have two >> options for configuring weewx to see my correct barometric pressure. One >> is to set the >> [StdWXCalculate] like this: >> >> [[Calculations]] >> >> pressure = software >> altimeter = hardware >> barometer = software >> >> My other option to let weewx assume the pressure my station reports is >> gauge pressure and apply a correction offset of approximately -8". Which >> option is the preferred method? >> >> One final question. Since my barometric pressure sensor is indoors in >> the console, should the temperature used for corrections be indoor or >> outdoor temperature? >> >> Thanks, Russ. >> > -- 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/539522bd-e927-4554-8d2e-27817e65e2e9n%40googlegroups.com.
