A similar issue may have come up before:
https://github.com/matthewwall/weewx-interceptor/issues/28 >From your post it looks like It your station is mapping REL pressure to weewx baromin . What does the output of weewxd look like? I think you would want to re-map your ABS pressure (if you have one) to weewx "pressure" so weewx can perform it's magic and calculate a weewx mean sea level pressure called "barometer". The reported solution in the github issue was to remap baromin by editing interceptor.py with 'baromin': 'pressure', Still though, the relative offset should not be changing values on its own. It is a fixed value (one must calculate it) based on the barometer elevation above sea level. If it doesn't stay at any value (including zero), your relative pressure value will not be correct. Does your Live data panel indicate a fluctuating relative pressure value when the relative pressure offset is changing on its own? Something is not right. You might want to do a factory reset (record the rainfall values and any other values you want to keep) or install/reinstall the latest firmware for your receiver. While we're at it - change the batteries on the T/H/P transmitter. If absolute pressure offset= 0 and relative pressure offset = 0 then, absolute pressure = relative pressure (Live data) = pressure value on the T/H/P transmitter And if you had to, you might be able to put the relative pressure offset (for your specific elevation) into weewx.conf as a calibration offset. However, try the reset and/or firmware download and see if that helps. Also, as a final resort, does your manufacturer offer any support? PS. I do not use interceptor.py, but about 5 years ago I did have a hardware "interceptor" device called the ATMOCOM (now long gone). In looking back at a data capture from 2019, these are the pressure values that I had: absbaromin=28.92& baromin=29.58& In my case, baromin was the relative pressure of the station and absbaromin was (obviously) absolute pressure. My station does not employ offsets (different firmware) so you had to adjust these two values to build in the offsets. On Monday, November 11, 2024 at 12:59:18 PM UTC-5 Ashley Hinton wrote: > Thanks for your reply. > > The station is a weathersleuth professional, apologies I should have been > clearer. When I bought it I figured because of weewx I didn't need, or > want, an indoor screen. > > https://www.aercusinstruments.com/aercus-instruments-weathersleuth-professional-ip-weather-station-with-direct-real-time-internet-monitoring/ > > Setting the station: > Absolute pressure offset = 0 > Relative pressure offset = 0 > > The LCD screen in the barometer transmitter is showing the same value as > both absolute & relative pressure on the live data webpage. > > If I stop weewx and listen for the data on the relevant tcp/ip port this > is what the station sends: > > sudo nc -l 7890 > > GET > /weatherstation/updateweatherstation.php?ID=***&PASSWORD=***&tempf=53.6&humidity=76&dewptf=46.2&windchillf=53.6&winddir=31&windspeedmph=0.00&windgustmph=0.00&rainin=0.00&dailyrainin=0.00&weeklyrainin=0.00&monthlyrainin=0.00&yearlyrainin=29.46&solarradiation=110.48&UV=0&indoortempf=67.3&indoorhumidity=61 > *&baromin=30.59*&dateutc=now&softwaretype=WH2600%20V2.2.8&action=updateraw&realtime=1&rtfreq=5 > > HTTP/1.0 > > The *baromin* value is the relative pressure. It doesn't send any other > pressure values. > > If I offset in hardware it works and weewx reports barometer correctly > compared to local reliable sources but it doesn't (always!) survive a power > outage. Whats worse is the relative offset doesn't even stay defaulted to 0 > - give it a few minutes and it does its own thing, literally a random minus > value based on no other setting I can find, unless I manually change the > offset value again but it only stays until it loses power. > > My thoughts were to map *baromin *(relative pressure) from the station to > *pressure > *in weewx, leave the station relative pressure offset at zero and let > weewx calculate barometer as you suggest, of course double checking the > altitude value in weewx.conf is correct. Now I know it won't work after a > power cut, and I suspect even if I manually set zero offset and kill the > power it will initially return with zero and then change to a random value. > > Station firmware is up to date - v2.2.8 is the last available. > > However I'm starting to think I could get the pressure reading from > elsewhere. I'm running an Arduino in the greenhouse which is providing some > extra sensor data picked up by weewx using the Weewx MQTT Subscribe > extension. > > Adding a barometric sensor to the Arduino should be pretty easy, mapping > its output to *pressure *in weewx. > > Either that or read the station live data webpage into weewx but it seems > a lot of hassle compared to a buying a relatively cheap sensor. The one > I've just looked at claims an accuracy of 0.01mbar. > > Maybe that's the solution - map an incoming MQTT topic > "greenhouse/absolutepressure" to pressure in weewx. > > [[[greenhouse/absolutepressure]]] #mqtt topic sent from Arduino > > name = pressure #weewx database table > > > .. and under > > [[Calculations]] > > > Change *prefer_hardware* in the following entries to: > > pressure = hardware > > altimeter = software > > barometer = software > > Which I think would ignore the station relative pressure (barometer) and > since its not sending absolute pressure anyway I need not worry about a > conflict between the station and what the Arduino would be sending. > > Also apologies again, I should have mentioned in my original post: > > Weewx v5.1.0 (installed via pip/venv) > Raspberry Pi 4 > Raspian (Debian) v12 Bookworm (arm64) > Aercus Instruments Weathersleuth Professional station. > > > On Friday 25 October 2024 at 12:03:49 UTC+1 [email protected] wrote: > > --Hmm..if Absolute pressure and relative pressure = 0 (zero) your > barometer was not set up correctly and not calibrated correctly. II > absolute pressure = 0, you would be living in a vacuum! Or are you > referring to both offsets = 0? > > Your station is the weathersleuth IP? If so, you have an outside array, a > Wi-Fi gateway and a separate LCD indoor sensor with a barometer sensor: > Thermo-hygrometer-barometer transmitter (temperature/humidity/pressure). > > If your barometer is working, it should be reading the current atmospheric > pressure at your elevation (the elevation of your barometer). In your > calibration screen, you should see an absolute pressure offset and a > relative pressure offset. These fields are used to adjust your absolute > pressure and relative pressure, respectively. > > It is best to start over from scratch. Set both offsets back to zero in > the calibration screen. Verify that the pressure showing on the LCD screen > of the external Thermo-hygrometer-barometer transmitter is equal to the > absolute pressure on your console. Maybe it's under the Live data tab? > > You will have to calculate your relative pressure offset which depends on > your elevation. > Your weather station appears to be similar to an Ecowitt or Ambient > weather station therefore calibration procedures should be the same. Read > the barometer wiki to set your elevation and calibrate your barometer: > > http://meshka.eu/Ecowitt/dokuwiki/doku.php?id=barometer#calibration_wi-fi_gateways > > Your other question relates to WeeWX. You definitely do not want to pass > on your weather station's REL to WeeWX. Your weather station uses a single > fixed offset amount to do an estimate of sea level pressure. It can be a > reasonably close approximation but your readings will drift at times. You > would be far better off relying on WeeWX "barometer" pressure reading > because it uses an actual algorithm to calculate sea level pressure much > more accurately. To obtain the WeewX "barometer" reading you do not need to > configure anything. WeeWX will automatically calculate "barometer" from > your absolute pressure. BTW, the WeeWX "barometer" reading refers to SLP > (sea level pressure) that you might see on meteorological isobar > charts/surface analysis maps. If you follow the wiki's tutorials, your REL > (relative pressure) on your station's console should be an approximation of > the Altimeter setting. > > On Tuesday, October 22, 2024 at 4:43:24 AM UTC-4 Ashley Hinton wrote: > > Hi Michael > > Thanks for your reply. > > I did indeed read it which made me realise the issue is what WeeWx is > receiving (in relation to what its displaying on the webpage) & that it > needs to be calibrated somewhere. > I will first calibrate the hardware & then check what value from the > hardware is being displayed on the webpage. I'm pretty certain at the > moment Relative Pressure from hardware = Barometer on the webpage but will > double check so I know in future. > > Thanks again, > > On Monday 21 October 2024 at 04:56:31 UTC+1 [email protected] wrote: > > Hello, as a first step, did you read the following: > https://weewx.com/docs/5.1/usersguide/troubleshooting/meteo/ > > After that, do you know the pressure mappings console <=> weewx? Then, > which of the values (pressure, altimeter, barometer) is displayed on the > webpage? If you know all these things, calibrate your hardware according to > the manual and choose your desired obs_type to be displayed on the webpage. > > > Ashley Hinton schrieb am Sonntag, 20. Oktober 2024 um 22:08:57 UTC+2: > > Hello > > I've noticed my Barometer reading is different from other local sources: > the airfield just up the road from me, the local weather report, my phone > weather app - you name it, my readings did not agree. WeeWx was reporting > too high. > > I'm using an Aercus IP weather station and WeeWx is using the Interceptor > driver. > The weather station itself has its own calibration settings page, it has > two fields for calibrating pressure: > > Absolute Pressure (was, and is, set to 0) > Relative Pressure (was set to 30.00hpa which I'm sure was arbitrary, now > set to 0) > > If I change the Relative Pressure offset the Barometer value reported on > the resulting WeeWx-generated webpage changes, so I'm confident that > Relative Pressure is what's sent to WeeWx. > > My question is what to do - calculate and set the calibration in hardware, > or in WeeWx? What is generally preferred or considered the best option? > > Thanks! > > -- 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]. 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