As this thread has drawn on I agree the solution is in the driver. I found it had to believe that a driver could have been around for so long with an incorrect 'pressure' being used and the issue never having come up before. Sure enough, this thread <https://groups.google.com/d/topic/weewx-user/hFp03F9XVH4/discussion> from 2016 bears a remarkable similarity to the issue here. It also seems that Tom acknowledged that the WS2813 actually outputs altimeter not pressure as coded in the driver. Later in the thread there are suggested changes to the driver but it gets a bit murky around some corrections that are being applied within StdCaibrate. Seems no changes were ever made to the driver though. Might be worthwhile for Tom or Matthew to revisit this.
Gary On Saturday, 15 February 2020 14:22:07 UTC+10, ln77 wrote: > > OK… The “pressure” that your station is displaying is what it should be > displaying: the ambient air pressure, correct for your altitude. In weewx, > this is called “barometer” because that is what weather stations report for > barometric pressure. “Altimeter” is basically the same thing; there are > differences in exactly how it is corrected, but those differences are minor > and can be ignored for now. The distinction between what weewx calls > “barometer” and “pressure” is important, though, for anyone more than a few > hundred feet above sea level. > > From the manual, it appears that the WS-2813 uses a simple method for > correcting to sea level, by allowing the user to adjust a correction factor > that is applied to the actual measured pressure until the reading matches > some local reference barometric pressure report. This automatically also > corrects for any errors in the pressure sensor itself, a handy bonus. > There’s not reference in the manual to any other kind of pressure being > reported, so it only makes sense that what it transmits via the USB > interface is also this corrected pressure, i.e., “barometer.” But the > WS28XX driver documentation, and as far as I can tell the code also, assume > that the pressure reading fro the hardware is what weewx calls “pressure,” > that is, the actual ambient pressure before correction for altitude. As > far as I can tell, all of the WS28XX LaCrosse stations work the same way as > yours and actually send the corrected barometer reading. Maybe because the > LaCrosse documentation calls it “pressure,” it was mistakenly interpreted > as raw pressure reading in the driver. > > The bottom line is, I’m pretty sure the issue is that the driver is wrong. > I’m not familiar enough with that part of the weewx code to offer a fix, > but it should be pretty simple for someone who is familiar with that code. > > -Les > > > > On 14 Feb 2020, at 19:44, Dan Blanchard <[email protected] <javascript:>> > wrote: > > It is likely that I am mis-using the terms altimeter, barometer, and > pressure. I'll clarify what I mean here. > > What I previously defined as 'correct' pressure is that the pressure > reported by my station (LaCrosse WS-2813U-IT) matches the National Weather > Service barometer reading ( > https://forecast.weather.gov/MapClick.php?lat=47.715130000000045&lon=-116.94667999999996#.XkdkXDFKiUk). > > For example, *right now* my station is reading 30.06 pressure and the NWS > site is reporting 30.0 barometer. Ultimately I just want my WS-2813 > pressure reading to match the WU pressure reading ( > https://www.wunderground.com/dashboard/pws/KIDPOSTF43). Right now it > appears that WU is reading the weewx barometer reading. Is there a way to > have weewx report the pressure reading to WU? > > My WS-2813 outputs the manually adjusted pressure in the Loop records (see > attachment). I don't see a way to change that. Here is a link to the > manual ( > https://www.lacrossetechnology.com/media/catalog/product/w/s/ws-2813u-it.pdf > ). > > On Friday, February 14, 2020 at 9:22:17 AM UTC-8, Andrew Milner wrote: >> >> I would expect you to be reporting barometer = sea level pressure which >> is pressure adjusted for temperature and altitude because weather stations >> always report sea level pressures. >> >> Is what you call 'correct' pressure the raw pressure of the instrument or >> a pressure which you have set. Does the station output the raw pressure or >> the manually adjusted pressure in the loop records? >> >> >> >> On Friday, 14 February 2020 18:07:15 UTC+2, Dan Blanchard wrote: >>> >>> Andrew, that's a good questions; let me clarify. >>> >>> This issue started when Weather Underground (WU) stopped showing my >>> station on the maps. I found out that was because I was reporting an >>> incorrect barometric 'pressure.' As I dug into the details I found that my >>> *station >>> *was displaying the correct pressure (29.xx) but by the time it got to >>> WU, it was displaying the barometer reading (32.xx) from weewx. This can >>> also be demonstrated by looking at the data displayed at >>> /var/www/html/weewx/index.html >>> (see attachment) so I assume that weewx is taking the pressure from my >>> station and somehow converting it or exchanging it for barometric pressure >>> before it gets uploaded to WU. I just want the pressure from my unit to be >>> what is reported to WU. >>> >>> Side note: I've been running this station for many years on a Windows >>> based system and it has been working fine. So I know the hardware side is >>> working; just something different about how weewx reports pressure (or >>> barometer, or altimiter). >>> >>> Does that help clarify my issue? >>> >>> On Friday, February 14, 2020 at 2:24:31 AM UTC-8, Andrew Milner wrote: >>>> >>>> I am not sure I understand what you think is wrong with the readings of >>>> Pressure 29.89 >>>> Barometer 32.609 >>>> Altimeter 32.40 >>>> and why you believe something is wrong >>>> >>>> >>>> On Friday, 14 February 2020 05:57:36 UTC+2, Dan Blanchard wrote: >>>>> >>>>> Altitude is 2,320 ft. and the values are in the screen shot on the >>>>> previous post. Did you see that? >>>>> >>>>> On Thursday, February 13, 2020 at 7:16:11 PM UTC-8, Andrew Milner >>>>> wrote: >>>>>> >>>>>> I give up - looks correct to me. >>>>>> >>>>>> have you run from the command line and seen the LOOP and REC data >>>>>> weewx is receiving? >>>>>> >>>>>> what altitude is your station, and what values are you currently >>>>>> getting for pressure, barometer and altimeter? >>>>>> >>>>>> On Thursday, 13 February 2020 22:10:08 UTC+2, Dan Blanchard wrote: >>>>>>> >>>>>>> I don't know, but that makes sense so I did it. I'm still not >>>>>>> getting desired results though. >>>>>>> >>>>>>> On Thursday, February 13, 2020 at 9:38:55 AM UTC-8, Kevin Davis >>>>>>> wrote: >>>>>>>> >>>>>>>> Do you need a space between your minus sign and the adjustment >>>>>>>> value? >>>>>>>> >>>>>>>> On Thu, Feb 13, 2020 at 9:32 AM Dan Blanchard <[email protected]> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> Hey Andrew, will you please look at the attached screen shots and >>>>>>>>> let me know if this looks correct? >>>>>>>>> >>>>>>>>> Do I need to restart (sudo /etc/init.d/weewx restart) after I >>>>>>>>> make these changes? I have and the changes don't seem to be taking >>>>>>>>> effect. Is there something else I need to do? >>>>>>>>> >>>>>>>>> With regard to the barometer and altimeter having the same >>>>>>>>> settings; I have probably misled. They are not exactly the same but >>>>>>>>> they >>>>>>>>> were relatively close to each other compared to the pressure value. >>>>>>>>> Here >>>>>>>>> are the current readings as of now when I run sudo weewxd >>>>>>>>> /etc/weewx/weewx.conf. >>>>>>>>> >>>>>>>>> pressure: 29.98 >>>>>>>>> altimeter: 32.57 >>>>>>>>> barometer: 32.74 >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Thursday, February 13, 2020 at 12:07:50 AM UTC-8, Andrew Milner >>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>> If you have a LaCrosse WS28xx station then according to the >>>>>>>>>> hardware guide the station outputs PRESSURE in weewx terminology - >>>>>>>>>> regardless of what LaCrosse call it - and weewx should calculate >>>>>>>>>> barometer >>>>>>>>>> and altimeter settings. >>>>>>>>>> >>>>>>>>>> If pressure is incorrect then it can be adjusted as you specified >>>>>>>>>> - by adjusting pressure (not barometer or altimeter) >>>>>>>>>> >>>>>>>>>> Make sure pressure is set to use hardware and barometer and >>>>>>>>>> altimeter are set to use software. >>>>>>>>>> >>>>>>>>>> I am surprised barometer and altimeter are the same values - have >>>>>>>>>> you set the station's altitude in weewx.conf, and have you specified >>>>>>>>>> software generation for the values? >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Thursday, 13 February 2020 09:23:27 UTC+2, Dan Blanchard wrote: >>>>>>>>>>> >>>>>>>>>>> Andrew, are you suggesting that I make a 'correction' entry >>>>>>>>>>> under [StdCalibrate] such as barometer = barometer -2.8 assuming >>>>>>>>>>> that I am >>>>>>>>>>> getting a pressure reading of 30.13 and Barometer and ALtitude >>>>>>>>>>> readings of >>>>>>>>>>> 32.93? >>>>>>>>>>> >>>>>>>>>>> (see attached screenshot) >>>>>>>>>>> >>>>>>>>>>> On Wednesday, February 12, 2020 at 7:42:08 PM UTC-8, Andrew >>>>>>>>>>> Milner wrote: >>>>>>>>>>>> >>>>>>>>>>>> 1. use stdcalibrate section of weewx.conf >>>>>>>>>>>> http://weewx.com/docs/usersguide.htm#StdCalibrate >>>>>>>>>>>> 2. FO station = Fine Offset weather station >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> On Wednesday, 12 February 2020 22:15:48 UTC+2, Dan Blanchard >>>>>>>>>>>> wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> Andrew, how do I calibrate the pressure in weewx? Also, what's >>>>>>>>>>>>> a FO station? >>>>>>>>>>>>> >>>>>>>>>>>>> On Tuesday, February 11, 2020 at 8:01:08 PM UTC-8, Andrew >>>>>>>>>>>>> Milner wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>> check that the absolute pressure is correct - I have had a FO >>>>>>>>>>>>>> station which had a dodgy pressure sensor before now. >>>>>>>>>>>>>> Calibrating pressure >>>>>>>>>>>>>> in weewx solved it. >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>> -- >>>>>>>>> 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/08c79655-b1af-4134-9a2b-82a4f52f051f%40googlegroups.com >>>>>>>>> >>>>>>>>> <https://groups.google.com/d/msgid/weewx-user/08c79655-b1af-4134-9a2b-82a4f52f051f%40googlegroups.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 [email protected] <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-user/a24bec68-9459-43f4-8765-933c0c1f2490%40googlegroups.com > > <https://groups.google.com/d/msgid/weewx-user/a24bec68-9459-43f4-8765-933c0c1f2490%40googlegroups.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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