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]> 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 > > <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 > <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 > <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 > <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] > <mailto:[email protected]>. > 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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