Barometer problems

[Doug]

I am sending weather to both wunderground and pws weather from a station and the barometer reading are different at both sites. I see some barometer correction in the code for wunderground but nothing for pws weather. Anyone else having problems with this? I have the WS2080 set to absolute pressure. If I set it to relative then the reading for wunderground come out very high - probably due to the correction in the code.

I don't think either site does any correction for altitude. What should really happen here is you should set the realative correction in the WS2080 for your altitude and then use relative as the number sent to the services.

Any comments?

 

Doug Crompton
WA3DSP
www.crompton.com

[Doug]

Ok not many listening here so I investigated and will answer my own question.  There is a correction that was added to the C code for sending relative pressure to wunderground. Unfortunately this was not done in the code for PWS weather. PWS Weather just sends absolute pressure which would be wrong if you were not at or close to sea level. My first station was at seal level so I did not discover the problem until I put another station online at  360 feet. Here are the changes needed -

This is the existing code in fowsr.c , cwf_write  for wunderground -

// Calculate relative pressure
                                        wug_format[WS_WUG_PRESSURE].offset+=(CWS_unsigned_short(m_buf+WS_CURR_REL_PRESSURE)-CWS_unsi
gned_short(m_buf+WS_CURR_ABS_PRESSURE))*(WS_SCALE_HPA_TO_INHG);

What I did is add the same code with pws parameters in the PWS section of cwf_write -

 // Calculate relative pressure
                                        pws_format[WS_PWS_PRESSURE].offset+=(CWS_unsigned_short(m_buf+WS_CURR_REL_PRESSURE)-CWS_unsi
gned_short(m_buf+WS_CURR_ABS_PRESSURE))*(WS_SCALE_HPA_TO_INHG);

You also need to add in fowsr.h -

#define WS_PWS_PRESSURE         6

recompile and the reported pressure will be the same for wug and pws. Set the relative pressure in the WS2080 easy weather setup to match your local pressure from a respected source.

I wish someone was still maintaining this code. So the bugs could be officially fixed.

Doug

 

Doug Crompton
WA3DSP
www.crompton.com

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From: Doug <dsc...@yahoo.com>
To: "fo...@googlegroups.com" <fo...@googlegroups.com>
Sent: Wednesday, September 26, 2012 4:38 PM
Subject: Barometer problems

[Josch 600]

Has now been fixed in V2.0

Josch