barometer pression problem

[rpedroletti]

Hello,

I'm using a WMR928NX at 1250m in France.

I installed cumulus instead of virtual weather station. Yesterday, cumulus was showing the correct pression in barometer (~1000 hPa), but this night, it suddenly raised up to ~1250hPa, but I didn't change anything. In order to check, I relaunched VWS this morning, and it's showing the correct measure. Actually, my station console is showing 999hPa at sea level.
After reading this forum, I understood I had to calibrate cumulus. So I add a ~-250 offset in the calibration window.

My question :
- am I right ?
- what did it work yesterday and not this morning (it started to go wrong near midnight) ?

Thank you for helping.
Richard

[adam5]

Hi Richard,

What lead you to believe you needed to "calibrate" cumulus by adding a pressure offset in the calibration window? Normally, the calibration functionality in Cumulus (and various other weather station software packages) is used as a "fudge" factor, when a sensor and/or console cannot be calibrated or sited properly. Think of it as a "last resort" feature to correct bad data.

In your case, as long as you have correctly programmed your site elevation into your weather station console, you should not need a pressure offset programmed into Cumulus. Any adjustments to the pressure should be done at the console itself.

Not sure why it took a day for the pressure offset to take effect.

Hope this helps.

-Brian

[rpedroletti]

Thank you for helping.

I just made this test :
- set barometer calibration offset to 0 and restarted cumulus : barometer shows 1256 hPA instead of 1000hPa
- my wmr 928N console is actually showing 1000hPA at sea level.
- I setup cumulus with my current eleveation to 1250m
- Virtual Weather station is showing the right pressure : 1000hPa.

I remember after installing cumulus that the pressure was correct in cumulus, and suddenly, it started to show weird measures.

Where is the problem ?

[steve]

If you are running a version of Cumulus which has "debug window" on the view menu - open the debug window, let it run for a couple of minutes, then copy the contents of the window here.

If your version of Cumulus does not have the debug window, turn on the debug log, let it run for 5 minutes, then attach the debug.log file here.

Thanks.

[adam5]

Hi Richard,

Have to admit, with the pressure offset set to 0, I don't immediately know why there is a difference between your console pressure value and Cumulus. Hopefully Steve will have some insight for you.

But I have to ask, are you certain that you are located at an elevation of 1250 meters above sea level? That's over 4100 feet above mean sea level. You could be...but I'm just checking since that's pretty far up there. Maybe 1250 feet which is 381 meters? Reason I ask, setting you elevation in Cumulus to over 4100 feet might result in a pretty beefy sea level pressure calculation, and account for the differences in the console/software values if the console is set to 1250 feet.

-Brian

[steve]

Reason I ask, setting you elevation in Cumulus to over 4100 feet might result in a pretty beefy sea level pressure calculation, and account for the differences in the console/software values if the console is set to 1250 feet.

It's a reasonable suggestion, but Cumulus just reads the pressure and offset from the station and adds them together. The '256' part of the 1256 makes me wonder if the unofficial protocol spec I'm working from has an error and I am using one of the bits in the calculation which I shouldn't (or there is bug in my interpretation of the spec). But it's odd that no-one else with an Oregon Scientific has apparently seen this before.

[rpedroletti]

But I have to ask, are you certain that you are located at an elevation of 1250 meters above sea level? That's over 4100 feet above mean sea level. You could be...but I'm just checking since that's pretty far up there

I live right there http://fr.wikipedia.org/wiki/Les_Molunes, so I confirm my station is at 1250m above sea level.

If you are running a version of Cumulus which has "debug window" on the view menu - open the debug window, let it run for a couple of minutes, then copy the contents of the window here.

Please find as an attachment my debug file.
I run cumulus 1.8.8 build 881

[adam5]

Wow, you are up there. That's a beautiful countryside BTW.

Hopefully Steve can get you fixed up.

-Brian

[steve]

Please find as an attachment my debug file.
I run cumulus 1.8.8 build 881

There are two types of internal sensor; it looks like the protocol spec I have for your type is incorrect. I'll try to sort it out and get a fix out.

[rpedroletti]

OK. I'm ready to test it as soon as you released it.
I Thank very much.

[steve]

Please try build 891:

http://www.nybbles.co.uk/downloads/beta ... sSetup.exe

[rpedroletti]

it's ok this time. Thank you for this quick fix.

- Can I consider this version as stable, or should I wait for a release ?

Richard

[steve]

It's up to you, but it will probably be quite some time (weeks or months) before 1.8.9 becomes the "official" release. Many people use the beta versions all the time without problem.