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Unexpected sea-level pressure adjustment *solved*

Posted: Fri Mar 07, 2008 12:01 pm
by skyewright
Reading I'm not sure if this is a Meteohub or an RFXCOM thing, but...

Under Weather Station => Options => Sea Level Pressure, I have set \"use reading from weather station\".

However, in Sensors I see:

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BTHR918N 26 min	17.0° 68% 967(979)mb fc:0
The 979 looks to be a sea level pressure based on my 100m altitude.

Dashboard shows the 979 as 'sea level'

The WD export file uses the 'adjusted' 979 figure, e.g.

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 7  3 2008  9 37 5.4 86 320.0 978.8 15.1 16.2 234 0.0 -999 -999 -999 5.4
So, is the sea level value arriving from the sensor (seems unlikely as I don't think the BTHR918N has anyway of knowing altitude or offset), or is it being calculated by Meteohub?

Background: I'd been aiming to use the WD export file as a handy format for gathering evidence of a possibly faulty BTHR918N unit (I can present that and the WMR200 based equivalent for comparison) - so I'd prefer the unadjusted figure, as I thought I'd set in Weather Station.

Any ideas?

Re:Unexpected sea-level pressure adjustment

Posted: Sun Mar 09, 2008 12:42 pm
by admin
Hi,
in rfxcom mode Meteohub just gets the pressure reading fro the sensor. Therefore, the option \"take sea level pressure from weather station\" cannot be applied correctly., as there is no sea level pressure reported by the sensor. In this case Meteohub computes the sea level from the stations height as specified in Meteohub's settings page.

Re:Unexpected sea-level pressure adjustment

Posted: Sun Mar 09, 2008 1:23 pm
by skyewright
admin wrote:Hi,
in rfxcom mode Meteohub just gets the pressure reading fro the sensor. Therefore, the option "take sea level pressure from weather station" cannot be applied correctly., as there is no sea level pressure reported by the sensor. In this case Meteohub computes the sea level from the stations height as specified in Meteohub's settings page.
Meteohub is you program so your logic counts, but my logic would be that in the situation of "user says, use the station sea level figure, but station has no sea level figure, just use the figure that the station does provide". If the user wants meteohub to do a calculation in that case they can easily set one of the other two options (i.e. altitude, or altitude & temp).

However if you can provide the 'calibration offset' requested elsewhere I think I can make the problem[1] go away and we can be all be happy. :)


[1] My possibly badly set barometer, for which I'm trying to collect evidence.

Re:Unexpected sea-level pressure adjustment

Posted: Sun Mar 09, 2008 2:01 pm
by admin
Hi,
your arguments do convince me. The next update will provide raw pressure data in the case of a rfxcom when the switch is set to \"take sea level pressure from weather station\".