A post was split to a new topic: Pressure reading high
My pressure readings are also too high. My height calibration is very close to actual, as good as I can get it. The pressure reading is about 2 to 3 mb too high. I was told that this would automatically calibrate but I haven’t seen any evidence of change
Please let us know what your Station ID is and I am sure one of the members of the forum will be able to help.
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Where do I find the ID? Is it the name or some number.
Press the Gear in the top left corner.
Press Stations.
Press the Station Name.
Press Online in the lower right corner.
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@moeythomas Thought it best to continue the discussion here instead of highjacking the WX Console thread! Perhaps @eric might want to merge some topics together to keep things clean.
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Yes. Absolutely, that’s the correct way to do it. However, the reading will be back-to-front, because weatherflow are doing it wrong.
I’m not sure I’m following. Sorry!
The Air module measures absolute pressure. This is what is sent to the WF servers and what you can download from the API. This needs to be corrected for the station elevation, however, to get sea level pressure, and it is sea level pressure that is displayed in the WF app. So changing your elevation in the app will change the reported sea level pressure.
Am I missing something?
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You are missing something - it’s categorically wrong. I’m reading the Davis manual right now…
When adjusting my elevation on the WeatherFlow app, I have to put it minus 40ft to get a figure that matches my Davis. That bit is clearly wrong!
On the Davis, you input your correct elevation, then adjust your console/stations pressure to the nearest correct observation. Once done, you get a calculated sea level pressure from it.
WeatherFlow are doing it the wrong way around. Their elevation adjustment is changing the sea level pressure, it should be changing the reading at the module, which will then calculate the sea level pressure.
It speaks for itself, surely? If I am having to put in an elevation of 40ft below sea level, then something is clearly wrong, isn’t it?
OK - I think see what you are saying.
This is a calibration problem though, right? If I understand correctly you enter the correct elevation into your Davis station and then you manually adjust the station pressure measured by the Davis unit to match it to some nearby trusted source. So in a sense you are adding a custom calibration to your Davis unit to report the best station pressure you can, and then combined with the correct elevation you get the best sea level pressure.
Unfortunately you can’t apply the same direct calibration to the station pressure measured by the Air module. So if my understanding is correct, the station pressure measured by your Air unit and you Davis unit are going to be different. You can see the station pressure in the text display on the WF app so you should be able to see how big the difference is. Therefore if you apply the same elevation to calculate sea level pressure, you end up with a different value to your Davis unit. As you can’t apply a direct offset to the Air station pressure, the only way to get the sea level pressure to read the same is to fudge your elevation - in this case -40ft below sea level.
Am I along the right lines?
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Or, let weatherflow know that your station pressure is not correct. They will check it and adjust as necessary.
That’s absolutely correct. I should be able to enter my correct elevation (10m above sea level) then adjust the station pressure to a reliable source and bingo, you get a calculated sea level reading.
If I set my correct elevation in the WeatherFlow app, the sea level pressure is adjusted, but station pressure remains unchanged, and that is also incorrect when comparing to my Davis VP2 and Vue console, as well as nearest observations.
The simplest form I can put it in is that the sea level pressure on the app is showing what my station pressure should be, and station pressure is showing something else.
The easiest way currently would be to compare the Air to a known pressure reading, say from a nearby Airport during nice stable high pressure and adjust the station altitude till it matches.
Moved a few posts over to this one though it isn’t always easy where to cut … hope it is still cleanr
the discussions started in this topic and drifted to barometric values
Hope everyone can still follow …
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I understand what you are saying now, and it seems to me that you might have a dodgy Air module. Out of interest though, how does the station pressure measured by the Air compare to the station pressure measured by your Davis unit before you apply your manual adjustment to make the Davis unit match your trusted source?
I ask because I don’t see the same issue as you. Once I have entered the correct elevation for my Air, it reads the same SLP (within 1 mb) as a professional grade station about 10 km away.
(@moeythomas I moved this down to try and keep the thread flowing after the merge!)
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If I put in my elevation of 33ft asl, then the sea level pressure is 3mb too high. Station pressure remains the same regardless of putting in a positive or negative number.
edit:
Bournemouth airport: 1014.4 hPa
My Davis stations: 1014.4 hPa
WF slp with correct elevation: 1017.2 hPa
WF slp with -40 feet: 1014.4 hPa
That’s the problem right there… you shouldn’t need to adjust the elevation until it matches a sea level pressure. Firstly, that’s the incorrect way to do it. Secondly, I have to put in a minus figure to get it to match anyway.
I’m wondering if anybody here is using a Davis or Oregon station? I have both a VUE console and a VP2 console, as the manual states, you put in your elevation, and then adjust the console/station pressure. It’s the same on an Oregon WMR200. If you search any weather forums eg Cumulus, Netweather, Weather-Watch, WX forum, people with Davis hardware will say that it is the station pressure that get’s adjusted. Once your elevation settings have been correctly put in, the sea level pressure will be calculated.
I assume the 1014.4 hPa is SLP from your Davis station. What is station pressure for your Davis station, before you have made any adjustments? How does it compare to the 1015.7 mb currently being reported as station pressure from your Air?
What a time to run out of popcorn.
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Hi @moeythomas . We agree that having to fudge your elevation to calibrate your sea level pressure is NOT THE RIGHT APPROACH…and to be clear, this is not the approach that WF is taking.
Here is how it actually works: AIR will sense the pressure at it’s location (station pressure). To normalize and compare against other stations in the area, total elevation needs to be taken into consideration…which is then used to calculate sea-level pressure…so that everyone is comparing apples to apples. For your WF system, total elevation = [elevation at your location automatically determined when you set your geo-location] + [height above ground at which the AIR is mounted].
In-situ sensor calibration is typically done by comparing known good data sources and applying a calibration. Unlike Davis et. al. we don’t think this should be something that the average home user (or anyone for that matter) should need to do. INSTEAD, the WF auto-calibration / continuous learning (CL) system will automatically identify and monitor a variety of known good data sources for your immediate area and automatically compare them to your AIR data on an ongoing basis and apply any required calibration.
As mentioned previously, the WF CL system has not yet been fully deployed. As of today 19 Sept, only RH is run through the daily CL calibration system. Other parameters including Pressure is in final testing and will be rolled out soon.
So there you have it…we agree! Have faith, we’re not idiots. 
Will announce when the CL system is deployed for Pressure.
And PS - we suspect that a batch of AIRs did not receive a proper pressure sensor calibration at the factory which might explain the 2-3mb deltas being reported.
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In other words… WeatherFlow IS doing it correctly.
WeatherFlow is an expert company staffed by experts in weather.
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