Airpressure offset

[Aint-Nobody]

Hi all,
When I configure an altitude to correct the displayed air pressure, the device is not at sea level.
However, the software then displays it exactly the wrong way around. Is there a reason for this, or am I making a mind mistake?

[sfromis]

You did not post any data or examples about what you mean by "the wrong way".

What I see when configuring Altitude near sea level is like this:
"Pressure":1016.44,"SeaPressure":1018.26
Hence it did calculate the sea level pressure to be a bit higher than the pressure where the sensor is. Looks ok to me.

[Aint-Nobody]

Okay, let's look at an example with fictitious values:

Suppose I'm at an altitude of 100 meters and the current air pressure displayed in Tasmota is 1000 hPa. The real actual air pressure at this location in 100m height is 1020 hPa.

Now I configure the altitude to 100.
Then it displays:
pressure 1000, seapressure 1020.

Pressure refers to the current altitude, and
Seapressure means air pressure at sea level, i.e., 0 meters.
In reality, air pressure decreases with increasing altitude.

So, it should then correctly display, for example: pressure 1020, seapressure 1040.

Or even simpler, just omit the value for Seapressure and display the calculated value as pressure.

[sfromis]

Right, air pressure does indeed decrease with higher elevation, and increase with lower altitude.

With "the current air pressure displayed in Tasmota is 1000 hPa", this is what the pressure sensor detected as "the real actual air pressure at this location", which is not affected by configuring an altitude of 100 meters.

What you obviously can predict is that the physical air pressure at sea level will be higher, like 1020 hPa (technically not the right number, but never mind). And this matches what Tasmota reports.

What configuring Altitude gives is not an offset to change the "Pressure" reading, but instead to add a new field with a calculation of what higher (or lower in a few places) sea level pressure matches the altitude. With an altitude of 0 meters, Tasmota does not add the "SeaPressure" field.

[Aint-Nobody]

Okay, I understand your explanation.

It's still confusing, though.
I assumed that configuring altitude would mean an offset for the pressure, similar to temperature offset.
That would make more sense.

Because, for example, if I want to set my watch, I'm changing the currently displayed local time. I'm not interested in what time it is in China. 😂

Thanks anyway for your clear answer.