BME280 callibration- modifying the temperature changes the pressure reading?

Configuration
1

Hi everyone,

Bit of Noob here so be gentle. I’ve successfully added a BME280 temperature, humidity and pressure sensor to HA. The temperature readings are too high so I added (as per the guide in HA here the following line to the configuration.yaml file:

sensor
     - platform: bme280
       delta_temperature: -2.5

This brings the temperature reading into line with other thermometers, but also seems to have done the same with my pressure readings:

image
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I can’t see how this could happen. There’s a double step change in the above graph as I made another deta_temperature change to see what would happen, and as you can see it stepped down with a D-temp of -3.5, and jumped up when I changed it to -2.5. Very strange!

Any ideas on how to limit the change to temperature readings or is this a limitation of the BME board?

Thanks in advance,

Paul.

2

The ideal gas law. PV=nRT.

Pressure (P) is temperature (T) dependant. There’s a calibration factor dependant on temperature of the device.

3

Wow, that is a brilliant answer, thanks! The board is much smarter than I imagined. I’d assumed it would just measure them mechanically so there’s a lot of learning here. Thanks again!

4

Does the pressure reading line up with what your weather service is saying?

5

Actually if doesn’t seem too. Right now the Met Office UK and Met.no both say it should be 1021, but I’m reading 990. So that’s quite a bit out.

6

Pressure is also dependent on altitude, not sure if the integration takes that into account. In comparison ESPHome explains in a bit more detail how you could adjust the readings: BME280 Environment — ESPHome

7

Thanks, that’s very useful. Much appreciated!