I'm attempting to adjust / calibrate / modify the relative humidity readings of a BME280 sensor.
Just like everyone else, my BME280 sensors read a little high on the temperature side. But not as much as a lot of people claim. I'm only reading 1.0 - 2.0F degrees high, at average room temperatures 60-70F.
I've electrically verified that my code does not cause unnecessary self heating, as when the code is not taking a measurement, the sensor draws 0.2uA @ 3.28V.
So here is my question. If I have a very accurate external temperature reading, can I do the following to make the relative humidity reading more accurate:
Take a relative humidity and temperature reading from the BME280
Convert the 2 measurements to dew point
Take a temperature reading from an external temperature sensor and use that along with dew point from above to convert back to relative humidity
I doubt that's going to improve your reading, it may even introduce error, as the moisture sensor of the BME280 is at the temperature of the BME280, not at ambient temperature.
What you missed is that the problem is not where you think it is.
The BME measured temperature is the correct one for temperature compensation of the humidity sensor. That's why it's being measured to begin with, self heating and all.
wvmarle:
The BME measured temperature is the correct one for temperature compensation of the humidity sensor. That's why it's being measured to begin with, self heating and all.
How can a humidity sensor output a relative humidity value if it's doesn't know accurately what the current ambient temperature is?
That's what the word relative in relative humidity stands for. It's relative to ambient temperature.
This doesn't seem like an overly complex question.