Is it interpolated to 0 deg C and 0% rH and 0% pressure or what?
Exactly, even though it's only an academic value I can correct the values to "any condition" I want.
However, for me my measurements are showing, that each precision voltage reference should contain sensors for temperature, humidity and pressure! I have evaluated different sensors and will use SHT25 and MS5611 for my next designs. Also I got an own feeling of what a case and the electrical connections through the case should look like. I think that is a very important point, if you want to do precision stuff you must run all the way through the dessert and do all the mistakes on your own to develop a gut instinct.
It gets not clear to me: you did the correlation one after the other or all coefficients together or incremental (with correction of the previous coefficients)?
1. I first compensated for the most significant variable, temperature.
2. After this I compensated the temperature compensated values for humidity (the second significant variable) and
3. at least I compensated the temperature and humidity compensated values for ambient pressure.
With your words: the incremental way.
On the first view the dew point temperature seems to be better than rH for humidity.
Dew point is a calculated value including temperature and humidity using Magnus approximate formula, I wouldn't use that to compensate for humidity.
But since the time constants for humidity are in the 3-7 day range a correlation with a pt1 filtered dew point temperature would be also interesting.
Still I don't understand what you mean by "pt1 filtered". Maybe you can give me an example?