But this autocorrection of drift seems not to work reliably
I discovered that this pressure-sensor has a drift over a longer time. (10 days)
After power off/on with no differential pressure applied I was able to re-calibrate it.
For automating this process I would need an extra valve that switches between measuring and calibrating
So if somebody knows of a sensor with a smaller differential-pressure range -50 Pa / + 50 Pa
that also has longterm-stability of the measured differential-pressure this would be a really good solution.
Second best solution is a small elektromagnetic gas-valve that switches between measuring pressure inside the chimney and outside the chimney for calibration.
As the pressure is so small I have doubts if a standard pressured air valve will work.
Maybe a small ball-valve moved by a RC-servo would be better suited.
I would have to place one sensor inside the chimney or build a sealed box with the sensor inside and have a connection between inside the box and the inside of the chimney through a silicon-hose.
The datasheet says:
RMS-noise 0,2 Pa (where the main range to measure is -15 Pa to +5 Pa (1% yes acceptable)
what I don't understand is
Offset temperature coefficient +- 1,5 Pa/K
Does this sensor have temperature-compensation or not?
If the sensor has temperature-compensation what does this spec mean?
well the datasheet says
When changing by e.g. 10°C at constant pressure / altitude, the measured pressure / altitude will change by (10 * TOC)
10K * 1,5 Pa/K = 15 Pa
Strange to me that they don't apply temperature compensation to the pressure measuring
In the meantime I found this sensor
Datasheet: Product Summary
The SDP600 sensor family is Sensirion’s series of digital differential pressure sensors designed for high-volume applications. They measure the pressure of air and non- aggressive gases with superb accuracy and no offset drift.
Let's see if the can hold what the promise. I ordered tqwo of those sensors
Generally it’s not a great idea to push the abilities of such a sensor if you want any sort of accuracy. 1.5% accuracy is 7.5 Pa and your range of interest is 50Pa , so your basic measurement accuracy for 50Pa is 15%. Not great .
For low pressures , you need a better performing ( more expensive) transducer . For very low pressure consider measuring flow instead - look at Honeywell micro bridge
