With OH4, what’s the recommended way of doing calculations against two or more things to produce an item?
I’ve got a few places I’d like to do this, but the obvious one is to use humidity and temperature data to calculate dew-point. These are separate channels (for me, this is separate topics from MQTT). I’d like to do a transformation, but this works on a single channel input.
Thanks.
You will have to use a separate Item for the dewpoint, use a rule to calculate the value and update the Item from there.
As you have both, temperature and humidity information, available in the same mqtt thing, you can calculate the drew point in a script transformation and add it as a channel to your mqtt thing.
The script transformation will receive the entire mqtt message, needs to extract temperature and humidity and then calculate the drew point
If needed I can share an example tomorrow
Looks like the Weather Calculations binding is the only way to go here.
Each of my MQTT entries have a subtopic, so there’s no one single message JSON that I can run through a parser and cherry pick multiple entries.