Last Updated or created 2023-08-18
Example uses a shelly sensor, which has a offset mode in its new firmware. So below is not needed any more.
But the example can be used for any calibration/adjustments.
I’ve put two examples in the NodeRed function
First the solution
var temperature=msg.payload.tC; var humidity=msg.payload.tF; // calc new offset example // simple offset + 2.3 off real measurement msg.payload.tC=temperature + 2.3; // more complex example // take two measurements (with a big difference) msg.payload.tF=1.11 * (humidity - 1); return msg;
First adjustment is plus or minus a value.
Second is more precise when the temperature needs more adjusting
Dots on the red line are measured values
Blue is how it should be
So measured was 2.8 but should be 2
And measured 14.5 but needs to be 15
slope = (14.5-2.8)/(15-2) = 0.9
To get the multiplication factor = 1/0.9 = 1.1111
=(2.8-heightadjust)*1,1111 should give us 2
2/1.1111 = 2.8 – heightadjust
1.8 = 2.8 – heightadjust = 1
So the formula is realhumid = 1,1111 * ( measuredhumid – adjust )