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[Pro2 PLUS] AQM II - "cal" connector
Back from holidays and building my new AQM; l notice on the pcb a connector labeled “cal”, could you please explain the use of this connector.
Is there a schematic available?
Hello Jim,

The connector labelled "cal" is connected to HD pin on the MH-Z19B sensor, used for a manual ZERO point calibration. Usually doing a ZERO point calibration isn't necessary.
For more info refer to MH-Z19B datasheet:
MeteoCercal - Air Quality Data
Click here to watch at my ThingSpeak channel


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