It detects soil moisture levels, ambient temperature ... some probe-style meters in the ground can damage them, affecting their accuracy. Does a moisture meter also measure humidity?

To drive the 1940s era indicators, [Build Comics] is using an Arduino Nano and a DHT22 sensor that can detect temperature and humidity. A couple of trimmer pots are included for fine tuning the ...

If you want to measure humidity (and temperature, and maybe even barometric pressure) in a device that you’re building, have a look at this comprehensive test of seven different options.

Once set up, HomeKit will recognize the SwitchBot Meter Pro as a temperature and humidity sensor (though not as a CO2 monitor). That limitation aside, it still opens the door for useful automation ...