Introduction
Capacitive soil moisture sensors measures soil moisture levels by capacitive sensing rather than resistive sensing like the more common soil moisture sensors on the market. There are different brands, for instance DFROBOT SKU SEN0 193
To learn about the advantages with capacitive soil moisture sensors, view the Youtube instruction Why most Arduino Soil Moisture Sensors suck (incl. solution), lesson #207 by Andreas Spiess.
The capacitive moisture sensors used in the xspectrolum spectrometer are from pchbutik.