The video (not mine!) explains the settings of a similar system I am using. For more info, go to http://openenergymonitor.org/emon/
Other sites where I publish live data: http://daturach.github.io/
Soil humidity (tension) is measured in a pot with plants (Tradescantia fluminensis). The tensiometer is made with parts from Blumat, Austria and an Arduino connected to PC. See the 'More Information' tab to the right.