The hardware is consists of an Arduino microcontroller (here an Arduino Uno R3) and a pre-wired soil moisture sensor module. The soil moisture sensor module , built around the LM393 comparator, gives ...

Thus, the output frequency varies by approximately ±64.5 kHz around 106 kHz for an input change of ±100 mV from 0 V. This circuit's accuracy is better than 0.2% of full scale.