This water sensor works by having a series of exposed traces connected to ground and interlaced between the grounded traces are the sens traces. The sensor board has a demension of 5.0 x 4.0cm. There is also a on-board potentiometer to adjust the sensitivity, you can get the amount of water induced contact between the grounded and sensor traces.With the comparator LM393, users can get both the analog signal and digital signal.
Connect this sensor to 5V power, adjust the sensitive, if there is not water in the sensor, D0 output HGHT(1), and the signal indicator off. if there is water in the sensor, D0 output LOW(0), and the signal indicator on. Aslo can using Arduino to get the analog output by connecting the A0, according to the value to caculate how much of the water.