By analyzing those patterns, an onboard Raspberry Pi microcomputer is able to determine the current water level to within an accuracy of plus or minus ~1.5 cm (0.6 in).

As the top sensor goes low (water above level C), the CLR signal is activated and the output of the flipflop is low. This allows Q1 to turn on and activate a triac or relay for the pump.

These low-cost water level sensors are made of a small solar panel, batteries and an alarm. When water levels start to rise, city officials will be alerted by the ping.