Flow controller (water presence)

It is used to check for the presence of liquid inside a pipe or container. Its typical application is the secondary protection of submersible pumps from “dry” operation. It is connected to a spark plug type electrode. Its operation is based on measuring the change in resistance between the electrode and the ground. By connecting the supply voltage, the relay arms for an adjustable time T. It then checks for the presence of liquid and remains armed if there is, or disarms the output relay if not. The use of safe low AC voltage between electrode and ground prevents electrolysis. The impedance of the liquid should be less than 20 kΩ. Note: the PT415L type is also available. if it detects an error (no water presence) in the electrode then deactivates the relay and “locks” the error.