Flow switches. Here’s an excellent way of detecting water flow in a pipe. A “flapper” moves with water flow, actuating a magnetic switch on the outside of the pipe. An internal switch can send a signal to a warning system or to put in function or stop a heater, a cooler, a pump, etc.
The ST-9 is factory adjusted to close the circuit at 14 gpm and open it at 6 gpm, but is also field adjustable over a wider range. ST-11 and ST-12 have a selectable N.O./N.C. setting and can close the circuit at 13 and 1 gpm respectively.
The FS-2 product has a calibration screw for different applications. The V12-2 model gives a signal by contact when the flow is inferior to 0.5 gpm and can be used with chemical products.