A Flow Sensor or a Flow Meter, is a device used to quantify the volume of fluid passing through a point in a pipe. Reed Switch based flow sensors are built with a paddle having multiple magnets or a single multi-pole magnet that continuously triggers the reed switch to generate a square wave output that can be translated to volume of fluid.
Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. The common types of flowmeters that find industrial application can be listed as below:
Flow measurement methods other than positive-displacement flowmeters rely on forces produced by the flowing stream as it overcomes a known constriction, to indirectly calculate flow. Flow may be measured by measuring the velocity of fluid over a known area. For very large flows, tracer methods may be used to deduce the flow rate from the change in concentration of a dye or radioisotope.