The third most common flow meter, behind differential pressure and positive displacement flow meters, is the magnetic flow meter, also technically an electromagnetic flow meter or more commonly called a MAG meter.
The following link takes you to a short video describing the origins of the MAG meter, its functions and how flow is measured. DCA does not endorse a specific product, but wants to inform operators across the state about equipment that could potentially help their treatment process.
Any time you install new equipment, do your research to make sure it will work for your purposes. Hence, with MAG meters, the location is important because it cannot be placed next to an angle in a pipe line.