Having options is always a great thing. There are many different types of flow meters on the market. The common principles of flow meters are differential pressure, velocity, positive displacement, mass, and open channel. Along with the principles the different types of meters are orifices, venturies, nozzles, rotameters, pitot tubes, calorimetrics, turbine, vortex, electromagnetic, doppler, ultrasonic, thermal and coriolis.
Because there are so many different types, making sure you have the right one for the project is imperative. Each meter does different things and reacts differently depending on what you need it for. The basic goal is to get the most accurate reading.
For more information on what all these flow meters do visit Engineering Toolbox HERE