Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways. A flow meter (or flow sensor) is an instrument used to measure linear, nonlinear, mass or volumetric flow rate of a liquid or a gas. When choosing flow meters, one should consider such intangible factors as familiarity of plant personnel, their experience with calibration and maintenance, spare parts availability, and mean time between failure history, etc., at the particular plant site. It is also recommended that the cost of the installation be computed only after taking these steps.