Fluid flow measurement is used in almost every process from small-scale medical applications to large petroleum refineries. Industries use flow metering devices to regulate the amount of chemicals to be reacted or separated in a continuous process and accurately determine the production rate. Flow meters are also indispensable in the supply of utilities such as water and gas to your home. There are many types of flow meters used in industry, but all flow meters need to be calibrated.

A rotameter consists of a graduated tapered glass tube mounted vertically in a frame with the larger end up. The fluid flows upward through the tapered tube and suspends a float (or bob) in the flowing stream. The float indicates the relative flow rate of the fluid using the graduations on the glass scale. Measurements using the float are made at its largest cross-section which is at the center of a spherical float.