Variable area flowmeters, also known as rotameters, are devices used to measure the flow rate of liquids (and gases) in various industrial applications, including water treatment and chemical processing. These meters operate on the principle of a float moving within a tapered tube in response to fluid flow, with the float's position corresponding to the flow rate. Variable area flowmeters offer a simple, cost-effective, and reliable solution for flow measurement, making them a popular choice for a wide range of industries.