Below is a list of Flowmeters manufacturers from St. Louis, Missouri. Flowmeters are used to measure the flow of air, fluids and gas. Many flowmeters measure the volume of the material while other flowmeters measure the speed, and still other flowmeters measure the mass of the materials. For the most part, flowmeters are used to infer mass flow through calculations that flowmeters and flow monitor instruments make after taking various flow measurements, such as absolute pressure, differential pressure, viscosity and temperature.