Flow Meter Types: Rotameters and Mass Flowmeters PurityPlus® has a wide variety of flow meter types, from rotameters and mass flowmeters to a nitrogen flow meter or co2 flow meter, we're sure to have the gas flow meter you're looking for. We also pride ourselves on providing the highest quality equipment. Because of this, our flowmeters have the most accurate indication and precise control of fluids and gases and available for a wide range of applications. Flowmeters are used to measure the rate of flow of liquids or gases. They do not control the rate of flow unless they are equipped with a control valve or flow controller. There are two basic types of flowmeters; rotameters and electronic mass flowmeters. These versatile gas flow meters are functionally and dimensionally interchangeable with other current designs and incorporate many innovative features. Rotameters Rotameters provide a simple, precise, and economical method to measure flow rates. These devices consist of a precision tapered glass tubing containing one or more spherical floats with a measuring scale etched on the glass tube. As fluid enters the tube, the float rises to a point where the area between the float and the tube wall is large enough to permit unrestricted flow, and the float is stationary. This position corresponds to a point on the tube scale and thus permits a reading of the rate of flow. The capacity, or flow range of a tube can be varied by changing the float material. Rotameters, unlike mass flowmeters, are affected by temperature and pressure variation. When equipped with a control valve on the inlet, readings are correct as long as the outlet pressure is equal to the pressure at which the tube was calibrated. When a valve is installed on the outlet, the tube calibration pressure must match the inlet pressure to the flowmeter unit. Mass Flowmeter and Controllers Thermal mass flow controllers can be more reliable than volumetric flow devices like rotameters because they are relatively immune to changes in gas temperature and pressure. Because these instruments measure molecular flow, they provide the most reliable, repeatable and accurate method of delivering gas to your system. PurityPlus® ' Series 810C MassTrak is designed to control the flow of non-corrosive gases and its built-in display and set-point control eliminate the need for separate power supply and readout electronics, both of which are standard on most mass flow controllers. Likewise, PurityPlus® ' Series A820 electronic mass flowmeters are compact, self-contained units designed to indicate the flow rate of gases. Unlike variable area meters, flow rates are unaffected by variations in temperature and pressure within specified limits.