Mass Flow Controllers Enter Mainstream

In most processes the critical variable is mass, not volume. Volumetric flow measurements are less reliable than mass flow measurements because changes in gas temperature and pressure change the density of a fixed volume of gas. In the control system, additional errors can be propagated by backpressure fluctuations in the process being monitored. In contrast to rotameters, turbine meters, and other volumetric flow devices, thermal mass flow meters (MFMs) and mass flow controllers (MFCs) are relatively immune to changes in inlet temperature and pressure. The MFM/MFC is the only device capable of providing direct measurement of mass flow.