MKS Instruments, Inc.
Method and apparatus for pressure-based flow measurement in non-critical flow conditions

Abstract:

Methods, systems, and apparatus for pressure-based flow measurement are provided. A processor receives, from the pressure-based mass flow controller (MFC), an upstream pressure value P.sub.u. The processor computes, for the pressure-based mass flow controller (MFC), a downstream pressure value P.sub.d based on the received upstream pressure value P.sub.u. The processor computes, for the pressure-based mass flow controller (MFC), a flow rate Q based on the received upstream pressure value P.sub.u and the computed downstream pressure value P.sub.d. The processor controls a flow through the pressure-based mass flow controller (MFC) based on the computed flow rate Q. The methods, systems, and apparatus can be used for flow measurement in non-critical or un-choked flow conditions.