CPC G05D 7/0623 (2013.01) [G01F 1/00 (2013.01); G01L 9/0098 (2013.01); G05D 7/0617 (2013.01); G05D 7/0647 (2013.01); G05D 7/0635 (2013.01)] | 18 Claims |
1. A mass flow controller for controlling fluid flow rate, the mass flow controller comprising:
a valve assembly comprising at least one valve and being in fluid communication with at least one upstream location and at least one downstream location in a same flow path as the upstream location, wherein the at least one valve has a valve stem and a valve seat;
at least one semiconductor based pressure sensor in fluid communication with the at least one upstream location and the at least one downstream location;
a position sensor communicably coupled with the at least one valve; and
a controller communicably coupled with the valve assembly and the at least one pressure sensor, wherein the controller is configured to:
determine pressures for the upstream location and the downstream location; and
control the valve assembly to adjust a valve stroke of the at least one valve in fluid communication with the upstream and downstream locations based on an actual fluid flow rate and a desired positive fluid flow rate;
receive a value indicative of a measurement of an actual position of the valve stem from the position sensor as the valve stem moves from the valve seat following the adjustment; and
perform diagnostics on the mass flow controller by comparing the actual position of the valve stem relative to a predetermined position of the valve stem, the predetermined position of the valve stem determined in response to the desired positive fluid flow rate, the predetermined position determined from a predetermined relationship between the pressures for the upstream location and the downstream location and the position of the valve stem, and determined from a predetermined relationship between the desired positive fluid flow rate and the valve stroke.
|