Patent ID: 8386083

Claim:
A valve system that allows a required value of a valve cracking current of a mass flow controller to be updated, the mass flow controller being configured to control a flow rate of a fluid through the valve system, the valve system comprising: a valve movable in response to a valve current between an open position and a closed position to adjust the flow rate of the fluid to a desired set point, the valve being configured to begin to move to the open position when a valve current substantially equals the valve cracking current; and a valve controller configured to control the valve so as to adjust the flow rate of the fluid until an actual measured flow rate of the fluid substantially equals the desired set point, the valve controller being further configured to: (a) monitor the valve current and the flow rate of the fluid, while the valve is moving to the closed position and the valve current and the flow rate are both decreasing; (b) measure a value of the valve current when the fluid has a near-zero flow rate; and (c) update a previously determined value of the valve cracking current for a next run of the mass flow controller, by setting the updated valve cracking current to the value of the valve current at the near-zero flow rate; wherein the near-zero flow rate is defined as a predetermined percentage of maximum flow rate through the valve.