| 摘要 |
A valve system for a mass flow controller that controls a flow rate of a fluid is disclosed. The valve system includes a valve movable between an open position and a closed position to adjust the flow rate of the fluid to a desired set point, and a valve controller. The valve controller sends a valve current through 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 monitors the valve current and the flow rate when the valve is moving to the closed position, determines a value of the valve current when the fluid has near-zero flow rate, and updates the valve cracking current for a next run, by setting the updated valve cracking current to the value of the valve current at the near-zero flow rate.
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