System and method for improved indicated flow in mass flow controllers
AssigneeHitachi Metals, Ltd.
InventorAlexei V. Smirnov
Life of this patent
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Abstract
A mass flow controller and associated methods for providing indicated flow from the mass flow controller are disclosed. The method may include obtaining a measured flow signal indicative of a mass flow rate of a fluid that is controlled by the mass flow controller and filtering the measured flow signal to generate indicated flow that provides a representation of the actual mass flow rate of the fluid. The indicated flow is provided to an operator of the mass flow controller, and a rate of change of the mass flow rate of the fluid is determined based upon samples of the measured flow signal. A time constant used in connection with the filtering is then adjusted based upon the rate of change of the mass flow rate.
Claims19
A method for providing indicated flow from a mass flow controller, the method comprising:
- providing a flow sensor signal from a sensing element circuit of the mass flow controller in response to a fluid passing through the mass flow controller;
- generating, with a processing portion of the mass flow controller, a measured flow signal from the flow sensor signal, the measured flow signal is indicative of a mass flow rate of the fluid;
- obtaining samples of the measured flow signal within a time interval and determining a rate of change of the mass flow rate of the fluid based upon the samples of the measured flow signal;
- adjusting a time constant used in connection with filtering the measured flow signal based upon the rate of change of the mass flow rate;
- filtering the measured flow signal using the adjusted time constant to generate an indicated flow that provides a representation of an actual mass flow rate of the fluid;
- and
- providing the indicated flow to an operator of the mass flow controller.
A mass flow controller comprising:
- a mass flow sensor that provides a measured flow signal indicative of a mass flow rate of a fluid;
- a processor to receive the measured flow signal and provide an indicated flow;
- and
- a non-transitory, tangible processor readable storage medium coupled to the processor and encoded with processor readable instructions for filtering the measured flow signal to provide the indicated flow, the instructions comprising instructions for:
- obtaining samples of the measured flow signal within a time interval and determining a rate of change of the mass flow rate of the fluid based upon the measured flow signal;
- adjusting a time constant used in connection with filtering the measured flow signal based upon the rate of change of the mass flow rate;
- filtering the measured flow signal using the adjusted time constant to generate the indicated flow that provides a representation of an actual mass flow rate of the fluid;
- and
- providing the indicated flow to the operator of the mass flow controller.
A mass flow controller comprising:
- a sensing element circuit configured to provide a flow sensor signal in response to a fluid passing through the mass flow controller;
- means for generating a measured flow signal from the flow sensor signal, the measured flow signal is indicative of a mass flow rate of a fluid that is controlled by the mass flow controller;
- means for obtaining samples of the measured flow signal within a time interval and determining a rate of change of the mass flow rate of the fluid based upon the samples of the measured flow signal;
- means for adjusting a time constant used in connection with filtering the measured flow signal based upon the rate of change of the mass flow rate;
- means for filtering the measured flow signal using the adjusted time constant to generate an indicated flow that provides a representation of the actual mass flow rate of the fluid;
- and
- means for providing the indicated flow to an operator of the mass flow controller.
Dependencies are inferred from the claim text.