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Thermal mass flowmeter and mass flow controller, flowmetering system and method

  • US 5,911,238 A
  • Filed: 10/04/1996
  • Issued: 06/15/1999
  • Est. Priority Date: 10/04/1996
  • Status: Expired due to Term
First Claim
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1. A flowmeter for use in a manufacturing process for controlling the flow of one of a variety of fluids used in the process, a process fluid being used in the process under a variety of temperature and pressure conditions, the process fluid flowing through a valve controlled in response to a flow rate sensed by the flowmeter and said process fluid being a toxic, reactive, expensive, or difficult to dispose of fluid, or a combination thereof, the flowmeter comprising:

  • means for sensing fluid flow through a passage by which the process fluid is directed to a process location at which it is used; and

    ,processing means producing an output signal representative of the sensed flow rate of the process fluid, said processing means including means for accessing a calibration curve for the flowmeter to determine the amount of process fluid to be delivered by said fluid flow valve based upon said sensed flow rate and a set point externally established by an operator of the process, said calibration curve being derived from a calibration data set accumulated for the flowmeter over the operational range thereof and using a calibration fluid which is not the process fluid now being controlled by said flowmeter, accessing said data set for said process fluid permitting said flowmeter to condition an output signal generated by the flowmeter so the output signal accurately represents the sensed flow rate of the process fluid so the valve through which the process fluid flows can be accurately controlled to meet the set point requirements of the process even though said process fluid is not the fluid with which the flowmeter is calibrated.

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