Fluid flow controller and method of operation

A fluid flowmeter for measuring the mass flow of a known fluid composition said flowmeter comprising:

• a body including a fluid flow passage therethrough;
• a flow restrictor interposed in said flow passage in said body;
• a first pressure sensor for sensing fluid pressure in said flow passage upstream of said flow restrictor and a second pressure sensor for sensing fluid pressure in said flow passage downstream of said flow restrictor;
• a temperature sensor for sensing the temperature of fluid flowing through said mass flow controller;
• and
• a control circuit operably connected to said first and second pressure sensors and said temperature sensor for measuring the mass flow of fluid through said flowmeter based on a differential pressure across said flow restrictor determined by the difference between said fluid pressures sensed by die first and second pressure sensors respectively, said fluid pressure in said flow passage downstream of said flow restrictor, and said temperature of said fluid flowing through said mass flow controller.

A method for controlling the flow rate of a fluid to a process comprising:

• providing a fluid mass flow controller having a body, a flow passage through said body, a flow restrictor interposed in said flow passage, a first pressure sensor for sensing fluid pressure upstream of said flow restrictor in said flow passage, a second pressure sensor for sensing pressure in said flow passage downstream of said flow restrictor, a temperature sensor for sensing the temperature of a fluid flowing through said fluid mass flow controller, and a control valve upstream of said flow restrictor for controlling the flow of said fluid through said flow passage and said flow restrictor;
• measuring the pressures of said fluid flowing through said flow passage with said first and second pressure sensors;
• determining a differential pressure across said flow restrictor based on the difference between the pressures measured by said first and second pressure sensors;
• measuring the temperature of said fluid flowing through said fluid mass flow controller;
• determining the mass flow rate of said fluid flowing through said controller based on said differential pressure across said flow restrictor, said pressure measured by said second pressure sensor, and said temperature measured by said temperature sensor;
• and
• operating said control valve to vary the flow of fluid through said flow passage until the mass flow rate of fluid flowing through said flow passage is substantially at a predetermined setpoint of mass flow rate of said fluid.

A method for measuring the mass flow rate of a fluid, comprising:

• providing a body including a flow passage and a flow restrictor interposed therein;
• flowing said fluid through said flow passage and measuring the pressures of fluid flowing through said flow passage upstream and downstream of said flow restrictor;
• measuring the temperature of said fluid flowing through said flow passage;
• determining the differential pressure across said flow restrictor based on the difference between said pressures of fluid upstream and downstream of said flow restrictor;
• and
• comparing said differential pressure across said flow restrictor, said pressure downstream of said flow restrictor and said measured temperature with a data set of mass flow rates of said fluid being flowed through said flow passage for various differential pressures across said flow restrictor and various pressures of said fluid downstream of said flow restrictor at a given temperature that is at least proximal to said measured temperature.