Abstract: A thermal mass flow controller having a thermal mass flow meter with an orthogonal thermal mass flow sensor includes a base defining a primary fluid flow path therein for carrying a flow of fluid to be metered. A pressure dropping bypass is positioned in the primary fluid flow path. A flow measuring portion of a thermal mass flow sensor is oriented substantially transversely or orthogonally with respect to and is in communication with the primary fluid flow path. The flow measuring portion includes a portion of an electrical bridge for determining a temperature of the sensor and produces a mass flow rate signal in response thereto. A valve is connected to an outlet of the primary flow path to control the flow of fluid in response to the mass flow rate signal.

Abstract: Method and apparatus for determining a mass rate of flow of gas by a rate of change of pressure includes an inlet for communicating a flow of gas from a source of gas whose mass flow rate is to be measured. A volumetric container is connected to the gas inlet to receive the gas. The volumetric container precisely defines a standard volume in its interior. Positioned within the volumetric container is a heat conductive assembly for maintaining the interior of the system substantially isothermal during pressure changes of the gas as gas flows into or leaves the container. Attached to the container is a pressure measuring transducer which measures the gas pressure within the container. The rate of change of the gas pressure under isothermal conditions within the container is indicative of the rate of mass flow of the gas into or out of the volumetric container.

Abstract: A modulating valve is described for controlling the flow of a working fluid through a flow orifice. The valve includes a encapsulated armature having a permanent magnet and a pair of soft iron pole pieces within its interior. The armature is axially movable by the passage of current through one or a dual pair of solenoid coils surrounding the armature. A thin webbed sealing disk is stretched over the end of an armature housing extension and acts to close or modulate flow of working fluid by varying the axial clearance between the disk and a stationary annular seat of the flow orifice. The armature is supported on flexure guide springs that allow armature axial motion when axial magnetic forces are applied to the armature. These axial forces are provided by the interaction of the solenoid coil(s) and the field of the permanent magnet.

Abstract: A mass flowmeter and controller measures the mass flow rate of liquid or gaseous fluids and controls the flow rate of the fluids being utilized in a processing operation. A series of flow channels and blocked channels are micro-etched from a silicon substrate leaving an integral membrane suspended across the channels. A heater-sensor thin film resistor, diode or transistor is formed on the membranes and the substrate during manufacture to sense the temperature at particular locations. A cover housing matching channels and grooves forms flow and stagnant blocked conduits in the structure. Through a bridge circuit a signal indicative of mass flow is produced. This signal is passed to a control valve armature coil in an in-line flow control valve.

Abstract: The flow meter (10), particularly useful in monitoring flow in semiconductor manufacturing operations, measures mass flow rate of fluids and is fabricated by providing spaced webs (16) deposited on a silicon substrate (11) and fluid flow grooves (13) etched across a substrate surface and extending under the spaced webs. The webs 16 include a low thermal conductivity layer deposited in spaced aligned portions of the substrate and electrically resistive pathways deposited on the layer portions (61). The webs act as temperature sensors and/or heaters. Heat is added to the flowing fluid and a differential temperature is measured on a bridge circuit as is known in the art to measure flow rate.

Abstract: The invention is a system for controlling the mass flow rates of vapor and carrier gas in a flowing fluid mixture. A regulated flow of carrier gas is divided so that a fraction of the flow passes through a vaporizer to pick up the vapor while the balance bypasses the vaporizer. The streams are then recombined and the resulting mixture is passed through a dew point detector which gives an output signal which varies according to variations in the mass ratio of the vapor to the carrier gas. A controller responds to the detector signal to generate a control signal which modulates a valve to vary the fraction of the carrier gas passing through the vaporizer, thereby influencing the mass rate at which the vapor is introduced. The feedback control from the dew point detector to the valve is adapted to regulate the dew point, and thereby the mass ratio of vapor to carrier.

Abstract: A mass flow sensor system for measuring the flow rate of a fluid in a sensing tube at diverse angular attitudes. Output signal distortion is minimized by neutralizing the effects of convection forces. The sensing tube is formed as a by-pass coupled to a fluid conduit and includes a loop in the shape of a single-turn helix. Circulation of the fluid through the loop cancels gravity-induced convection forces caused by temperature gradients and significantly reduces sensitivity to attitude change. Heating and temperature-sensing resistor coils are wound around the outer surface of the looped portion of the tube. The heater increases the tube temperature above that of the entering fluid, and the temperature difference between the temperature sensors, corresponding to rate of mass flow, is detected as a voltage output signal generated in an associated bridge circuit.

Abstract: A mass flow sensor system for measuring the flow rate of a fluid in a sensing tube at diverse angular attitudes. Output signal distortion is minimized by neutralizing the effects of convection forces. The sensing tube is formed as a by-pass coupled to a fluid conduit and includes a loop in the shape of a single-turn helix. Circulation of the fluid through the loop cancels gravity-induced convection forces caused by temperature gradients and significantly reduces sensitivity to attitude change. A center-tapped temperature-sensitive resistor coil is wound around the outer surface of the loop. The coil is heated, and the temperature differential between the ends of the coil, corresponding to rate of mass flow, is detected as a voltage output signal generated in an associated bridge circuit.

Abstract: Apparatus and method for obtaining a controlled gas mixture of predetermined proportionality using a temperature dependent permeation tube or like source for the addition of a small amount of a constituent gas in a higher flow rate carrier gas. A thermistor having a negative coefficient of resistance is associated with the permeation source and electrically connected to a flow controller for the carrier gas to automatically regulate the flow rate of the carrier gas in accordance with temperature variation of the permeation source.