Mks Instruments, Inc.

Aceinna, Inc.

Thomas O Maginnis

Yang Zhao

Yongyao Cai

Zhengxin Zhao

Nan Jou Pern

Wilfred J Baxter, Jr

The present invention provides a MEMS thermal flow sensor or meter for measuring the flow rate of a fluid without need for calibration of the flow sensor for that particular fluid. A response curve is determined by plotting the sensor output voltage against the volume flow rate divided by fluid thermal diffusivity for a calibration fluid of known thermal diffusivity, and storing response curve data in memory. A conversion factor is employed to provide a measure of correct flow rate of an unknown fluid. This conversion factor is derived from the ratio of the thermal time constant of the calibration fluid to the thermal time constant of the measured fluid, the time constants being measured at zero flow. These time constants are stored in memory. This conversion factor in conjunction with the response curve data is utilized by the processor to produce the correct flow rate. The invention also encompasses a method for measuring fluid flow rate of fluids of differing properties without necessity of a separate flow calibration for each fluid.

MEMS thermal flow sensor with compensation for fluid composition

A thermal mass flow sensor having superior sensitivity and response time includes a flow sensor tube defining an interior channel for fluid flow between input and output ends, a heating element in thermal communication with a portion of the flow sensor tube for heating a fluid flowing through the tube, a pair of spatially compact thermal sensors located at the upstream and downstream ends of the heating element for sensing the temperature of the fluid flowing through the tube at their respective locations and providing a signal representative of the fluid temperature at those locations, and a pair of thermal grounding members on the flow sensor tube, yet positioned at specified locations substantially beyond the heated portion of the tube, for establishing reference temperatures for the fluid flowing therethrough at those locations.

Thermal mass flow sensor with improved sensitivity and response time

A thermal mass flow sensor in which heat transfer to and from a fluid flowing through a sensor conduit is optimized by establishing a symmetrical triangular temperature distribution along a heated length of the sensor conduit. The sensor conduit is heated by a pair of distributed heat sources and a concentrated heat source located between the distributed heat sources. The heater density of the sensor conduit increases linearly from the outer ends of the distributed heat sources towards the center of the heated length of the sensor conduit, and spikes to a substantially greater value at a point corresponding to the centrally located concentrated heat source. The temperature distribution function along the flow sensor tube is a substantially symmetric triangular function.

Constant temperature gradient differential thermal mass flow sensor

The disclosed flowmeter includes a sensor tube and a heater. The sensor tube defines an input end, an output end, and an interior channel extending from the input end to the output end and permits fluid to flow from the input end through the channel to the output end. The heater includes a first end and a second end, and the heater establishes a non-uniform heater density function between the first and second ends. The heater is disposed proximal to the sensor tube for heating the tube.

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Dracut, MA, United States of America

Thomas O Maginnis