Abstract: 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.

Abstract: 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.

Abstract: 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.