Thermal mass flow sensor with improved sensitivity and response time
First Claim
1. A thermal mass flow sensor, comprising:
- a) a flow sensor tube defining an input end, an output end, and an interior channel for fluid flow between the input and output ends;
b) a heating element in thermal communication with a portion of the flow sensor tube for heating a fluid flowing therethrough, the heating element being made of a material having a low temperature coefficient of resistance and providing a heat density distribution along the portion of the flow sensor tube;
c) a pair of thermal sensors, separate from the heating element, in thermal communication with the flow sensor tube, each sensor located at a respective end of the heating element on the flow sensor tube, for sensing the temperature of the fluid flowing through the flow sensor tube and providing a signal representative of the fluid temperature at the respective thermal sensor locations; and
d) a pair of thermal grounding members on the flow sensor tube spaced a predetermined distance from the ends of the heating element for establishing respective inlet and outlet reference temperatures for the fluid flowing through the flow sensor tube substantially independently of the heat density distribution provided by the heating element along the portion of the flow sensor tube.
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Accused Products
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.
42 Citations
8 Claims
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1. A thermal mass flow sensor, comprising:
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a) a flow sensor tube defining an input end, an output end, and an interior channel for fluid flow between the input and output ends;
b) a heating element in thermal communication with a portion of the flow sensor tube for heating a fluid flowing therethrough, the heating element being made of a material having a low temperature coefficient of resistance and providing a heat density distribution along the portion of the flow sensor tube;
c) a pair of thermal sensors, separate from the heating element, in thermal communication with the flow sensor tube, each sensor located at a respective end of the heating element on the flow sensor tube, for sensing the temperature of the fluid flowing through the flow sensor tube and providing a signal representative of the fluid temperature at the respective thermal sensor locations; and
d) a pair of thermal grounding members on the flow sensor tube spaced a predetermined distance from the ends of the heating element for establishing respective inlet and outlet reference temperatures for the fluid flowing through the flow sensor tube substantially independently of the heat density distribution provided by the heating element along the portion of the flow sensor tube. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A thermal mass flow sensor, comprising:
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a) a flow sensor tube defining an input end, an output end, and an interior channel for fluid flow between the input and output ends;
b) a heater arrangement, in thermal communication with a portion of the flow sensor tube that heats a fluid flowing therethrough so as to provide a heat density distribution along the portion of the flow sensor tube;
c) a pair of thermal sensors, separate from the heater means, in thermal communication with the flow sensor tube, each sensor located at a respective end of the heater means on the flow sensor tube, for sensing the temperature of the fluid flowing through the flow sensor tube and providing a signal representative of the fluid temperature at the respective thermal sensor locations; and
d) a pair of thermal grounding members on the flow sensor tube spaced a predetermined distance from the ends of the heater means for establishing respective inlet and outlet reference temperatures for the fluid flowing through the flow sensor tube substantially independently of the heat density distribution provided by the heater means along the portion of the flow sensor tube.
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Specification