Patent ID: 6134960
Filing Date: 2000-10-24
Classification: G01F

Abstract:
A thermal-type flow sensor including a plurality of heat generating portions implemented by heat-sensitive resistors disposed at positions upstream and downstream within a passage as viewed in a direction in which fluid flows through said passage, to thereby measure a flow rate or a flowing speed of said fluid on the basis of heat transfer phenomenon taking place between said heat generating portions and said fluid, comprising:heating current control means for controlling heating currents flowing through said heat-sensitive resistors so that temperatures of said plurality of heat generating portions increase by predetermined values relative to temperature of said fluid;means for determining difference between heating currents flowing through the heat generating portion located upstream and the heat generating portion located downstream in said plurality of heat generating portions; andmeans for detecting the flowing speed or said flow rate of said fluid on the basis of the difference between said heating currents,wherein the heating current flowing through said heat-sensitive resistor located upstream is set to be greater than the heating current flowing through said heat-sensitive resistor located downstream when said flow rate is zero.