Patent ID: 7631555

Claim:
A thermal flowmeter of a fluid, comprising: a flow rate measuring element disposed in a fluid passage and including a heating resistor generating heat with supply of a current, a temperature compensation resistor for detecting a fluid temperature, a first temperature measuring resistor for measuring a temperature upstream of said heating resistor, and a second temperature measuring resistor for measuring a temperature downstream of said heating resistor, all of said resistors being formed on the same substrate; a temperature control circuit for controlling a temperature of said heating resistor; a casing supported to a wall surface of an intake pipe forming said fluid passage and supporting said flow rate measuring element; a temperature sensor for measuring a temperature in said casing; a computing unit for receiving signals corresponding to a fluid flow rate from said first and second temperature measuring resistors, performing correction depending on temperature by using said temperature sensor, and outputting the corrected result; and heating temperature control means causing a difference between the fluid temperature and the temperature of said heating resistor to be changed depending on the fluid temperature.