Patent ID: 8899103

Claim:
A thermal air flow meter including: a bypass that takes in part of intake air to be measured and allows the intake air to flow therethrough; a flow rate detection element that is disposed in the bypass and includes a heating resistor made up of an upstream heating resistor located upstream of the intake air and a downstream heating resistor located downstream of the intake air, and an intake-air temperature detection resistor that detects the intake air temperature; and a bridge circuit unit that incorporates a bridge circuit including the heating resistor and supplies a current to the heating resistor so that the heating resistor temperature is always set higher by a predetermined temperature than the intake air temperature detected by the intake-air temperature detection resistor; wherein the bridge circuit unit outputs an output signal based on a value of the current supplied to the heating resistor, in accordance with a flow rate of the intake air; the thermal air flow meter comprising: a differential amplifier unit that amplifies a voltage dependent on difference in temperature between the upstream heating resistor and the downstream heating resistor; and a subtraction processor that subtracts from the output signal a constant times output from the differential amplifier unit, and outputs a correction output signal.