Patent ID: 7401510
Filing Date: 2008-07-22
Classification: G01F

Abstract:
1. A hot-wire airflow meter for measuring airflow rate, comprising: a heat-generating resistor for a heating resistor type airflow meter; a resistance temperature detector for air temperature compensation; a current source that determines the ratio of currents that flow through said heat-generating resistor and said resistance temperature detector; and a current-detecting resistor for indirectly detecting the current that flows through said heat-generating resistor, wherein said current source comprises at least a current mirror circuit and an operational amplifier, said current mirror circuit comprising first, second, and third transistors connected in parallel, wherein said first transistor and said heat-generating resistor are connected in series, said second transistor and said resistance temperature detector for air temperature compensation are connected in series, and said third transistor and said current-detecting resistor are connected in series, wherein a voltage between said heat-generating resistor and said first transistor and a voltage between said resistance temperature detector for air temperature compensation and said second transistor are input to said operational amplifier, and wherein said first to third transistors are controlled by an output of said operational amplifier such that the current that flows through each of said resistors is controlled to maintain a predetermined ratio.