AIR FLOWMETER

PURPOSE:To obtain the flowmeter for an automobile internal combustion engine which can perform stable, highly accurate measurement immediately after a power source is turned ON, by shorting a first resistor which is connected to a flow speed detecting resistor in series for a specified time period when the power source is turned ON, and adding a constant voltage to the connecting points. CONSTITUTION:A Wheatsone bridge circuit is constituted by a flow speed detecting part probe 1, a temperature compensating probe 2, a resistor 3, and a resistor 4. The constant voltage Vo is applied across the connecting point between the flow speed detecting part probe 1 and the temperature compensating probe 2 and the connecting point between the resistor 3 and the resistor 4. The outputs from connecting points are inputted to a differential amplifier 5. The output from the amplifier is inputted to the base of the transistor 6. Meanwhile, the output signal from a timer 8 which is operated by the output from an engine key switch 9 is inputted to the base of a switching transistor 10 which is connected to the resistor 3 in parallel. The constant voltage is applied to the positive terminal of the differential amplifier 5 from a constant voltage power source 12 through a diode 11.