Abstract: An air flow detecting element is located in the air flow to be measured. This air flow detecting element comprises a heater made of resistant material having a positive temperature coefficient and wound around a first heat resistant frame, a first heat sensitive element wound around the first frame together with the heater and made of resistant material having a positive temperature coefficient and receiving heat from the heater, and a second heat sensitive element wound around a second heat resistant frame and made of resistant material having a positive temperature coefficient, and serving to measure the temperature of the air. A bridge circuit comprises a series circuit consisting of the heater and fixed resistances connected in series with each other, and a series circuit consisting of the first and second heat sensitive elements connected in series with each other. Potential differences at the output terminal of this bridge circuit are compared by an OP amplifier.

Abstract: Disposed in an intake pipe of an engine is a temperature-sensitive element formed of a resistance element whose resistance value varies with temperature. A heating current is supplied to the temperature-sensitive element through a transistor. The voltage of the heating current is set by a constant-voltage circuit. The temperature of the temperature-sensitive element is compared with a reference temperature of an auxiliary temperature-sensitive element. When the temperature of the temperature-sensitive element is increased to a predetermined level, an output signal is delivered from a comparator. A flip-flop circuit is reset by the output signal from the comparator, and is set by a start pulse signal. When the flip-flop circuit is set, the transistor is turned on, allowing the heating current to be supplied to the temperature-sensitive element.

Abstract: In a method for correcting the controlled variable of an engine according to the present invention, the quantity of suction air is measured by means of a thermal type flowmeter. The magnitude of pulsation of the suction air is obtained on the basis of the differential or variation of the measured section air quantity. At the same time, a coefficient representing the susceptibility to the pulsation which depends on the layout of the thermal type flowmeter and the like and the engine speed is calculated. A final correction for correcting the controlled variable is obtained on the basis of the magnitude of the pulsation and the coefficient representing the susceptibility.