Heat wire type air flowrate measuring apparatus

Details Heat wire type air flowrate measuring apparatus Heat wire type air flowrate measuring apparatus

1985-05-02

1987-05-19

Goldstein, Herbert

Measuring and testing

Volume or rate of flow

Thermal type

731182, G01F 168

Patent

active

046657452

ABSTRACT:
An air flowrate measuring apparatus with a heat wire measures the flow rate of the air flowing through the intake pipe of an engine. The apparatus has a temperature sensitive element which has a specific temperature-resistance characteristic and is disposed in the intake pipe. Constant heating voltage is applied to this element in response to a start signal, thus heating the element. When the temperature of the element rises to a specified value, the application of the voltage is stopped. At the same time, a pulse signal whose width corresponds to the period of applying the voltage is generated. The signal is supplied to an interface circuit through a drive circuit driven by a reference voltage which has been also used to control the heating voltage. The interface circuit comprises two wave-shaping circuits. The first wave-shaping circuit has a filter means of a small integration time constant. The second wave-shaping circuit has a filter means whose integration time constant is large enough to remove noise from the input signal.

REFERENCES:
patent: 3803913 (1974-04-01), Tracer
patent: 3928800 (1975-12-01), Strenglein
patent: 4043195 (1977-08-01), Hunting
patent: 4334186 (1982-06-01), Sasayama et al.
patent: 4565091 (1986-01-01), Ito et al.

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