Measuring and testing – Volume or rate of flow – Thermal type
Patent
1989-12-05
1992-10-20
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Thermal type
7320414, 731182, G01F 168
Patent
active
051560461
ABSTRACT:
A thermal flow sensor of a switching control type for measuring the flow rate of intake air of an internal combustion engine comprises a bridge circuit including temperature sensing resistors, a differential amplification circuit, a pulse generating circuit, a power supply control circuit and a resonance preventing circuit. The amplification circuit amplifying the output from the bridge circuit. The pulse generating circuit receives the output from the amplification circuit and generates a pulse train which has a time ratio corresponding to the output level of the amplification circuit. The power supply control means comprises a switching transistor which is turned on and off by the pulse train from the pulse generating circuit and a smoothing circuit which makes the output from the transistor continuous and supplies the continuous voltage to the bridge circuit. The resonance preventing circuit comprises a phase lag compensation circuit including a resistor and a capacitor connected in series between a differential amplifier of the amplification circuit, or a variable DC unbalanced voltage generator including a V/I converter which converts the voltage received from the bridge circuit to a current corresponding to the level of the received voltage and a resistor which converts the current output from the V/I converter to a voltage and outputs a variable DC unbalanced voltage thereacross, whereby the resonance phenomenon in the full range of the flow rate is prevented.
REFERENCES:
patent: 4934188 (1990-06-01), Tanimoto et al.
"An Integrated flow sensor with pulse-modulated output" by Stemme in Transducers 87 pp. 364-367.
Sauer "Hot Wire Air Mass Meter" SAE Technical Paper Series 800468 Feb. 1980.
Bessho Mikio
Tanimoto Koji
Goldstein Herbert
Mitsubishi Denki & Kabushiki Kaisha
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