Measuring and testing – Volume or rate of flow – Thermal type
Patent
1979-11-27
1981-06-30
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Thermal type
G01F 168
Patent
active
042755905
ABSTRACT:
Voltages at the diagonal points of a bridge circuit are amplified in an AC differential manner and half-wave rectified, which bridge circuit is formed of reference resistors and temperature dependent resistors located in front and rear of an electric heater in a duct through which air to be measured flows. The half-wave rectified voltage is sampled and held in synchronism with a control pulse signal from an oscillation circuit so that the sampling and holding operation is performed substantially at the center of the period during which the half-wave rectified voltage is produced. The held voltage and a constant reference voltage are amplified in a DC differential manner and then applied to a power amplifier circuit which controls a supply voltage to the electric heater. The voltage to be applied to the bridge circuit is an intermittent voltage which is produced by a chopper circuit.
REFERENCES:
patent: 3975951 (1976-08-01), Kohama et al.
patent: 4067233 (1978-01-01), Obayashi et al.
patent: 4089214 (1978-05-01), Egami et al.
Egami Tsuneyuki
Kawai Hisasi
Kohama Tokio
Obayashi Hideki
Goldstein Herbert
Nippon Soken Inc.
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