Measuring and testing – Volume or rate of flow – Thermal type
Patent
1981-11-23
1983-11-29
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Thermal type
G01F 162
Patent
active
044174713
ABSTRACT:
A first temperature dependent resistor and a second temperature dependent resistor are disposed within a single gas passage defined by a branch pipe extending into a conduit for a gas whose flow rate is to be measured. An electric heater is located between these temperature dependent resistors and is heated for the purpose of measurement of the flow rate of the gas. A first reference resistor and a second reference resistor constitute a bridge circuit together with the first and second temperature dependent resistors, and the difference between the potentials at the terminals of the bridge circuit is amplified by a first differential amplifier circuit. The difference between the output voltage of the first differential amplifier circuit and a predetermined reference voltage is then amplified by a second differential amplifier circuit. The output of the second differential amplifier circuit is amplified by a power amplifier, and the output of the power amplifier is used to control the current or voltage supplied to the electric heater.
REFERENCES:
patent: 3405708 (1968-10-01), Webster, Jr.
patent: 3648518 (1972-03-01), Hans et al.
patent: 3975951 (1976-08-01), Kohama et al.
patent: 4067233 (1978-01-01), Obayashi et al.
patent: 4080821 (1978-03-01), Johnston
patent: 4332165 (1982-06-01), Kawai
Egami Tsuneyuki
Kawai Hisasi
Kohama Tokio
Obayashi Hideki
Goldstein Herbert
Nippon Soken Inc.
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