GAS METER

Japanese Patent JP3186089

B2

PURPOSE: To improve the sensitivity of a thermal flow sensor in a very small flow rate region by switching the gain of a detection circuit incorporating the flow sensor in accordance with a preset flow rate threshold.
CONSTITUTION: A switch S2 is periodically closed for a short time by means of a microcomputer 10 so that resistors RD and RU for detecting liquid temperature can be conducted and heated. As a result, a thermal flow sensor 3 is periodically actuated for the short time and detects the velocity of a flow. Resistors R8 and R9 are feedback resistors connected to an operational amplifier A3 and their gains become smaller when a gain change-over switch S2 is closed. Therefore, the flow rate versus output characteristic, namely, flow rate sensitivity characteristic of a detection circuit becomes such that the sensitivity becomes lower when the switch S2 is closed and higher when the switch S2 is opened. The switch S2 is kept opened until the output of an A/D conversion circuit 9 exceeds a preset flow rate threshold. When the output exceeds the threshold, the switch S2 is closed and indicates the same flow rate sensitivity characteristic as the conventional detection sensitivity. In addition, the switch S2 is operated by means of a sensitivity switching signal from the microcomputer 10.

JP2014232015	FLOW SENSOR
JP4453304	Gas shutoff device
JP3205469	FLOW RATE DATA STORING UNIT

Yasuo Sato
Toshihiko Ito
Yasushi Mizukoshi

JP14643291A

July 11, 2001

June 19, 1991

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Toho Gas Co., Ltd.
Aichi Clock Electric Co., Ltd.
Toyo Gas Meter Co., Ltd.

G01F1/00; G01F1/696; G01F1/20; G01F7/00; G01F15/075; (IPC1-7): G01F1/20; G01F7/00

JP396817A
JP375523A

Yoshimichi Hasegawa

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