The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 22, 1997
Filed:
Nov. 25, 1994
Ricoh Company, Ltd., Tokyo, JP;
Abstract
A heater-heat sensor type thermal flow sensor including a substrate installed in a fluid path, a channel formed on a part of the substrate; a bridge suspended over the channel; a heater constructed with an electric resistor formed on the bridge; a temperature sensor for measuring the temperature of the heater which is constructed with another electric resistor situated on the bridge and measuring the temperature of the heater; and a fluid temperature sensor constructed with still another electric resistor formed on a position of the substrate not thermally affected by the heater. There is a bridge circuit including the temperature sensor for measuring the temperature of the heater, the fluid temperature sensor, and first and second resistors both installed outside of the fluid path. A control circuit is provided to control the voltage applied to the heater in accordance with the output of the bridge circuit. The heater and the heat sensor are superposedly formed on the bridge through an interlayer insulating film in order to substantially eliminate the difference between the temperatures of the heater and heat sensor. A temperature compensating circuit is connected to the output stage of the control circuit.