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:
Mar. 19, 2002
Filed:
Jun. 30, 1999
Ryo Ando, Bolton, GB;
Masuo Akamatsu, Hitachinaka, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
In a ratiometric output type air flow meter with a heat generating resistor, a ratiometric circuit is provided with a divider circuit which is constituted by invariable resistors and divides an external reference voltage Vref and a multiplier circuit. The invariable resistor is grounded, via the invariable resistor. To one of input terminals of the multiplier circuit an output signal V of an operational amplifier is inputted, to the other input terminal of the multiplier circuit voltage Vex divided by the invariable resistors is inputted, and the output signal Vout of the multiplier circuit is outputted to an engine control unit. A correction use resistor is connected at the junction of the invariable resistor and a current detection resistor, and is grounded via a ground wiring resistance. Thus the voltage drop Vg caused by the ground wiring is compensated by the correction use resistor, and the voltage (Vex−Vg) representing the input to the multiplier circuit is kept constant regardless to the magnitude of a heating current flowing through the heat generating resistor. Thereby, a ratiometric output and heat generating resistor type air flow meter which permits a highly accurate air flow rate measurement is realized without being affected by variation due to the heating current flowing through the heat generating resistor.