Method and apparatus for correcting sensor output signal

US4140085A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Friedrich Rabus · Schwieberdingen, DE
• Hartmut Schweizer

Key dates

• Filing date: May 23, 1977
• Grant date: Feb 20, 1979
• Expiry date: May 23, 1997

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02D41/1479
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

A method and apparatus for use with fuel mixture preparation systems which employ an oxygen sensor in the exhaust line to determine the composition of the combustible mixture supplied to the engine and which adjust the mixture on the basis of the bi-valued signals from the sensor. In order to permit the use of these signals at lower than normal operating temperatures, where the internal resistance of the sensor is high and the output signal is skewed, the invention proposes generating a correction current which is passed through the sensor and which causes a voltage drop which symmetrizes the output voltage so that the two branches of the output signal always lie respectively above and below a fixed set-point voltage, thus permitting control loop processing. A circuit is also described which supplies the correcting current by comparison of the DC level of the output signal with the set-point value in a secondary feedback loop.