Circuit for a NOx measurement sensor

US6300753A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Tim Walde · Regensburg, DE
• Eric Chemisky · Haar, DE

Key dates

• Filing date: Feb 24, 2000
• Grant date: Oct 9, 2001
• Expiry date: Feb 24, 2020

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N27/4065
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A circuit for a NOx concentration sensor includes two connected measurement cells disposed in a solid-state electrolyte, a first circuit configuration that, by tapping off a first Nernst voltage (first reference variable), establishes in the cell an oxygen concentration that differs from that in a measured gas, a second circuit configuration that, by tapping off a second Nernst voltage (second reference variable), establishes in the cell an oxygen concentration that differs from that in the first cell, a third circuit configuration that, by tapping off a third Nernst voltage (third reference variable), drives a pump current of oxygen ions that originate from NOx, out of the second cell, a conditioning circuit, and a digital controller. The Nernst voltage is fed to the controller through the conditioning circuit, which shifts and amplifies the voltage such that the reference variable lies in a range around the control point of the controller, and a reference potential of a conditioned Nernst voltage equals that of the controller. The Nernst voltages, being previously preprocessed by the conditioning circuit, are used as a reference variable for regulating the oxygen ion pump current…