Zirconia Oxygen Sensor - An Equivalent Circuit Model

The zirconia exhaust gas oxygen sensor is a key component in closed loop engine emissions control systems. An equivalent circuit model of the sensor is derived from fundamental electrochemical principles. In this model, sensor electrode resistance and capacitance are separated from the zirconia electrolyte resistance.

An important theoretical conclusion is that the resistances (electrode kinetics) of microscopic CO and O₂ voltage cells enter into the determination of sensor output voltage and its transient response. In addition, numerical examples are given to show how the equivalent circuit can be used to model both steady state and transient characteristics of sensors.