A Zirconia-Based Lean Air-Fuel Ratio Sensor

An experimental sensor has been developed to indicate the air-fuel ratio of an engine operating on lean mixtures. Stabilized zirconia doped with iron was used as the sensor electrolyte. These sensors are internally temperature compensated, eliminating the need for additional temperature sensing or electronics.

Sensor output is responsive to exhaust oxygen content, but is independent of exhaust temperatures above 450°C at 18:1. Addition of iron increased uniformity of output among sensors.