High sensitivity phase-transformation-based oxygen sensors for proportional control

摘要

Described are a sensing method and an oxygen sensor for detecting a change of oxygen partial pressure in an ambient atmosphere through a change of a measurable physical property of a sensing material. The sensor (10) includes a sensing material (12) selected from metal or its oxides which, when at an elevated temperature and exposed to a gas containing a changing partial pressures of oxygen, is capable of changing from one metal or metal oxide phase to another such oxide phase and vice versa. A typical example is the CoO/Co3O4 system. Associated with such phase change is a change in a measurable physical property of the material. The sensor also includes heating means (19), connectable to a power source, maintaining a temperature gradient across the sensing material since it is critical that the sensing material exist in at least two phases during active sensing. An output signal is furnished in response to the change in a physical property, like electrical resistance, of a portion of or of the entire material in response to change in oxygen partial pressure. <IMAGE>