Step function lean burn oxygen sensor

An electrochemical apparatus for making a measurement of oxygen partial pressure in an ambient environment including other gaseous materials, said electrochemical apparatus including:

• a single solid electrochemical pump cell formed of a platelet of solid ionic conductors capable of conducting oxygen ions and including two electrode layers attached to opposing faces of said platelet, and lead wires attached to each of said electrodes for providing electrical coupling to said pump cell;
• a leaky structure coupled to said electrochemical pump cell having an enclosed casing defining an enclosed volume and a leak orifice coupling the enclosed volume to the ambient;
• an external circuit means coupled to said pump cell for applying a current to said pump cell so that oxygen can be withdrawn from the enclosed volume thereby providing an electrical output indicative of oxygen partial pressure;
• said external circuit means including:
• a constant current source means coupled to said electrochemical pump cell thereby generating said electrical output wherein a voltage, V, is a function of the oxygen partial pressure;
• a first reference voltage means coupled to said constant current source means for producing a first step voltage output with the step occurring at a first output voltage related to a first oxygen partial pressure;
• a second reference voltage means coupled to said constant current means for producing a second step voltage output with the step occurring at a second output voltage related to a second oxygen partial pressure;
• an output means coupled to said first and second reference voltage means for generating a voltage step output having at least three voltage levels with steps occurring at said first and second partial pressure of oxygen thus indicating the relative magnitude of the oxygen partial pressure with respect to said first and second oxygen partial pressures.