Steady state mode oxygen sensor and method

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

• a solid electrochemical pump cell;
• a solid electrochemical sensor cell;
• an associated supporting structure which in combination with said pump and sensor cells defines an enclosed volume;
• a leak orifice for providing communication between said enclosed volume and the ambient environment so that when said enclosed volume is immersed in an ambient environment containing a partial pressure of oxygen there is a tendency for the partial pressure of oxygen inside said enclosed volume to equalize with the partial pressure of oxygen of the ambient environment;
• an external circuit means coupled to said pump cell to apply an electrical input to said pump cell and coupled to said sensor cell for measuring an electrical output generated by said sensor cell in response to said electrical input at said pump cell, said external circuit means including a control means to apply a current of sufficient magnitude as said electrical input to maintain a constant voltage across said sensor cell, and said external circuit means including sensing means for sensing the magnitude of said electrical input which is proportional to the percentage of oxygen in the ambient environment thus permitting said electrochemical apparatus to be used as a sensor of the percentage of oxygen;
• said pump and sensor cells being formed of platelets of solid ionic conductors capable of conducting oxygen ions, and including two electrode layers attached to opposing faces of each of said platelets, and lead wire attached to each of said electrodes for coupling said first and second circuit means to said pump and sensor cells, respectively.