Oxygen sensing device

An oxygen sensor, comprising:

• not more than two electrochemical cells;
• wherein one of said cells comprises a first oxygen pump cell, disposed within a first substrate, further comprising:
• a first, negative electrode and a second, positive electrode, with a first communication zone therebetween, said first electrode being exposed to exhaust gas, said second electrode being exposed to a heat source;
• and wherein said first pump cell comprises a gas-diffusion limiting characteristic;
• wherein the other of said cells comprises a second oxygen pump cell, physically isolated from said first oxygen pump cell and disposed within said first substrate or a second substrate, and further comprising:
• a third electrode and a fourth electrode, with a second communication zone therebetween, said third electrode being exposed to exhaust gas, said fourth electrode being exposed to said heat source;
• a gas chamber, isolated from exhaust gases and connecting said second, positive electrode of said first pump cell and said fourth electrode of said second pump cell;
• and
• an electrical circuit for measuring an air-to-fuel ratio within said exhaust gas incident to said first and third electrodes and for controlling the current of the second pump cell.

An oxygen sensor, comprising:

• not more than two electrochemical cells;
• wherein one of said cells comprises a first oxygen pump cell further comprising:
• a first and a second electrode, with a first communication zone therebetween, said first electrode being exposed to exhaust gas, said second electrode being exposed to a heat source, and wherein said first pump cell comprises a gas-diffusion limiting characteristic;
• wherein the other of said cells comprises a second oxygen pump cell, capable of operating at opposite polarity from said first oxygen pump cell and physically isolated from said first oxygen pump cell, said second oxygen pump cell further comprising:
• a third and a fourth electrode, with a second communication zone therebetween, said third electrode being exposed to exhaust gas, and said fourth electrode being exposed to said heat source, and wherein said second pump cell comprises a gas-diffusion limiting characteristic;
• and
• an electrical circuit for measuring an air-to-fuel ratio within the exhaust gas incident to said first and third electrodes, wherein the electrical circuit both identifies a current limiting pump and measures a voltage difference at constant current or a current difference at constant voltage between said first and second oxygen pump cells.