a solid - state oxygen microsensor which measures the potential difference generated by two spaced apart electrodes deposited on a solid oxygen ion conducting electrolyte and located in a known and preferably constant temperature gradient in the same ambient atmosphere . output voltage of the sensor is proportional to the temperature gradient established across the electrodes and the unknown oxygen partial pressure of the ambient atmosphere . the solid - state oxygen microsensor is useful for application to systems such as combustion systems to maintain and improve combustion efficiency levels and exhaust gas cleanliness .