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For effective operation of PEFC (Proton Exchange Fuel Cell), it is desired to measure hydrogen concentration in anode side gas stream. We have developed a linear Hydrogen Sensor, which comprises a pair of Pt supported carbon electrodes and a proton exchange membrane (PEM). The sensor has limited current sensing characteristics. The concentration of hydrogen supplied from the gas diffusing area at the anode side is measured by detecting the current of the selective hydrogen pumping. The carbon electrode deterioration occurred when little hydrogen existed in the sensing area. By controlling an applying voltage to the PEM electrodes when the pumping current is lowered to a certain limit, this issue has been solved; no deterioration occurred even after 2500 hours continuous operation under ambient atmospheric conditions. This sensor is suitable for anode side gas purge control of automotive hydrogen FC and for power management of reformed gas FC for home co-generation.

The oxygen sensor for automobiles is widely used for the exhaust gas control system by using a three way catalyst and constitutes a very important function part of combustion control system in the internal combustion engine. The air-fuel ratio is controlled at the stoichiometric point, where the best purification efficiency is obtained. Recently a wide range air-fuel ratio control system has been developed for the areas of lean burn combustion for fuel economy, low emissions at low temperature starts, and full power control at W.O.T. with rich burning. The UEGO (Universal Air-Fuel Ratio Heated Exhaust Gas Oxygen) sensor has been developed to meet the wide range of air-fuel ratio control. This UEGO sensor indicates output proportionally for all ranges of air-fuel ratio, unlike the conventional oxygen sensor which detects only the stoichiometric point.