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From the viewpoint of global environment and petroleum energy depletion problems, a hydrogen-based fuel cell is attracting people's attentions as a clean energy source. The object of the present paper is to summarize approaches for achieving high stability and high selectivity in developing hydrogen sensors that detect hydrogen gas, fuel of fuel cells. For gas detection principles, various systems including a semiconductor system exist. We are developing hydrogen sensors with thermal conductivity principle applied, in which the difference of gas thermal conductivity is utilized with adaptability in applications for fuel cell electric vehicles taken into account. When the environment in automobile applications is assumed, high selectivity to detect hydrogen alone is required because various gases such as water vapor and exhaust gas (methane, carbon monoxide, etc.) coexist. In particular, the thermal conductivity principle causes big errors at high temperature and high humidity.

A new oil pressure sensor has been developed utilizing iron base amorphous magnetic alloys. The sensor was composed of a cylindrical body with oil inlet, the amorphous magnetic alloy strip glued around the body and coils arranged to the alloy. The output behavior of the sensor was explained successfully by applying a rotation magnetization model. The characteristics of the developed sensor were as follows. Measurable pressure range; 0 to 20MPa. Operating temperature range; -30 to 100°C Inaccuracy; less than 2 %F.S. (F.S. means full scale) The durability tests like cyclic heating or pressure application demonstrated that the developed sensor is durable enough for automobile use.