The Pd-doped SnO2 thin film detector for gaseous components has been developed, whose detection is based on the fact that the adsorption and desorption of gases cause the remarkable change in electrical resistivity of the semiconductor. This property of SnO2 film is applicable to the preferential detector for gaseous components, especially ethanol gas. SnO2 thin film was prepared on the polished ferrite substrate which SiO was precoated. Both the preparation and the precoating were done by vacuum deposition. Subsequently the oxidation for SnO2 film in air was done at 500–550 °C for 30–60 min. The rise rate and fall rate of temperature were 2.5 and 1.7 °C/min, respectively. The thickness of SnO2 film was about 0.3–0.35 μm.

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In this paper, we monitored the electromagnetic waves generated by human activity. We investigated a monitoring system that used the bioelectric potential of a plant. Four subjects walked on the spot at a distance of 60 cm from a rubber tree and we measured the variation in the bioelectric potential of the tree produced by the stepping motion. The results confirmed that the electromagnetic waves generated by a person walking on the spot produced a measurable response in the bioelectric potential of a plant. It was also found that this variation in the bioelectric potential varied in synchrony with the subject's walking pace.

Thick film gas sensor of tin oxide based materials has been developed by screen printing method, and its sensing characteristics have been examined for some gases. To perform the method, tin oxide fine power with the size about 0.5 μm in diameter was prepared through the fine crystallization in liquid phase, and was mixed with glass frits as a binder and palladium or platinum as a catalyst. This mixed material is used as the paste. With the screen printing method using the paste, the mass production and the sufficient mechanical strength of the sensor can be achieved. The gas sensor of tin oxide incorporated with palladium black as the catalyst shows an excellent selective detection for ethanol and hydrogen gases at the specimen temperature of 250 °C. And the platinum black-doped tin oxide sensor has also a high sensitivity to both gases at the temperature over 350 °C.