Abstract: In a humidity measuring part a thermistor or similar temperature sensing element is used, as a humidity sensing element, in a heated state and an electric signal of humidity is obtained as a function of absolute humidity proportional to the water content of the atmosphere in a constant temperature and humidity bath through utilization of a change in the thermal conductivity of moist air. The absolute humidity signal and an absolute humidity set value or a set value of absolute humidity converted from a relative humidity set value through use of a temperature set value are compared, and a humidity control signal is produced in accordance with the result of this comparison. A forced humidifying signal is generated upon turning ON of the power supply, and the generation of this signal is stopped upon occurrence of the humidity control signal.

Abstract: A current is applied to a thermistor or like heat sensitive element having a temperature-resistance characteristic to heat the heat sensitive element up to a temperature above the open air temperature and the heat sensitive element is held in the open air. Since the resistance value of the heat sensitive element varies with the amount of water vapor contained in the open air, the change in the resistance value is detected, from which the humidity of the open air is obtained. By temperature compensation, direct reading of absolute or relative humidity is made possible.

Abstract: A method is described of making a catalytic combustion type gas detector, the sensitivity of which to alcohol vapors and to tobacco fumes is decreased by utilizing a mixture of powders. The mixed powders is composed of at least one metal oxide selected from TiO.sub.2, ZrO.sub.2, Y.sub.2 O.sub.3, HfO.sub.2, CeO.sub.2, La.sub.2 O.sub.3, NiO Cr.sub.2 O.sub.3 and a substance which presents an N-type semiconductor characteristic by gas adsorption. The mixture is coated directly on a wire coil of Pt or the like and a current is applied to the metal wire coil in an oxidizing atmosphere to sinter the coated mixed powder thereon.