Abstract: In order to provide a gas concentration measurement apparatus that suppresses any change in the temperature of an optical fiber, and also makes it difficult for any effects to appear in the measurement accuracy due to air from the surrounding environment penetrating the optical path of the measurement light while using only a simple structure and without causing any excessive energy consumption there are provided a first sealing component provided between an incident surface of a gas cell and a first end surface that is formed at a periphery of an emission aperture of a light-emitting unit so as to enclose the periphery of the emission aperture, and a second sealing component provided between an emission surface of the gas cell and a second end surface that is formed at a periphery of an incident aperture of a light-receiving unit so as to enclose the periphery of the incident aperture.

Abstract: This invention is to distinguish a position of a measurement cell without using a position sensor that is an electric component, and comprises a cell switching mechanism that switches a measurement position where the measurement cell is located on an optical path and an evacuating position where the measurement cell is evacuated from the optical path so as to make a first moving speed from the measurement position to the evacuating position different from a second moving speed from the evacuating position to the measurement position, and a distinguishing mechanism that detects speed information relating to the first moving speed and the second moving speed by the use of a measurement light and distinguishes the measurement position and the evacuating position.

Abstract: This invention is to distinguish a position of a measurement cell without using a position sensor that is an electric component, and comprises a cell switching mechanism that switches a measurement position where the measurement cell is located on an optical path and an evacuating position where the measurement cell is evacuated from the optical path so as to make a first moving speed from the measurement position to the evacuating position different from a second moving speed from the evacuating position to the measurement position, and a distinguishing mechanism that detects speed information relating to the first moving speed and the second moving speed by the use of a measurement light and distinguishes the measurement position and the evacuating position.