Measurement Technique and its Application to Trace Components of Atmospheric Gas

From early on, HORIBA has been developing and adopting various measurement techniques that are ideal for measuring trace atmospheric gas, as in the following examples. To measure carbon monoxide (CO), a non-dispersive infrared absorption method is used. To measure Ozone (O3), an ultraviolet absorption method is used. For nitrogen oxides (NOX), chemiluminescence. For sulfur dioxide (SO2), ultraviolet fluorescence. For hydrocarbons (HC), a flame ionization method is used, and so on. In addition, HORIBA has developed a fluid modulation method, which is a method to measure gas concentrations by amplifying the difference of two signals coming from a measurement cell into which the sample gas and a reference gas are alternately introduced with a constant time interval, and has achieved absolute zero-point stability with all except SO2 analyzer. In the case of CO measurement, HORIBA has succeeded in reducing the infl uence of moisture by using an interference compensation detector. In the case of O3 and SO2 measurement with a light source, in which light intensity variation over time is not negligible, it compensates for the infl uence by monitoring the light source intensity. Also, a highly productive measurement system has been developed with which it is possible to measure multiple gas components with a single detector by combining a catalyzer or convertor unit and the three-phase fluid modulation method (introducing three types of gas alternately), such as, NOX that can measure NO and NO2 at the same time and HC that can simultaneously measure methane (CH4) and nonmethane (non-CH4). These various techniques for making comprehensive measurement systems have been adopted also to measure trace quantities of ammonium (NH3) or hydrogen sulfi de (H2S) inside the clean room.

(Same content in Japanese is in Readout No.31-Japanese edition-.)

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