CARBON DIOXIDE MEASUREMENT - A CONTINUOUS CONDUCTIMETRIC METHOD

An instrument is described that continuously measures the carbon dioxide concentration in air with an accuracy suitable for field profile studies. The lag coefficient of the instrument is 20 sec. Air is passed continuously over deionized water counter-flowing in an absorption tube and the electrical conductivity of the water is measured before recycling it through a column of mixed bed deionizing resin. The output of the apparatus has a positive temperature coefficient, the main effect being on the electrical conductivity of the solution. When measuring differences in carbon dioxide concentration the temperature coefficient is 6%/°C and is independent of the absolute carbon dioxide concentration. The instrument was designed for continuous multi-channel operation as required in field studies of carbon dioxide profiles but is also suitable for leaf chamber experiments. © 1968.