Opto‐Chemical CO2 Sensors

Summary

Opto‐chemical sensors are usually very sensitive, robust, fast, and inexpensive and can be easily miniaturized. A fibre‐optic fibre transfers light into the sensor capsule with the fluorescent dye. Opto‐chemical CO₂ sensors show an excellent long‐term stability without the need for the commonly required periodic calibrations. Detector tubes are thin, graduated glass tubes containing a chemically sensitive substance that reacts specifically with the gas or vapour to be measured, resulting in a clearly visible change of its colour when exposed to the gas in question. This chapter shows the general set‐up of a fibre‐optic sensor. In general, light guided in an optical fibre can interact with an external measurand in two ways: extrinsic sensors and intrinsic sensors. The most widely used fluorescence dyes to sense carbon dioxide on the basis of the Severinghaus effect use ion pairs between an pH‐sensitive indicator anion and a quaternary ammonium cation.