NEW FUNCTIONAL POSSIBILITIES FOR AMPEROMETRIC DISSOLVED-OXYGEN SENSORS

This papers deals with the study of new functional possibilities for amperometric sensors and problems in developing sensors capable of measuring oxygen transport characteristics (OTC) in liquids. The development of such sensors is carried out on the basis of a proposed scheme which differs from the Clark electrode in that the liquid to be analyzed is held on the external surface of the gas-permeable membrane. The functional possibilities of these sensors were studied by analysis of a three-layer dynamic model and by experimental investigations. It is demonstrated that these sensors may be applied in three areas: partial oxygen pressure measurement; the measurement of oxygen transport characteristics, such as: dissolved oxygen concentration, oxygen specific flow in liquid, its coefficients of solubility, permeability and diffusion in liquid; a combination of these. From this model conditions were formulated for choosing from a range of elementary parameters, to ensure the correct functioning of amperometric sensors in each of the above applications, with the required degree of measurement accuracy. An analysis of sensor behaviour was carried out, based on a model of diffusion-kinetic processes, permitting the explanation of the nature of systematic errors in sensor operation occurring in each of the application areas/modes mentioned. This model was also used for developing the algorithm for calculating the oxygen diffusion coefficient from the dynamic curve. The results of these theoretical investigations were confirmed satisfactorily by experimental investigations into the design of amperometric sensors.