Non-obvious Problems in Clark Electrode Application at Elevated Temperature and Ways of Their Elimination
Figure 7
The proposed mechanism of gas bubbles formation in the electrolyte at periodic heating/cooling of the oxygen sensor (diffusion fluxes of gases are shown by arrows): (a) is initial state of the system at room temperature, (b) is rapid heating of the incubation medium, (c) is heating of the oxygen sensor after thermostabilization of the incubation medium, and (d) is cooling of the systems up to room temperature after work. (1) is the incubation medium, (2) is membrane, (3) is sensor electrolyte, and (4) is gas bubble. The main reason for the formation of bubbles (4) is supersaturation of the electrolyte (3) of the oxygen sensor during the heating (b, c) with insufficient rate of gas exchange with a medium (1) limited by a permeability of membrane (2). At the same time, even the low permeability of the membrane allows gases to return into the electrolyte from the medium under cooling (d). For this reason, bubbles are not dissolved completely under cooling.
