How the Sensor Works
The Vernier Dissolved Oxygen Probe is a Clark-type polarographic electrode that
senses the oxygen concentration in water and aqueous solutions. A platinum
cathode and a silver/silver chloride reference anode in KCl electrolyte are
separated from the sample by a gas-permeable plastic membrane.
A fixed voltage is applied to the platinum electrode. As oxygen diffuses through
the membrane to the cathode, it is reduced
1/2 O2 + H2O + 2e– → 2 OH–
The oxidation taking place at the reference electrode (anode) is
Ag + Cl– → AgCl + e–
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Accordingly, a current will flow that is proportional to the rate of diffusion of
oxygen, and in turn to the concentration of dissolved oxygen in the sample. This
current is converted to a proportional voltage, which is amplified and converted to
concentration by the software.