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Medical Definition of Clark electrode
1. An oxygen electrode consisting of the tip of a platinum wire exposed to a thin film of electrolyte covered by a plastic membrane permeable to oxygen but not to water or the electrolyte. When a certain voltage is applied, oxygen is destroyed at the platinum surface; the flow of current is then proportional to the rate at which oxygen can diffuse to the platinum surface from the gas or liquid sample outside the membrane, and is thus a measure of the oxygen pressure in the sample; commonly used to measure oxygen pressure in arterial blood samples. (05 Mar 2000)