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--- do_measurementprinciple [31/03/2015 13:31]
pieter [Membrane thickness and cathode area]
+++ do_measurementprinciple [31/03/2015 13:32]
pieter
@@ Line 32: / Line 32: @@
   * Teflon offers resistance to oxygen diffusion. Thus, at a given temperature and a fixed concentration of oxygen at the water-to-Teflon interface, the number of oxygen molecules arriving at the cathode per unit of time is inversely proportional to membrane thickness (D).
-//N////t//// = f [O////2//// x (1/D)]//
+**//N////t//// = f [O////2//// x (1/D)]//**
 From these relationships, it is evident that in order to have maximum sensitivity for the probe it is necessary to make the cathode area as large as is practical and to make the Teflon membrane as thin as is practical. The practical consideration for cathode size is its relationship to overall probe size, which usually is determined by where the probe must be placed. Membrane thickness must recognise desired response rate and rugged performance. Thin membranes provide quick response in addition to sensitivity because diffusion equilibrium is reached more quickly, but thicker membranes are tougher and will provide longer service.

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