Principle Of The Design Of An Oxygen Electrode; Parameters Determining Current - Mettler Toledo InPro 6800 Serie Instructions D'utilisation

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10.2 Principle of the design of an
oxygen electrode
There are two main types of oxygen electrodes:
– Electrodes without membrane
– Electrodes with gas-permeable membrane
(Clark Principle)
The membrane electrode according to Clark is today
most widely used. As compared to the electrode with-
out membrane it possesses the following advantages:
– Oxygen measurement in gases and solutions
– No mutual contamination of electrode and solution
– No or little dependency on flow
In the case of the Clark electrode, geometrical config-
uration is very important. In particular, the thickness of
the electrolyte film between the cathode and the mem-
brane must be within narrow tolerances so as to en-
sure good linearity and a low zero current (current in a
nitrogen atmosphere). The figure above exemplifies the
principle of the design of a Clark-type oxygen electrode.

10.3 Parameters determining current

The quantity of oxygen diffused in and the magnitude
of the electrode current are influenced by the following
parameters:
– Oxygen partial pressure of the solution
– Membrane material and thickness
– Size of cathode
– Polarization voltage
– Temperature
– Flow conditions in the solution
InPro 6800
52 200 953
InPro 6800 Series O
measuring solution
A
© 10/05 Mettler-Toledo GmbH
Sensor 12/25 mm
2
polarization
voltage
anode
electrolyte
insulator
cathode
membrane
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