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

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32 InPro 6800 Series O
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
A
measuring solution
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 ensure
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 elec-
trode.

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
Sensor 12/25 mm
2
polarization
voltage
anode
electrolyte
insulator
cathode
membrane
© 02 / 17 Mettler-Toledo GmbH
Printed in Switzerland