Polarization Voltage; Temperature - Mettler Toledo InPro 6800 Serie Instructions D'utilisation

InPro 6800 Series O
Fick's law gives the mathematical relationship between
these parameters:
I = k • D • a • A •
I =
k =
D =
a =
A =
pO =
2
X =

10.4 Polarization voltage

The voltage between the anode and the cathode is so
selected that the oxygen is fully (> A, see polarogram)
reduced while other gases are unaffected (< D). The
ideal voltage for the Pt/Ag/AgCl system is between
–500 and –750 mV.
100
90
80
70
60
50
40
30
20
10
0
The polarization voltage should remain as constant as
possible. Besides a constant source of voltage the
following prerequisites must be met:
The electrical resistance of electrolyte film must not
exceed a particular value so as to avoid a voltage drop.
The anode must have a large surface so as to prevent
polarization of the anode by the electrode current.

10.5 Temperature

The temperature dependence of the current passing
through an oxygen electrode when referred to a
constant O
the properties of the gas-permeable membrane.
© 10/05 Mettler-Toledo GmbH
Printed in Switzerland
Sensor 12/25 mm
2
pO
electrode current
constant
coefficient of diffusion of O
solubility of O
cathode surface
oxygen partial pressure in the solution
thickness of gas-permeable membrane
Typical current voltage
curves in agitated
0.1 mol/l KCl
No. 1 Nitrogen
No. 2 21% Oxygen
No. 3 100% Oxygen
«A»
0.2 0.4 0.6
partial pressure is determined mainly by
2
2
X
in the membrane material
2
No. 3
No. 2
«D»
0.8 1.0
in the membrane
2
No. 1
1.2
– E (Volts)
InPro 6800
52 200 953
33