Parameters Determining Current - Mettler Toledo InPro 6950 Serie Bedienungsanleitung

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Principle of the design of the InPro 6950
The InPro 6950 sensor is based on the Clark elec-
trode. However it also has a cathode ring (guard ring
electrode) and a reference electrode.
The guard ring electrode is connected to a separate
polarization voltage and hence consumes the oxygen
that is released from the electrolytes to the measure-
ment cathode.
The reference electrode is used as a reference point
to adjust the necessary polarization voltage between
the cathode and anode and hence creates stable
conditions within the sensor during measurement.
This guarantees exceptional signal stability in the
measurement system down to trace levels of oxygen.
Process Medium

10.3 Parameters determining current

The quantity of oxygen diffused in and the magnitude
of the electrode current are influenced by the follow-
ing parameters:
– Oxygen partial pressure of the solution
– Membrane material and thickness
– Size of cathode
– Polarization voltage
– Temperature
– Flow conditions in the solution
Fick's law gives the mathematical relationship
between these parameters:
l = k
I = Electrode current
k = Constant
D = Coefficient of diffusion of O
a = Solubility of O
A = Cathode surface
pO = Oxygen partial pressure in the solution
2
X = Thickness of gas-permeable membrane
InPro 6950
52 206 137 F
U
(Potentiostat)
D a
InPro 6950 Series O
U
A
O O
2 2
O
2
pO
A
2
x
in the membrane
2
in the membrane material
2
© 02 / 2023 METTLER TOLEDO
Sensor 12 mm
2
(Potentiostat)
Printed in Switzerland
Polarization
Voltage
Reference
Electrolyte
Insulator
Cathode (Pt)
Anode (Pt)
Guard
Membrane