Product Description; General Information; Principle - Mettler Toledo InPro 6850i Bedienungsanleitung

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Product description

3.1

General information

The oxygen sensor series InPro 6850i / 6900i /
6950i with integrated temperature probe are used for
measurement of oxygen at low and medium
concentrations.
The sensors are sterilizable, and in the majority of
cases autoclavable too and they are compatible with
CIP (cleaning in place).
InPro 6xxxi sensors with ISM functionality offer
Plug and Measure as well as enhanced diagnostics
features.
3.2

Principle

Amperometric oxygen sensors:
The amperometric oxygen sensors of METTLER
TOLEDO base all on the same mearuring principle
according to Clark. However different series are of-
fered, which clearly differ in the number and arrange-
ment of their electrodes and thus in their specifica-
tions:
• The measurement system of the InPro sensors
consists of a working electrode (cathode), a
counter electrode (anode), a reference electrode
and a guard ring electrode. The measurement
system is separated from the process medium by
an oxygen permeable membrane.
• The measuring technique in principle is alike with
all sensors.
• The transmitter supplies a constant voltage be-
tween cathode and anode.
• The electrolyte creates a conductive connection
between the electrodes.
• The oxygen molecules migrate from the measure-
ment medium through the membrane to the
cathode to which the voltage is supplied and are
reduced. At the same time, oxidation takes place
at the anode.
• This causes a current to flow between the anode
and cathode which is directly proportional to the
partial pressure of oxygen (pO
medium. With digital ISM sensors, the sensor it-
self converts the current into oxygen concentration
and communicates the value to the transmitter.
• The guard ring electrode of the InPro 6900i and
6950i built into the sensor reduces the oxygen
that migrates to the side of the cathode and can
distort the measurement. The guard ring electrode
therefore enables traces of oxygen to be precisely
determined at even the lowest concentrations.
Note: Please refer to "Section 10 – Theory of the po-
larographic sensor" for further information.
InPro 6850i, 6900i, 6950i
52 206 349
InPro 6850i / 6900i / 6950i O Sensor 12 / 25 mm
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) in the process
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© 02 / 09 Mettler-Toledo AG
Printed in Switzerland