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Trace Oxygen Analyzer Operational Theory
Teledyne Analytical Instruments 5
Operational Theory
2.1 Introduction
The analyzer is composed of two subsystems:
1. Analysis Unit with Micro-Fuel Cell Sensor
2. Control Unit with Signal Processing, Display and Controls
The Analysis Unit is designed to accept the sample gas and direct it
to the sensitive surface of the Micro-Fuel Cell sensor. The Micro-Fuel
Cell is an electrochemical galvanic device that translates the amount of
oxygen present in the sample into an electrical current.
The Control Unit processes the sensor output and translates it into
electrical concentration, range, and alarm outputs, and a percent oxygen
meter readout. It contains a microcontroller that manages all signal
processing, input/output, and display functions for the analyzer.
2.2 Micro-Fuel Cell Sensor
2.2.1 Principles of Operation
The oxygen sensor used in the Model 3300TB series is a Micro-
Fuel Cell designed and manufactured by Analytical Instruments. It is a
sealed plastic disposable electrochemical transducer.
The active components of the Micro-Fuel Cell are a cathode, an
anode, and the 15% aqueous KOH electrolyte in which they are
immersed. The cell converts the energy from a chemical reaction into an
electrical current in an external electrical circuit. Its action is similar to
that of a battery.
There is, however, an important difference in the operation of a
battery as compared to the Micro-Fuel Cell: In the battery, all reactants
are stored within the cell, whereas in the Micro-Fuel Cell, one of the
reactants (oxygen) comes from outside the device as a constituent of the
sample gas being analyzed. The Micro-Fuel Cell is therefore a hybrid