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Trace Oxygen Analyzer Operational Theory
Teledyne Analytical Instruments 7
Operational Theory
2.1 Introduction
The analyzer is composed of three subsystems:
1. Micro-Fuel Cell Sensor
2. Sample System
3. Electronic Signal Processing, Display and Control
The sample system is designed to accept the sample gas and
transport it through the analyzer without contaminating or altering the
sample prior to analysis. The Micro-Fuel Cell is an electrochemical
galvanic device that translates the amount of oxygen present in the
sample into an electrical current. The electronic signal processing,
display and control subsystem simplifies operation of the analyzer and
accurately processes the sampled data. The microprocessor controls 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 3000T 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
between a battery and a true fuel cell. (All of the reactants are stored
externally in a true fuel cell.)