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Percent Oxygen Analyzer
Operational Theory
2.1 Introduction
The analyzer is composed of two subsystems:
1. Analysis Unit with Oxygen 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 oxygen sensor. The oxygen sensor 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 micro-controller that manages all signal
processing, input/output, and display functions for the analyzer.
2.2 Oxygen Sensor
2.2.1 Principles of Operation
The oxygen sensor used in the Model 3290 is a micro-fuel cell
designed and manufactured by TAI. It is a sealed, disposable
electrochemical transducer.
The active components of the oxygen sensor, also referred to as the
sensor cell or just cell, are a cathode, an anode, and the 15% aqueous
KOH electrolyte for the typical oxygen sensor in which they are
immersed. The cell converts the energy from a chemical reaction into an
electrical potential that can produce a 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 oxygen sensor or 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 oxygen sensor is
Teledyne Analytical Instruments
Operational Theory
7
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