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Teledyne Analytical Instruments
2-6
2 Operational Theory Model OT-2 System
2.2.5 Calibration Characteristics
Given that the total pressure of the sample gas on the surface
of the Micro-Fuel Cell input is constant, a convenient characteris-
tic of the cell is that the current produced in an external circuit is
directly proportional to the rate at which oxygen molecules reach
the cathode, and this rate is directly proportional to the concen-
tration of oxygen in the gaseous mixture. In other words it has a
linear characteristic curve, as shown in Figure 2-3. Measuring
circuits do not have to compensate for nonlinearities.
In addition, since the sensor output is approximately zero in the
absence of oxygen, the characteristic curve has close to an
absolute zero (within ± 1 ppm oxygen or better, depending on the
sensor type and model). In practical application, zeroing may still
be used to compensate for the combined zero offsets of the cell
and the electronics.
Figure 2-3. Characteristic Input/Output Curve for a Micro-Fuel Cell