Teledyne BDS-3000 - Oxygen analyzer - Manual (Page 23)

Oxygen Analyzer Operational Theory
Teledyne Analytical Instruments 9
impurities in the electrolyte. It eliminates the internal background
current which previously limited the detection process.
The second potentiostat is located adjacent to the sensing electrode.
It uses a novel material, Reticulated Vitreous Carbon (RVC) and precise
control of the potential to remove the dissolved oxygen and impurities in
the electrolyte efficiently. As the result, the BDS sensor achieves an
outstanding feature of absolute zero output in the absence of oxygen.
Figure 2.1: Cross Section of the BDS Oxygen Sensor
Figure 2.1 shows the schematic of a BDS oxygen sensor. The
sample gas enters the sensor through the gas inlet port and exits at the
gas outlet. A portion of oxygen in the sample gas diffuses through the
diffusion barrier to be reduced at the sensing electrode to form OH
-
in
the electrolyte. OH
-
can move freely through the porous 2nd working
electrode. At the Counter Electrode, OH - is oxidized back to oxygen.
While the 2nd working electrode allows OH
-
to move through, it
prevents the dissolved oxygen from the top portion of the sensor to reach