Teledyne 3220 - Multi-channel oxygen monitor system - Manual (Page 25)

Oxygen Monitor System 2 Operational Theory
Teledyne Analytical Instruments 11
Figure 2-5 illustrates a cross section of a Micro-fuel cell.
At the top end of the cell is a diffusion membrane of Teflon, whose
thickness is very accurately controlled. Beneath the diffusion membrane
lies the oxygen sensing element the cathode-with a surface area almost
4 cm
2 . The cathode has many perforations to ensure sufficient wetting of
the upper surface with electrolyte, and it is plated with an inert metal.
The anode structure is below the cathode. It is made of lead and has
a proprietary design which is meant to maximize the amount of metal
available for chemical reaction.
Figure 2-5: Cross Section of a Micro-fuel Cell
At the rear of the cell, just below the anode structure, is a flexible
membrane designed to accommodate the internal volume changes that
occur throughout the life of the cell. This flexibility assures that the
sensing membrane remains in its proper position, keeping the electrical
output constant. The entire space between the diffusion membrane,
above the cathode, and the flexible rear membrane, beneath the anode, is
filled with electrolyte. Cathode and anode are submerged in this
common pool. They each have a conductor connecting them to one of
the external contact rings on the contact plate, which is on the bottom of
the cell.