Teledyne 3000TA-EU - General purpose trace oxygen analyzer - Manual (Page 20)

Operational Theory 3000TA- EU
Teledyne Analytical Instruments
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2.2.2 Anatomy of a Micro-Fuel Cell
The Micro-Fuel Cell is a cylinder only 11/4 inches in diameter and
11/4 inches thick. It is made of an extremely inert plastic, which can be
placed confidently in practically any environment or sample stream. It is
effectively sealed, although one end is permeable to oxygen in the
sample gas. The other end of the cell is a contact plate consisting of two
concentric foil rings. The rings mate with spring-loaded contacts in the
sensor block assembly and provide the electrical connection to the rest
of the analyzer. Figure 2-1 illustrates the external features.
Figure 2-1: Micro-Fuel Cell
Refer to Figure 2-2, Cross Section of a Micro-Fuel Cell, which
illustrates the following internal description.
Figure 2-2. Cross Section of a Micro-Fuel Cell (not to scale)
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