Teledyne 3000 Ultra Trace - PPB oxygen analyzer - Manual (Page 14)

2-2
2 Operational Theory Model Ultra Trace 3000
Teledyne Analytical Instruments
comes from outside the device as a constituent of the sample gas being
analyzed. The Micro-Fuel Cell is therefore a hybrid between a battery and a
true fuel cell. (All of the reactants are stored externally in a true fuel cell.)
2.2.2 Anatomy of a Micro-Fuel Cell
The Micro-Fuel Cell is a cylinder only 1¼ inches in diameter and 1¼
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 illus-
trates 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