Teledyne 3350 - Microprocessor based control room monitor for personnel safety - Manual (Page 12)

2-2
2 Operational Theory Model 3350
Teledyne Analytical Instruments
2.2.2 Anatomy of a Micro-Fuel Cell
The Micro-Fuel Cell is made of extremely inert plastic (which can be
placed confidently in practically any environment or sample stream). It is effec-
tively sealed, though one end is permeable to oxygen in the sample gas. At the
permeable end a screen retains a diffusion membrane through which the oxygen
passes into the cell. At the other end of the cell is a connector and temperature
compensation network (restrictors and thermistor) on a printed circuit board.
Refer to Figure 2-1, Basic Elements of a Micro-Fuel Cell, which illus-
trates the following internal description.
Figure 2-1. Basic Elements of a Micro-Fuel Cell (not to scale)
At the sensing end of the cell is a diffusion membrane, whose thickness is
very accurately controlled. Near the diffusion membrane lies the oxygen sensing
element—the cathode.
The anode structure is larger than the cathode. It is made of lead and is
designed to maximize the amount of metal available for chemical reaction.
The space between the active elements is filled by a structure saturated with
electrolyte. Cathode and anode are wet by this common pool. They each have a
conductor connecting them, through some electrical circuitry, to one of the
external contacts in the connector receptacle, which is on the top of the cell.
Electrical Connector
Circuit Board
with temperature compensation network.
Cathode
Anode
Clamp
Teflon Membrane
Screen