Teledyne Operational Theory Model OT-2 System, Micro-Fuel Cell Sensor Principles of Operation

2 Operational Theory Model OT-2 System

2.2Micro-Fuel Cell Sensor

2.2.1Principles of Operation

The oxygen sensor used in the Model OT-2 System is a Micro- fuel Cell designed and manufactured by Analytical Instruments. It is a sealed plastic disposable electrochemical transducer.

The key components of the Micro-Fuel Cell are a diffusion

barrier in the form of a thin membrane, a cathode, an anode, and an electrolyte in which they are immersed.

Oxygen from the sample gas diffuses through the thin mem- brane and is reduced at the cathode. As a result, an electrical current is produced that is proportional to the concentration of oxygen in the sample gas.

The choice of electrolyte, and hence the sensor type, de- pends on the exact constituents of the sample gas. For sample gases that contain a high concentration of CO2, for example, an acid electrolyte will be the more optimal choice.

2.2.2 Anatomy of a Micro-Fuel Cell

The Micro-fuel Cell is approximately 1¼ inches in diameter. The cell body is made of an inert plastic that is compatible with a wide variety of sample streams. Oxygen from the sample gas diffuses through a thin membrane located at one end of the sensor. The other end of the cell is a contact plate consisting of two concentric foil rings. The rings mate with spring-loaded con- tacts 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

2-2 Teledyne Analytical Instruments