Servomex’s Zirconia sensor consists of a cell made of ceramic zirconium oxide, stabilized with an oxide of yttrium or calcium, that forms a lattice structure. The cell is coated with a conductive coating that serve as electrodes on both sides of the lattice. At temperatures above 700°C, the openings in the lattice permit the passage of O2 ions; When a sample gas is introduced on one side of the lattice, O2 ions pass through at a rate determined by temperature and the difference in the O2 partial pressures of the sample gas and the reference gas (usually air) on the other side of the lattice. The passage of O2 ions through the lattice produces a voltage across the electrodes, the magnitude of which is a logarithmic function of the ratio of the O2 partial pressures of the sample and reference gas. Since the partial pressure of the reference gas is predetermined, the voltage produced by the cell indicates the oxygen content of the sample gas.
A Zirconia-based oxygen analyzer exhibits excellent response characteristics to changes in O2 content at ppm levels, and the same sensor can be used to measure 100% O2.. Zirconia’s major advantage is that it can be used in in-situ instruments such as the SERVOTOUGH FluegasExact 2700, where the measuring probe can be placed directly into a flue for high-temperature combustion gas analysis, eliminating the need for extractive sampling equipment.