Real-time oxygen measurement gives critical feedback to improve process efficiency and safety in a wide range of industries, including:
One proven method for measuring oxygen is the zirconia oxygen sensor. This technology is employed in AMETEK's Thermox® and clean gas analyzers, which provide reliable and accurate real-time measurements.
The zirconia oxygen sensor consists of two basic components: the electrolyte and the electrode. The electrolyte is typically made using a partially or fully thermally stabilized zirconium oxide (also known as “zirconia”) ceramic doped with yttrium oxide (also known as yttria), magnesium oxide (MgO), or calcium oxide (CaO). Depending on the industry and application, the shape and configuration of the sensor may vary. The electrode is made by applying a thin, porous platinum (Pt) coating on both sides of the zirconia.
In the Thermox and clean gas sensors, the oxygen sensor is a closed-end tube of zirconia. The inside of the tube maintains the known reference content of oxygen (typically ambient air with 20.9% oxygen) while the outside of the tube is exposed to the process sample gas or the unknown oxygen content.
Figure 1. Diagram of a zirconia closed-end tube sensor.
When heated above 600°C, zirconia becomes ionically conductive and allows oxygen ions to pass through the open interstitial sites within the ceramic itself. These oxygen ions are energetically driven for equilibrium between the two sides of the zirconia. This movement of ions creates a potentiometric voltage or cell potential (ECell) that is measured and allows the calculation of the unknown oxygen content using the Nernst equation.
Figure 2. Diagram showing the exchange of oxygen ions through the zirconia creating a voltage or cell potential.
Developed in 1887 by a German chemist Walther Hermann Nernst, the Nernst equation calculates the cell potential at a known temperature and pressure.
By holding the temperature constant, the voltage generated correlates the ratio of partial pressures between the process sample and reference gas. By solving the Nernst equation for the
oxygen measurement is calculated for the process.
Oxygen analysis via a zirconia oxide sensor is a reliable and accurate way to monitor and maintain a facility’s safety and optimize its processes.
Learn more about AMETEK’s zirconia oxide analyzers.