For optimum quality and process protection, the avoidance of oxygen, also as traces, is necessary in many technological applications. Due to the increasing adoption of quality management systems (e.g. ISO 9000), a constant monitoring and documentation of quality parameters becomes more important. The oxygen measuring module ZR5 is based on the approved zirconia technology. It serves the continuous measurement of oxygen concentration in industry and laboratory gases and the monitoring of protective gases. Deviations of the oxygen concentration from set points can be signalized, the ZR5-module can monitor the procedure of special production processes under inert gas.