GfG ZD121 Oxygen Fixed Transmitter is a robust transmitter when there are harsh environmental conditions such as varying temperatures, high or low pressure or dry or humid air. The sensor operates with a zirconium dioxide oxygen pump cell. The ZD 21 is an intelligent fixed transmitter for the detection of oxygen. The comprehensive electronics allow for easy operation and maintenance and also increase operational safety and accuracy. In less than two seconds the ZD 21 responds to an oxygen deficiency. This extremely quick response time allows the time to take measures to prevent considerable damage.