AquaMetrix has been making dissolved oxygen sensors for the five decades it has been in business. The 2200D analyzer and P91 sensor are Clark (membrane) based electrochemical systems and are proven in hundreds of wastewater treatment plants around the world. It is still the sensor technology of choice in Asia and much of Europe. The newer optically based probe is a new addition to the AquaMetrix product line. it’s made for us by the world leader in biopharmaceutical sensors and provides both 4-20 mA analog and Modbus digital outputs.