The Model DO90 Trace DO2 sensor is designed for the continuous and accurate measurement of trace levels of dissolved oxygen, helping to maintain oxygen-free boiler feedwater and reducing corrosion. The unit is a lead-silver galvanic sensor with a durable PFA Teflon membrane. As a digital sensor, all of the signal conditioning, calibration and diagnostic functions are performed inside the sensor. Its signal is noise free and it features zero calibration and air calibration.