YCAMIN Model 5500-series dissolved oxygen sensors use polarographic Clark Cell technology that includes a three-electrode system: gold cathode, silver anode, and silver reference electrodes. Fully-encapsulated construction protects the sensor's built-in electronics from moisture and humidity problems, extending the working life of the sensor. The Model D33 Dissolved Oxygen Analyzer is a panel mounnt, 1/4 DIN analyzer. This low priced, full-featured analyzer was specifically designed for the OEM and cost conscious end user.