871DO DISSOLVED OXYGEN SENSORS FOXBORO

The Foxboro® brand Model 871DO-C Sensor is available from Invensys PRocess Systems (IPS). This sensor, when used in conjunction with 871DO-C Sensor Accessories and the 873DO Electrochemical Analyzer, provides a reliable and accurate measurement of dissolved oxygen in aqueous streams, ponds, and industrial processes. As symbolized by the “CE” marking, these sensors conform to the applicable European Union Directives.

GENERAL DESCRIPTION

The 871DO-C Sensor measures dissolved oxygen by using a 3-electrode cell and the Clark Polarographic Method. A fourth electrode is used for sensor diagnostics. The cell electrodes, contained within an electrolyte, are isolated from the process medium by an extremely durable, oxygen-permeable, composite membrane made of tetrafluoroethylene (tfe) and dimethylsilicone rubber. This composite membrane is reinforced with a stainless steel mesh. A fixed potential is maintained between the gold working

cathode and the silver/silver chloride (Ag/AgCl) reference electrode. Dissolved oxygen in the process solution permeates the composite membrane and is electrochemically reduced at the cathode. This electrochemical reaction produces a small current that is proportional to the concentration of dissolved oxygen in the process solution. A gold test electrode within the sensor enables diagnostic performance testing.