The Milwaukee MA845 is a polarographic replacement probe for the MW190 MAX Dissolved Oxygen Bench Meter. The refillable polarographic probe has an oxygen-permeable polytetrafluroethylene (PTFE) membrane sensor for measuring dissolved oxygen (DO) levels in aqueous solutions. The MA845 probe uses a platinum cathode and a silver chloride anode which the MW190 MAX meter polarizes so that oxygen passing through the membrane can be measured to produce stable, accurate readings.