Abstract: An improved sensor for dissolved oxygen measurement comprising a body having an electrolyte reservoir and electrolyte contained therein and an opening for communication between the exterior of the body and the reservoir and an anode and cathode concentrically disposed in the body adjacent the opening. A thin polymeric membrane permeable to oxygen and impermeable to the electrolyte seals the opening. The working surfaces of the anode and cathode, that is the surfaces adjacent the membrane, are spaced apart from the membrane to define an electrolyte space between the working surfaces and the membrane. A noble metal screen is disposed on the working surface of the anode. Preferably the screen completely covers the anode working surface and a portion of the screen which would normally overlie the working surface of the cathode is cut away so that the cathode working surface is unobstructed.