Abstract: A probe immersible in liquid having oxygen dissolved therein and adapted to continuously and accurately measure the oxygen concentration. The probe includes a noble metal measuring electrode, a copper counter-electrode and a potassium hydroxide electrolyte which together define a galvanic cell whose output current depends on the amount of oxygen passing into the cell through a diffusion membrane permeable only to gases. The oxygen within the cell is electrochemically reduced at the surface of the measuring electrode to generate a current that is proportional to the oxygen concentration, the counter-electrode being oxidized.