This article presents a new coulometric titration setup and describes the principles of operation, the main precautions to be taken into account to reduce the systematic errors, and evaluates the working range and the accuracy of the measurements. The major source of error, the oxygen leakage, is studied in detail and modeled based on leakage of oxygen through the YSZ solid electrolyte. Decreasing the difference in chemical potential of oxygen between inside and outside of the cell is studied as an applied measure to decrease the oxygen leakage. Flushing the pumping solid electrolyte by N-2 shows a reasonable improvement. Eventually, oxygen non-stoichiometry of SrFeO3-delta is measured at 1273 K in the oxygen partial pressure range of 0.6< -log(po(2)/atm) < 12. The resulting values are in good agreement with the literature. (C) 2012 Elsevier B.V. All rights reserved.