A system consisting of a high-temperature yttrium-stabilized zirconia (YSZ) based oxygen ion pump and potentiometric sensor enables precise measurement and control of oxygen partial pressure, p(O2), at elevated temperatures within 0.2 to 10(-20) bar. The principle of operation as well as the influence of temperature and gas buffers like H-2/H2O on the P-O2 is discussed. The ion pump is controlled by a microcontroller system and adjusts the oxygen partial pressure with an uncertainty of Delta log(p(O2)/bar) <0.02 and response times between 5 and 90 s over the entire P-O2 range. The oxygen ion pump is tested in combination with the electromagnetic levitation. Here, the surface tension of molten Ni at 1720 degrees C as a function of oxygen partial pressure is determined. A good agreement of this measurement with calculated value confirms the applicability of the system for high-temperature measurement and control of p(O2). The developed hardware is suitable for the electromagnetic levitation facility onboard the international space station (ISS). (C) 2012 Elsevier B.V. All rights reserved.