A yttria-stabilized zirconia (YSZ) tube with platinum electrodes was used for the measurement of potential with one electrode exposed to air and the other to H-2-H2O gas mixtures. Measurements were conducted over a temperature range from 30 degrees C to 475 degrees C using two different meters, one with an input impedance of 10 G Omega and the other with an input impedance >200 T Omega. With the high impedance meter (electrometer), a voltage of 0.93 V was measured at 30 degrees C, while it was much lower using the low impedance meter. Above similar to 177 degrees C readings from both meters converged. From the measurements, the actual cell voltage and the net cell resistance including all polarization resistances were estimated. Above 275 degrees C, the measured voltage was in agreement with the expected Nernst voltage. At lower temperatures, the voltage even with the electrometer was lower than the calculated Nernst voltage indicating that H2-H2O gas phase mixture did not reach equilibrium. Electrochemical impedance spectra (EIS) were obtained. From the EIS spectra, the ohmic resistance was obtained. Above 75 degrees C much of the cell resistance is attributed to electrode polarization. (C) 2016 The Electrochemical Society. All rights reserved.