Twenty commercially available oxygen meters using improved ThO2-Y2O3 electrolytes were tested at two sites. Repeated calibration by the vanadium equilibration method showed the slope of the curve to be constant and identical for all meters. One vanadium equilibration per month was sufficient to correct for drift of the intercept. Ten meters (at one site) were used continuously for 18 months without failure. Two oxygen meters are now in routine use in EBR-II primary sodium. The observed stability and life of the present meters are considered adequate for effective use in LMFBR sodium systems.