A new method was proposed by us to measure the electronic conduction parameter, P-e’. The measuring condition of the new method is the same as the working environment of expendable oxygen sensor, so, the P-e’ data measured by using this method are suitable to be used for the calculation of oxygen concentrations of steel melts. A new tube with a thin Y2O3-fully stabilized zirconia layer (3-5 micrometers) coated on the MgO-partially stabilized zirconia electrolyte tube has been developed. The double layer tube shows much lower electronic conductivity. The auxiliary electrode method developed for measuring other element concentrations is also summarized in this paper.