Abstract: The cell EMFs of oxygen in an evacuated (air) system (10⁵～10³Pa) versus atmospheric oxygen were measured from 600℃　to 800℃ by an
oxygen concentration cell with a solid electrolyte of yttria stabilized zirconia. The experimental results showed that there is a linear relationship between the cell
EMF and the logarithm of residual atmospheric pressure p in an evacuated (air) system. The produced EMF is given by the eqution E=(RT/4F)ln(p_air/p),
in which it’s slope is close to theoretic value and error less than 5%. The sensibility of measured EMF increases with the pressure decrease and may be suitable for low
vacuum measurement.

Key words: low vacuum measurement, yttria stabilized zirconia, zirconia oxygen sensor, zirconia oxygen concentration cell