A planar miniaturized SO2 sensor based upon a thick film of Ca2+ ion conductor-CaO center dot 0.6MgO center dot 6Al(2)O(3) (CMA) with a Na2SO4 auxiliary electrode and a Pt/O-2 reference electrode was fabricated and tested. The thick film was fabricated by screen-printing CMA ink on an alumina substrate and then fired at 1823 K. The solid electrolyte was interfaced with a sodium sulphate auxiliary phase containing Pt paste and the sensor showed a good SO2 response at 873-1073 K. The electromotive force (emf) values obtained were linearly dependent upon the logarithm values of SO2 concentration in a range of 10-500 ppm. Both the electrodes were exposed to the same test gas thus eliminating the need to separate the electrode chambers.