Stable and selective sulfur dioxide sensing elements operating at 800–900 centigrade

Sensing behavior of electrochemical transducers for the detection of sulfur dioxide (SO₂) is described. These elements operate at temperatures in the range 800-900 °C, and are constructed from oxide and precious metal electrodes on oxygenion conducting substrates. The responses to SO₂ at oxygen contents around 5% can be large, with 25 ppm SO₂ causing a 30-40% change in the sensing signal. This SO₂ response is shown to be little affected by oxides of nitrogen (NO_x), carbon monoxide, and propylene, present at the 100s of ppm level. Element stability is demonstrated over about 50 days of operation at temperature.