Fig. 5 shows the dependence of the sensor response on the sensor bias voltage for a CeO2 sensor, with a CO concentration of 50,000ppm at a temperature of 390 ◦C. Fig. 5 depicts that there was a significant variation in response as the biasing voltages were increased. Similar results were observed for other temperatures in the range 300–500 ◦C. Therefore, from these findings, the bias voltage was fixed at 1.5V for subsequent experimental work.