Smell selective gas sensor with modulation heating

We propose a new method to distinguish smells using an SnO/sub 2/ gas sensor. We have measured the sensor response on heating up with several shaped voltages to improve its selectivity. The delay time of the response on heating by a triangular pulse voltage was different from that of alcoholic smells, and depended on the rise velocity of the triangular pulse. The triangular pulse with a rise velocity of 43 mV/sec gave us the largest delay time difference for various alcoholic smells. In the case of methanol and propanol, the difference reached around 12 sec. These results show a smell selective sensor can be realized using a SnO/sub 2/ gas sensor with modulation heating, such as supplying a triangular pulse to the heater.