A kind of carbon monoxide sensor is designed.The sensing material of sensor is SnO2 semiconductor

and three electrodes direct-heating is used as heating style

square-wave pulse is used as power supply.The effects of working voltage and sampling time on anti-interference and sensitivity are investigated.The results show that sensitivity is about 10 and anti-interference coefficient is above 100 under the condition of working voltage of 0.3V and sampling time of 20s.