Aiming at the semi-conductor gas sensor's shortcoming of poor selectivity,a method of temperature modu⁃lation detection is applied to achieve better detection performance for combustible gas. A parameter-adjustable sys⁃tem for gas sensor temperature modulation is designed. This system outputs sine wave and square wave which have adjustable frequency characters from 0 to 1 000 Hz,adjustable amplitude characters from 0 to 5 V,and an adjust⁃able duty-cycle character for square wave,also the overall design scheme and hardware design circuit are given in this paper. By using the self-made side-heated type SnO2 sensor and applying the method of square wave tempera⁃ture modulation,optimized temperature modulation parameters are obtained after detection and analysis on the two kinds of combustible gases,CO and CH4. This paper gives an idea that the temperature modulation amplitude ratio, calculated by the value the sensor responded in the air and in the measured gas,could be used as the sensitivity co⁃efficient. The testing results demonstrate that CO and CH4 gas give good approximate linearity by applying the square wave temperature modulation method for 10s period,and the linearity difference is good. The result indicates that the two kind of gases have different selectivity.%针对半导体气体传感器存在选择性差的问题，通过温度调制检测方法实现可燃性气体良好检测性能，提高传感器在复杂环境下的选择性。设计了一种参数可调的气体传感器温度调制系统，实现了正弦波和矩形波输出模式，输出频率0~1000 Hz，幅值0~5 V可调，矩形波占空比可调，并给出了系统总体设计方案和硬件设计电路。通过自制旁热式SnO2传感器对CO和CH4两种可燃性气体进行了矩形波温度调制检测分析，得到了优化的温度调制参数。提出以传感器在空气和被测气体响应中温度调制幅值比作为灵敏度系数。测试结果表明，CO和CH4气体在周期10 s的方波温度调制下呈良好的近似线性规律变化，且具有较好的线性度差异，表明两种气体具有选择性差异。
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