【摘要】 本文阐述了一种新型恒温恒流大气采样方法。恒流部分采用流量传感器和ＰＩ控制模式，组成无差调节系统，实现了２００ｍｌ／ｍｉｎ小流量气体的精确控制；恒温部分采用半导体制冷元件，结合反馈与前馈的复合控制模式，实现制冷温度的精确控制。脉冲宽度调制芯片与ＰＴＣ材料组合的方案在本方法中得到了成功的应用。更多还原

【Abstract】 This thesis is on a new sampling method for steady temperature and constant flow air. In the con- stant flow part, flow sensors and PI mode compose a non-error adjustment system to achieve the exact control of a little air flow (under 200 ml/min).In the thermal controling system, semiconductor refogerant technology isjoin- ed with feedback and feedforward to control the temperature exactly.Also the project of joining pulse width chip with PTC material is successful in this method.更多还原