高场不对称波形离子迁移谱关键测控模块研究

Study on key measurement and control modules of high-field asymmetric waveform ion mobility spectrometer

研究了高场不对称波形离子迁移谱(high-field asymmetric waveform ion mobility spectrometer,FAIMS)两个关键测控模块:波形不对称高压产生模块和微弱电流检测模块的设计。通过采用反激升压原理,设计了一种电压幅度在线可调的波形不对称高压产生电路模块,其输出电压峰峰值达1 800 V,频率达1 MHz;微弱电流检测采用超高电阻反馈式I-V转换电路,并对失调电压进行补偿,同时结合PCB割板处理及包裹屏蔽等抗干扰措施,使得微弱电流模块的检测下限优于0.1 pA。最后,通过对比实验研究了不同波形不对称高压与分离效果关系,并以苯为样品对系统的检测下限进行了研究,结果表明采用上述测控模块的FAIMS检测下限达1×10-9。

This paper presents the development of two key modules for high-field asymmetric waveform ion mobility spectrometer（FAIMS） measurement and control system, i.e. , the high voltage asymmetric waveform generation module and the weak current detection module. The former is constructed by using flyback transformer principle, the voltage amplitude of the output high voltage can be adjusted on line and the peak-to-peak amplitude of the asymmetric waveform is up to 1 800 V and the maximum frequency reaches as high as 1 MHz. The latter is designed by adop- ting an uhra-high feedback resistor I-V conversion circuit, and the offset voltage is compensated. When constructing the weak current detection module, the design measures against the influence of PCB EMC, leakage current, as well as shielding and grounding techniques are adopted. Experimental results indicate that the detecting limit of this mod- ule can be as low as 0.1 pA. Experiments were performed to verify the separation efficiency for different voltages applied to the separation electrode. Benzene is used as a sample to study the detecting low limit, and the detecting low limit of the FAIMS system is about 1 × 10-9 .