用于FAIMS系统的微电流检测电路屏蔽

摘要

In order to solve the problems of the capacitance integral circuit which cannot meet the requirement of fast detection for FAIMS, a new design of circuit for micro current detection is introduces. Proper components and circuit design are adopted to amplify pA current up to mV order of magnitude with various noise sources of pre-circuit taken into consideration. In the experiment, the current signal is collected and processed by NI acquisition board under the control of Lab VIEW, and the result shows that the measurement accuracy of the circuit is lower than 0. 1 pA and the sampling frequency can reach 15 Hz. In the real FAIMS test, the system background noise acquired by the circuit is 0. 2 pA and the FAIMS spectra of ethanol is obtained under the condition of carrier gas flow of 0. 8 L/min and the compensation voltage from -4 V to 6 V at 0. 1 V sweeping step. The circuit can meet the requirements of FAIMS well.%为解决电容积分式电流检测法不能满足FAIMS快速测量要求的问题,设计了一种用于FAIMS系统的微电流检测电路.采用合理的元器件和电路设计,运用两级放大将FAIMS系统中的pA级电流放大并转换到mV量级.为了消除FAIMS系统中高频噪声的干扰,对电路进行屏蔽设计,从而有效滤除了系统的干扰噪声,放大后的信号通过NI采集卡,并利用LabVIEW对测得的电流信号进行采集和数据处理.实验结果表明,该电路的测量精度优于0.1 pA,采样频率高于15 Hz.进行了FAIMS系统实验,测得系统输出的背景噪声为0.2 pA.以乙醇为实验样品,在载气(N2)流量为0.8 L/min的情况下,得到了乙醇的FAIMS谱图,证明了该微电流检测电路屏蔽能有效滤除FAIMS系统的噪声干扰.