节点文献
电阻式皮安级微电流源技术研究
Research on Resistive Picoampere Micro Current Source Technology
【作者】 梁伟;
【导师】 齐明;
【作者基本信息】 哈尔滨工业大学 , 电气工程, 2021, 硕士
【摘要】 微电流的产生对航天、通信、医学、生物等许多领域的发展有着重要意义,微电流的测试也在各种科学研究和工业领域中有着广泛的应用,无论是微电流的产生还是测试都离不开微电流源。国内对于微电流源方面的研究起步较晚,主流的微电流源设备的分辨率和稳定性等关键指标均与发达国家存在一定差距,针对这一问题,本文开展了对微电流源技术的研究,主要进行了以下几个方面的研究工作:首先,对可以产生直流微电流的几种基本电路进行了研究,在此基础上对比分析国外皮安级微电流源的设计原理,选择了电阻式的实现方案,进而确定了整个直流微电流源系统的总体设计方案。其次,对直流微电流源系统设计过程中的关键技术进行了研究。主要是漏电和噪声等问题。为了解决电路板绝缘不足的问题,在重要的需要防漏电的地方采用了聚四氟乙烯绝缘端子;在高值电阻(10~9Ω以上)表面涂低吸湿性绝缘漆,防止空气湿度影响其阻值;采用双层屏蔽的高绝缘继电器,来减小继电器上产生的漏电流。对静电计运放这一重要器件的选择和使用进行了研究,并对系统的噪声进行了分析,提出了噪声的抑制措施。再次,对系统各个部分的硬件电路进行了设计。设计了基于16位脉冲宽度数模转换器的电压源电路,可实现0.2V-20V三个量程电压的精确调节,分辨率在1m V以上。对电压电流转换电路进行了设计和仿真分析,对各个量程的电阻和继电器进行了选型。为了保证静电计运放的超低偏置电流特性,设计了自举式的电压检测电路,并采用了保护环结构,通过仿真分析证明了该结构的有效性。最后,搭建了直流微电流源系统的试验平台,编写了基于LabWindows/CVI开发平台的上位机程序和基于ARM平台的下位机程序,对系统进行实验研究。首先对关键子电路部分的输出进行了测试,然后分别测试了直流微电流源系统无源式输出和有源式输出两种情况的短期稳定性,实验结果表明,有源式输出的不确定度要高于无源式输出,且两种输出结果均可以满足本次设计的最高不确定度为0.5%的设计指标。
【Abstract】 The generation of micro-current is of great significance to the development of many fields such as aerospace,communications,medicine,biology,etc.The test of micro-current is also widely used in various scientific research and industrial fields,whether it is the generation of micro-current or the test.Do not open the micro current source.Domestic research on micro-current sources started relatively late,and the resolution and stability of mainstream micro-current source equipment are far behind those of developed countries.In response to this problem,this article carried out research on micro-current source technology,Mainly carried out the following research work:First of all,several basic circuits that can generate DC micro-current are studied,and on this basis,the design principles of foreign pico-ampere-level micro-current sources are compared and analyzed,and the resistive implementation scheme is selected,and then the entire DC micro-current source is determined.The overall design of the system.Secondly,the key technology in the design process of DC micro current source system is researched.Mainly problems such as leakage and noise.In order to solve the problem of insufficient insulation of the circuit board,PTFE insulated terminals are used in important places that need to prevent leakage;low-hygroscopic insulating paint is coated on the surface of high-value resistance(above 10~9Ω)to prevent air humidity from affecting its resistance;A double-layer shielded high-insulation relay is used to reduce the leakage current generated on the relay.The selection and use of electrometer op amp,an important device,are studied,and the noise of the system is analyzed,and noise suppression measures are proposed.Third,the hardware circuits of each part of the system are designed.A voltage source circuit based on a 16-bit pulse width digital-to-analog converter is designed,which can achieve precise adjustment of voltages in three ranges of 0.2V-20V,with a resolution of more than 1m V.The voltage-current conversion circuit is designed and simulated,and the resistors and relays of various ranges are selected.In order to ensure the ultra-low bias current characteristics of the electrometer op amp,a bootstrap voltage detection circuit is designed and a guard ring structure is adopted.The effectiveness of the structure is proved by simulation analysis.Finally,a test platform for the DC micro-current source system was built,and the upper computer program based on the LabWindows/CVI development platform and the lower computer program based on the ARM platform were written to conduct experimental research on the system.First,the output of the key sub-circuit part was tested,and then the short-term stability of the passive output and active output of the DC micro-current source system were tested.The experimental results showed that the uncertainty of the active output It is higher than the passive output,and both output results can meet the design index with the highest uncertainty of 0.5%in this design.
【Key words】 DC micro current source; resistive type; leakage current; noise; error analysis;