中文摘要：

研制了基于dc—squid（dc—superconducting quantum interference devices）的低温电流比较仪，通过实验及分析，其电流分辨率为7．1fA／Hz^1/2，比例误差小于10^-11量级，将该低温电流比较仪应用于微弱电流精密测量，通过溯源到量子化霍尔电阻的1kQ标准电阻以及校准过的数字电压表对低温电流比较仪放大后的副边电流进行测量，进而构成微弱电流精密测量系统，实现微弱电流的精密测量，对于（1～10）μA的电流测量，理论标准不确定度小于1×10^-8，最高可达到1×10^-9；利用该测量系统对目前商用最好的微电流源表进行初步测量，其灵敏度远远高于源的稳定性，完全满足目前nA级以上微弱电流精密测量要求。

英文摘要：

A cryogenic current comparator based on dc-direct superconducting quantum interence devices （dc- SQUID） was designed. The experiment and analysis show that the ratio error of the cryogenic current comparator is below 10 and the current resolution is 7.1 fA/Hzj/2. The cryogenic current comparator was applied to low current precision measurement. A 1 kf~ standard resistor traced to the quantum hall resistance and a calibrated digital voltme- ter were used to measure the amplified secondary side current of the CCC,which forms a low current precision meas- urement system and the accurate measurement of low current is realized. The theoretical standard uncertainty of the system is below 1 × 10^- 8 and reaches 1 × 10^-9 at most in the current measurement of （1 -10）μA. The measurement system was used to measure the best commercial current source meter in a simple experiment;the result shows that the sensitivity of the measurement system is much better than the stability of the current source, which can completely meet the requirement of low current precision measurement above nA level.