低温电流比较仪电阻电桥的电流源开环测试

摘要

This paper introduces an open loop measurement method of current which applied to the cryogenic current comparator resistance bridge.The cryogenic current comparator using dc superconducting quantum interference device (dc-SQUID) as a feedback loop.The linear range of the superconducting quantum interference device is very smal ,little lager amount of input leading to the measurement process unstable,so it put forward higher requirements to the open loop cur-rent source.To test the highest ratio value of the current source,experiment uses standard resistance which is traceable to the quantum hal resistance,the calibration of the digital voltmeter and the proportion current source to form the resistance bridge to test the precision of the proportion.%介绍了一种应用于低温电流比较仪电阻电桥的电流源开环测试方法。低温电流比较仪的反馈环节使用dc－SQUID（dc－superconducting quantum interference device）。因为该器件的线性范围非常小，稍微大点的输入就会导致系统测量不稳定，因此对开环电流源的电流比率精度提出了较高的要求。电流源的输出在没有dc－SQUID反馈的条件下也接近平衡状态，也使得dc－SQUID有余量保证调节。电流源为可程控电流源，通过上位机改变DA的编码可以调节电流源的电流大小，使两路电流比率精度在一定范围内尽可能提高。为了测试该电流源的比率能够达到的最大精度，实验使用溯源到量子化霍尔电阻的标准电阻及校准过的数字电压表，与电流源构成电阻电桥进行测试。