Abstract: Low-current test instruments (such as the electrometer, Pico ammeters, source/measure units, semiconductor precision analyzers, etc.) play an extremely important role in the electronic and aerospace field and model engineering. The current measurement resolution level of fA grade touched its physical limit. It is a new metrology challenge that the precision low current measurement instruments of high sensitivity and strong resolution are calibrated. Fluke Instrument's 5440B and self-developed NIM-TΩ was used to constitute test platform in this article to calibrate Keithley Instrument's 6517B (current range: 20pA~2μA). Visual C + + 6.0 was used to develop calibrating software through analysis of measurement results. The metrology difficult problem of low current measurement unit calibration was solved.

Key words: Low Current measurement unit, Parameters calibration, Calibration algorithm