The capacitance-charging method is a well-established and handy technique for the generation of dc current in the 100 pA range or lower. The method involves a capacitance standard and a sampling voltmeter, highly stable devices easy to calibrate, and it is robust and insensitive to the voltage burden of the instrument being calibrated. We propose here a range extender amplifier, which can be employed as a plug-in component in existing calibration setups, and allows the generation of currents in the 1 nA range. The extender has been employed in the INRIM setup and validated with two comparisons at 100 pA and 1 nA current level. The calibration accuracy achieved on a top-class instrument is 10 ppm at 1 nA.
Cite
@article{arxiv.1312.1838,
title = {Generation of reference dc currents at 1 nA level with the capacitance-charging method},
author = {Luca Callegaro and Pier Paolo Capra and Vincenzo D'Elia and Flavio Galliana},
journal= {arXiv preprint arXiv:1312.1838},
year = {2013}
}