Traceable precision generation and measurement of pA direct currents

Abstract

-We present the comparison of results from the generation and the measurement of direct currents in the pA range, performed with traceable state-of-the-art methods at highest accuracy. The currents were generated with the capacitor charging method, and measured with the first prototype of a novel picoammeter developed at PTB. The results confirm the agreement between both methods and the linearity of the new picoammeter at an uncertainty level of few µA/A. Also, they shed light on the ac-dc difference of capacitors, crucial for current generation with the capacitor charging method.

Improved calibration of instruments for small direct currents

“…The ULCA has proven to be a powerful tool for the highly accurate traceable measurement and generation of small electrical currents [1] - [4]. Earlier, its performance as electrometer was evaluated and validated in a comparison with the 'capacitor charging' method used for current generation in the sub-nA range [5]. In this paper, the first exemplary applications of the ULCA for calibrations of lowcurrent commercial state-of-the-art instrumentation, both for electrometers (picoammeters) as well as for low-current sources, are presented.…”