Hamon 10x100 MΩ resistor based traceable source for calibration of picoammeters in the range 100 pA ÷ 100 nA

This paper describes a measurement method developed at National Institute of metrological Research (INRIM) to calibrate picoammeters in dc current from 100 pA to 100 nA. The current source is based on a traceable to the dc resistance national standard 10 x 100 M Omega Hamon resistor developed at INRIM and on a traceable to the dc voltage national standard high precision dc voltage calibrator. The expanded uncertainties of the method for the calibration of picoammeters span from 9.4 x 10(-4) for the gain of a picoammeter at 100 pA to 4.0 x 10(-4) for the gain at 100 nA. A detailed uncertainties budget at 10 nA level and the results of a comparison with a different technique are also reported