Title :
Improving the Traceable Measurement and Generation of Small Direct Currents
Author :
Drung, Dietmar ; Gotz, Martin ; Pesel, Eckart ; Scherer, Hansjorg
Author_Institution :
Phys.-Tech. Bundesanstalt, Berlin, Germany
Abstract :
We present the latest improvements in the traceable measurement and generation of small electric currents. A central tool in our traceability chain for small direct currents is a new binary cryogenic current comparator (CCC) with a total of 18276 turns. This 14-bit CCC is well suited for the calibration of highvalue resistors and current amplifiers, but also for the direct amplification of small currents. A noise level of 5 fA/√Hz at 0.05 Hz is routinely achieved. The systematic uncertainty due to noise rectification was exemplarily investigated in a ratio-error test configuration, showing that a total uncertainty of about one part in 106 can be achieved at 100 pA. For further improvement, a new instrument was developed, the ultrastable low-noise current amplifier (ULCA). Its transfer coefficient is highly stable versus time, temperature, and current amplitude within a full dynamic range of ±5 nA. The ULCA is calibrated with the 14-bit CCC at high current amplitude, and allows the measurement or generation of 100-pA direct current with an uncertainty of one part in 107. The novel setup was successfully used to investigate the uncertainty of the established capacitor charging method. A quantum metrology triangle experiment based on the presented instruments is proposed.
Keywords :
DC amplifiers; DC generators; calibration; electric noise measurement; measurement uncertainty; binary cryogenic current comparator; calibration; noise rectification; quantum metrology triangle experiment; ratio-error test configuration; small direct currents; small electric current generation; systematic uncertainty; traceable measurement; transfer coefficient; ultrastable low-noise current amplifier; Current measurement; Measurement uncertainty; Noise; Noise measurement; SQUIDs; Uncertainty; Windings; Ammeters; amplifiers; calibration; instrumentation and measurement; measurement units; noise measurement; superconducting devices; uncertainty; uncertainty.;
Journal_Title :
Instrumentation and Measurement, IEEE Transactions on
DOI :
10.1109/TIM.2015.2440564