The Josephson-Effect-Based Primary AC Power Standard at the PTB: Progress Report
ABSTRACT This paper reports the incorporation of a Josephson waveform synthesizer (JWS) into the primary standard for AC electrical power at the Physikalisch-Technische Bundesanstalt (PTB). The increase to 10 V of the amplitude delivered by the JWS has allowed matching of the levels of the signals measured to determine the active, reactive, and apparent power-at the 120-V and 5-A level, which is also measured by the device under test. The inherent noise- and drift-free voltages delivered by the JWS allow calibration of the core sampling voltmeter of the PTB primary power standard with an uncertainty of 0.4 muV/V(k = 1) in 100 signal periods and as part of the measuring sequence.
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ABSTRACT: A chopper amplifier is presented that achieves an ultralow voltage noise of 0.73 nV/√Hz down to a few millihertz. Excess white and 1/ f current noise was observed, which increases with the chopping frequency. At the lowest chopping frequency of 570 Hz, a noise level of 40 fA/√Hz with a 1/ f corner at 3 mHz is obtained, corresponding to a noise temperature around 1 K at the optimum source impedance of 18 kΩ. Special care was taken to compensate the effect of switching spikes in the input chopper, resulting in a low charge injection into the signal source. The amplifier has a fixed gain of 1000. Postamplification and postfiltering with a wide range of settings, as well as optical output isolation based on a highly linear voltage-to-frequency converter, make the instrument well suited for demanding applications in metrology.IEEE Transactions on Instrumentation and Measurement 08/2011; · 1.36 Impact Factor
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ABSTRACT: This paper addresses the effect of transients on the operation of a 1-V programmable Josephson voltage standard for frequencies ranging between 125 Hz and 4 kHz. A detrimental effect of the transients occurring during the transition between different voltage steps is to make the ac Josephson voltage dependent on the bias current in the junctions. In other words, the current margins where the array behaves as a quantum standard are reduced to zero: the voltage steps have a slope. However, by using square waveforms, the effect of the transients can be reduced to a level where this slope is no longer measurable. This observation will probably lead to a simplification in the development of a new type of high-precision Josephson-based waveform synthesizer.IEEE Transactions on Instrumentation and Measurement 08/2010; · 1.36 Impact Factor
Conference Paper: Ultrapure sinewave generation by combining Josephson systems[Show abstract] [Hide abstract]
ABSTRACT: The combination of systems exploiting binary-divided and pulse-driven Josephson arrays allows the generation of sinewaves with amplitudes of up to 10 V and very low harmonic distortion (-122 dBc). We present results from the combination of a 1 V binary divided Josephson array employed as a multilevel digital to analogue converter and a pulse driven array that is programmed to cancel the harmonic content present in the stepwise approximated output of the binary array. The synthesized waveform can be locked to a timing reference for ultimate frequency stability. The quantum nature of the Josephson synthesizers guarantees the stability of the amplitude. The unprecedented amplitudes available with this spectral purity open new possibilities for testing of electronic modules and analogue to digital converters19th IMEKO TC-4 Symposium and 17th IWADC Workshop, Barcelona; 07/2013