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Calibrating inductive voltage dividers

Pulse-driven Josephson voltage standards used for voltage ratio measurements

PTBnews 3.2018
02.10.2018
Especially interesting for

AC voltage metrology

power quality analysis in power grids

PTB is developing a measuring system based on pulse-driven Josephson voltage standards. This system is designed to allow alternating voltages to be measured with great accuracy at frequencies of up to 100 kHz and voltages of more than 100 V. Since the output voltages of Josephson voltage standards are limited to a few volts, it is necessary to use voltage dividers. An inductive voltage divider has now been calibrated for the first time with pulse-driven Josephson voltage standards, and the results have been compared to those obtained using a conventional calibration procedure.

Schematics of the measurement setup for the calibration of the inductive voltage divider (in the figure: ”divider”) with the two JAWS voltage standard systems. The lock-in voltage amplifier together with the transformer (centre of the picture) amplifies the signal and, thus, increases the sensitivity of the measurement method.

Inductive voltage dividers are highprecision AC transformers used to realize voltage ratios in electric metrology as the core elements of, for example, voltage or impedance bridges. Until recently, they were calibrated using a time-consuming traditional procedure based on the socalled “bootstrapping” method in which each of the individual segments of the divider is compared with the others one by one.

The accuracy of this calibration procedure has now been checked with quantum precision by means of an inductive, decadic voltage divider using two independent, pulse-driven Josephson voltage standards (Josephson Arbitrary Waveform Synthesizers – JAWS). For this purpose, effective voltages of 100 mV were generated by means of one of the JAWS systems and applied to the divider as an input signal, whereas the second JAWS system was used to compensate for the output signal of the divider. The results obtained within the scope of this compensation measurement for the correction of the reactive component showed excellent agreement with the bootstrapping method: the relative difference amounted to less than 10–8.

Furthermore, it was possible to demonstrate that, when applied to the divider, additional harmonic signal components of the input signal had a negligible influence on the calibration of the divider. The conventional bootstrapping procedure has thus been verified with quantum precision and can now also be used for calibrations at higher voltages. In addition, it is planned to test the new quantumbased method for the calibration of new broadband resistive voltage dividers.

Using JAWS systems in combination with voltage dividers paves the way for novel potential applications such as the power quality analysis of sinusoidal voltage signals in power grids.

Contact

Jonas Herick
Department 2.6
Electrical Quantum Metrology
Phone: +49 531 592-2135
Opens window for sending emailjonas.herick(at)ptb.de

Scientific publication

J. Herick, S. Bauer, R. Behr, M. F. Beug, O. F. O. Kieler, L. Palafox: Calibration of an inductive voltage divider using pulse-driven Josephson arrays. Conference Digest CPEM – “Conference on Precision Electromagnetic Measurements”( 2018)