Physikalisch-Technische Bundesanstalt

Since 1990, the quantum Hall effect is used in all National Metrology Institutes for the precise calibration of dc resistors. This raises the hope of using the quantum Hall effect also for precise calibration of ac resistors and capacitors. This application requires research, including the ac-dc transfer of calculable resistors.
	Printed circuit board with GaAs heterostructure, manufactured in the clean room facility of PTB

In the framework of a European research project, PTB, five other National Metrology Institutes and the Czech Technical University of Prague have developed a modular and automated system for the calibration of capacitors based on the ac quantum Hall effect. This project was finished successfully in October 2001.

The research on the ac quantum Hall effect is now continued in a collaboration with the National Metrology Institutes of Canada (NRC) and Switzerland (METAS). The aim is to overcome present technical and physical problems and to develop guidelines for reliable ac quantum Hall measurements.

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