Max-Planck-Institut, Stuttgart

Metrology guarantees the worldwide uniformity of all measurements and most countries have accepted the SI system (International System of Units) as the basis for accurate measurements. Four base units (meter, second, kilogram and Ampere) fix all units in mechanics and electricity but this system may change in 2011. The quantum Hall effect (QHE), which leads to a resistance stable and reproducible with an uncertainty smaller than 10 -10, plays an important role in the discussion of new SI base units. The talk summarizes the most important applications of the quantum Hall effect in metrology and will answer questions like: What is the accuracy of the quantized Hall resistance, why is the QHE important for high precision measurements of fundamental constants and what are the connections of this quantum resistor to the unit of mass, the kilogram?