New scales for the new kilogram

July 14, 2017
By the end of this year, scientists will have access to an initial prototype of the Planck scale. Credit: TU Ilmenau

The Planck scale works according to the principle of electromagnetic force compensation: A weight force on one side of the scale is balanced by an electromagnetic force on the other side. This means that weights (so-called mass standards) will no longer be needed. This could be the beginning of the development of a completely new generation of scales that are suitable for industry.

Together with the Technische Universität Ilmenau, the Physikalisch-Technische Bundesanstalt (PTB) is developing a so-called Planck . This scale works according to the principle of electromagnetic compensation: A weight force on one side of the scale is balanced by an electromagnetic force on the other side. This means that weights (so-called mass standards) will no longer be needed; to date, weights have "told" scales how large the mass on the scale actually is (for example, 1 kg). By the end of this year, scientists will have access to an initial prototype of the Planck scale. In this way, a review can be carried out of the steps that are still necessary to develop the scale to the point that it is suitable for industrial use. This could be the beginning of the development of a completely new generation of scales that are suitable for industry.

The development of the Planck scale was lent momentum by the approaching redefinition of the kilogram: In the near future, the international prototype of the kilogram, a small metal cylinder in a safe near Paris, will become obsolete. In its place, a kilogram definition will be used that is based on an indestructible and unchanging natural constant: Planck's constant h. The name "Planck scale" alludes to this very constant. Once the value of h is established internationally, masses will be determined solely by measuring electrical quantities.

An additional advantage of the Planck scale is its continuous measuring range. Although the initial prototype will only achieve a measuring range from 1 mg to 100 g, its successor, which has already been planned, will have a range from 1 mg to 1000 g. Comparable scales could be used for industrial weighing operations as so-called primary standards, since no calibration using standard weights will take place. In the long term, however, the Planck scale could also be used to achieve higher accuracy (even for small masses) than has been possible to date using standard weights in industrial applications. In this way, the expertise gained at PTB during the development of the Planck scale will benefit the economy in general and strengthen the leading position of the German scale industry throughout the world.

While PTB is considering the practical outcomes and opportunities of the redefinition of the kilogram, the redefinition itself is not yet complete. As one of the world's leading metrology institutes, PTB is playing a major role in this redefinition as well. Two experiments are being pursued internationally in order to achieve the goal of defining the kilogram in such a way that it is based on of natural constants: the Avogadro experiment, which will determine the number of atoms in an almost perfectly spherical crystal made of isotopically pure silicon; and the Kibble balance (or watt balance), in which the gravitational force of a mass in the Earth's gravitational field is compensated by an . Because both experiments determine the value of Planck's constant, both approaches fulfill the goal mentioned above. Whereas PTB's approach is primarily via the silicon sphere, the Kibble balance is favored by NIST in the United States and NRC in Canada. However, in order to be able to offer both approaches for the future dissemination of mass units to industry, PTB - together with TU Ilmenau - has initiated prototype development for a Planck scale (as a version of the Kibble balance that is suited for industry).

The Institute of Process Measurement and Sensor Technology at TU Ilmenau, which is jointly contributing to the development of the Planck scale under the scientific direction of Professor Thomas Fröhlich, is an internationally leading institution in the fields of industrial force-measurement technology, weighing technology and nanometer-precision laser metrology. Over the past ten years, measuring instruments were developed at TU Ilmenau that were considered the "most accurate scale in the world". The knowledge gained from the development of a so-called 1-kg prototype comparator was directly incorporated into the research on the Planck scale. This highly accurate mass comparator is already being used at national metrology institutes throughout the world to compare kilogram prototypes.

Explore further: Researchers developing a new balance for the new kilogram

Related Stories

Researchers developing a new balance for the new kilogram

June 20, 2017

Technische Universität Ilmenau and the Physikalisch-Technische Bundesanstalt (the National Metrology Institute of Germany) are developing a balance which is required for measuring the redefined kilogram that will be introduced ...

Redefining the kilogram at NPL

July 27, 2016

Researchers from the National Physical Laboratory (NPL) are working with scientists across the globe to redefine the SI unit of mass, the kilogram, as part of a major revision of the SI base units. NPL has recently published ...

Important milestone reached on road to a redefined kilogram

June 21, 2016

In a secure vault in the suburbs of Paris, an egg-sized cylinder of metal sits in a climate-controlled room under three glass bell jars. It is the mass against which all other masses in the world are measured - by definition ...

Defect-free coatings for silicon spheres

July 4, 2017

The prototype kilogram – to which all scales are calibrated to – is losing weight. International efforts are striving to redefine the base unit for measuring mass and, in future, redefine the kilogram on natural constants. ...

Kilogram celebrates its 125th birthday

September 25, 2014

The IPK has been the global standard for mass for the last 125 years; it was sanctioned at the first General Conference on Weights and Measures (CGPM) on 7-9 September 1889 in Paris. This is likely to be the last landmark ...

Recommended for you

Lightning, with a chance of antimatter

November 22, 2017

A storm system approaches: the sky darkens, and the low rumble of thunder echoes from the horizon. Then without warning... Flash! Crash!—lightning has struck.

How the Earth stops high-energy neutrinos in their tracks

November 22, 2017

Neutrinos are abundant subatomic particles that are famous for passing through anything and everything, only very rarely interacting with matter. About 100 trillion neutrinos pass through your body every second. Now, scientists ...

Quantum internet goes hybrid

November 22, 2017

In a recent study published in Nature, ICFO researchers led by ICREA Prof. Hugues de Riedmatten report an elementary "hybrid" quantum network link and demonstrate photonic quantum communication between two distinct quantum ...

Enhancing the quantum sensing capabilities of diamond

November 22, 2017

Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.