Watt balance

Watt balance

The watt balance is an experimental electromechanical apparatus that may one day provide a definition of the kilogram based on electronics.

The watt balance is a more accurate version of the ampere balance, in which the force between two current-carrying coils is measured and then used to calculate the magnitude of the current. The principle of the watt balance was proposed by B. P. Kibble of the UK's National Physical Laboratory (NPL) in 1975.

The main weakness of the ampere balance method is that the result depends on the accuracy with which the dimensions of the coils are measured. The watt balance method has an extra calibration step in which the effect of the geometry of the coils is eliminated, removing the main source of uncertainty. This extra step involves moving the force coil through a known magnetic flux at a known speed.

The present accuracy record is held by NIST, the standards agency of the USA, with an error of 5.2 × 10-8, and experiments are continuing towards a goal of 1 × 10-8. The long-term goal of these experiments is to produce a new definition of the kilogram based on fundamental SI units, to replace the present definition based on the International Prototype Kilogram, a cylinder of platinum/iridium owned by the International Bureau of Weights and Measures.

External links

* [http://www.iop.org/EJ/abstract/0026-1394/42/5/014 R. Steiner, E.R. Williams, D.B. Newell and R. Liu. "Towards an electronic kilogram: an improved measurement of the Planck constant and electron mass." "Metrologia." (October 2005)]
* [http://nvl.nist.gov/pub/nistpubs/jres/106/4/j64schw.pdf Joshua P. Schwarz, Ruimin Liu, David B. Newell, Richard L. Steiner, Edwin R. Williams, Douglas Smith "Hysteresis and Related Error Mechanisms in the NIST Watt Balance Experiment" (August 2001)]
* [http://www.bipm.fr/en/scientific/elec/watt_balance/ Bureau International des Poids et Mesures]
* [http://www-optics.unine.ch/former/metrology/Watt_balance/Watt_balance.html Swiss Federal Office of Metrology]


Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Watt (disambiguation) — Watt may refer to:*Watt, the SI (Système International) unit of power, named for James Watt, which has several associated measures or quantities: **Watt hour **Watt balance **Nominal watt *Watt (novel), a book by Samuel Beckett *Watt (album), by… …   Wikipedia

  • Watt-Waage — Die Watt Waage ist eine Präzisionswaage, mit der zukünftig das Kilogramm definiert werden könnte, indem dem Planckschen Wirkungsquantum ein fester Zahlenwert gegeben wird. Inhaltsverzeichnis 1 Hintergrund 2 Messprinzip 3 Experimentelles …   Deutsch Wikipedia

  • Watt — For other uses, see Watt (disambiguation). Kilowatt redirects here. For the community in Kern County, California, see Kilowatt, California. KW redirects here. For other uses, see KW (disambiguation). The watt (pronounced /ˈwɒt/ wot; symbol: W) is …   Wikipedia

  • Balance Du Watt — Pour les articles homonymes, voir balance. La balance du watt est un appareil qui permet de convertir, avec neuf chiffres significatifs, la puissance mécanique en puissance électrique et vice versa La longueur et le temps étant définis, il… …   Wikipédia en Français

  • Balance du Watt — Pour les articles homonymes, voir balance. La balance du watt est un appareil qui permet de convertir, avec neuf chiffres significatifs, la puissance mécanique en puissance électrique et vice versa La longueur et le temps étant définis, il… …   Wikipédia en Français

  • Balance du watt — Pour les articles homonymes, voir balance. Balance du watt du National Institute of Standards and Technology. Le dôme qui descend autour de la balance lors de la mise sous vide est visible au dessus …   Wikipédia en Français

  • Balance — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Sur les autres projets Wikimedia : « balance », sur le Wiktionnaire (dictionnaire universel) Sommaire …   Wikipédia en Français

  • Ampere balance — The ampere balance The ampere balance (also current balance or Kelvin balance) is an electromechanical apparatus used for the precise measurement of the SI unit of electric current, the ampere. It was invented by William Thomson, 1st Baron Kelvin …   Wikipedia

  • William Watt — Infobox Premier honorific prefix = The Right Honourable name=William Watt honorific suffix = PC nationality =Australian order =24th Premier of Victoria term start =18 May 1912 term end =9 December 1913 term start2 =22 December 1913 term end2 =18… …   Wikipedia

  • Price per watt — Price per watt, or $/W is a common way to compare the capital costs of various forms of electricity generation. It refers to the number of dollars one would have to spend to buy a machine capable of producing one watt of electricity. It is… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”