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Current issue

ELEKTRO 12/2017 was released on December 6th 2017. Its digital version will be available on January 5th 2018.

Topic: Measurement, measuring devices and engineering; Testing and diagnostics

Main Article
Measurements on rotating machines using SFRA method
Application possibilities of ultra-capacitors or LiFePO4 batteries in trolley network of the Brno Public Transit Company

SVĚTLO (Light) 6/2017 was released on December 11th 2017. Its digital version will be available on january 11th 2018.

Lighting installations
The lighting of university building Centrale Supélec in Saclay in France
The light for our future

Daylight
Application and judgment light guides Solatube®

Important milestone reached on road to a redefined kilogram

22.06.2016 | NIST | www.nist.gov

A high-tech version of an old-fashioned balance scale at the National Institute of Standards and Technology (NIST) has just brought scientists a critical step closer toward a new and improved definition of the kilogram.

The scale, called the NIST-4 watt balance, has conducted its first measurement of a fundamental physical quantity called Planck’s constant (called h) to within 34 parts per billion – demonstrating the scale is accurate enough to assist the international community with the redefinition of the kilogram, an event slated for 2018.

New measurement of kilogram

The redefinition–which is not intended to alter the value of the kilogram’s mass, but rather to define it in terms of unchanging fundamental constants of nature–will have little noticeable effect on everyday life. But it will remove a nagging uncertainty in the official kilogram’s mass, owing to its potential to change slightly in value over time, such as when someone touches the metal artifact that currently defines it.

Accurate measurement of Planck’s constant is the key to retiring the physical kilogram, because it provides a way to equate mass with a particular amount of electric energy, which can be expressed as a function of h. If we know h precisely, we can build an electromagnet and measure exactly the amount of electric current it needs to lift a kilogram off the ground, and define the kilogram in terms of the current. Scientists are putting this idea to work in a device called the watt balance, which compares a physical mass with finely measured amounts of electricity.

Read more at NIST

Image Credit: NIST

-jk-