A WEIGHTY HISTORY
Late 19th Century
The galvanometer is used to measure the ampere, the International System of Units (SI) unit of electric current, but its measurements lack precision.
1970 to 1978
Bryan Kibble proposes a new method allowing for very accurate measurements of the ampere and makes the first Kibble balance.
Setting of the conventional values of the von Klitzing and Josephson constants, which are used throughout the world for voltage and resistance calibration. Bryan Kibble and Ian Robinson invent the Kibble Mark II balance, which uses a circular coil and operates in vacuum conditions.
The NRC successfully takes over the MKII balance project to measure the kilogram. Researchers Barry Wood and Carlos Sanchez work with Ian Robinson to set up the balance to gain a better understanding of how it works.
The NRC refurbishes building M-34 to house the Kibble balance experiment, and the balance arrives at the end of the year.
The Kibble balance is constructed, assembled, evaluated and calibrated, and software is developed to interface with the apparatus.
The NRC performs a trial measurement and devotes the year to correcting a systemic error attributable to mass exchange.
Improvement of the modelling of the alignment of the Kibble balance, as well as gravity determinations and profiling. Four Planck constant determinations are made, resulting in the most accurate values ever reported.
2014 to 2016
Improvements are made to the balance and yield three new and increasingly accurate Planck constant determinations. The International Committee for Weights and Measures (CIPM) recommends that watt balance projects be referred to as "Kibble balance projects" in honour of Bryan Kibble.
April • The Committee on Data for Science and Technology includes the NRC's value of the Planck constant in its special adjustment for redefinition of the SI. This value has the smallest uncertainty and the most "weight" of any result in setting the final value of the Planck constant.
THE VALUE OF PLANCK'S CONSTANT CAN BE SET FOREVER!