Description: The Joule balance is a precision instrument designed to measure the Planck constant, which in turn allows for the definition of the kilogram in terms of fundamental units of physics. This device is based on the relationship between energy and the frequency of electromagnetic radiation, making it a crucial tool in the field of modern metrology. The Joule balance operates by comparing forces, using a system of weights and a mechanism that allows for highly accurate measurements. Its importance lies in providing a way to measure mass that aligns with universal physical constants, which is essential for scientific research and industry. The Joule balance is not only an advancement in metrology but also represents a shift in how we understand and define units of measurement, making them more coherent and precise in a global context.
History: The Joule balance was developed in the context of the redefinition of the kilogram, which took place in 2019 during the General Conference on Weights and Measures. Before this redefinition, the kilogram was based on a physical object, the ‘kilogram prototype,’ which was susceptible to changes in mass. The need for a more stable and universal definition led to the adoption of the Planck constant as the basis for the definition of the kilogram, and the Joule balance became a key instrument for making these measurements.
Uses: The Joule balance is primarily used in metrology laboratories to establish and verify the mass of objects in relation to the Planck constant. This is essential for ensuring accuracy in mass measurement across various scientific and industrial applications. Additionally, it is employed in research to explore physical properties and in the calibration of other measuring instruments.
Examples: A practical example of the use of the Joule balance is at the National Metrology Laboratory of France, where it is used to make precise measurements that help define the kilogram in terms of the Planck constant. Another example is its application in research for new technologies that require extremely accurate mass measurements, such as in the manufacturing of electronic components.
