Watt within the then-existing system of practical units as "the power conveyed by a current of an Ampère through the difference of potential of a Volt." In October 1908, at the International Conference on Electric Units and Standards in London, so-called "international" definitions were established for practical electrical units. Siemens' definition was adopted as the "international" watt. (Also used: 1 ampere x 1 ohm.) The watt was defined as equal to 10 units of power in the "practical system" of units. The "international units" were dominant from 1909 until 1948. After the 9th General Conference on Weights and Measures in 1948,
Ampere balance from 1 to 100 centi-amperes, the deci-ampere balance from 1 to 100 deci-amperes, the ampere balance from 1 to 100 amperes, etc. 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. The current to be measured is passed in series through two coils of wire, one of which is attached to one arm of a sensitive balance. The magnetic force between the two coils is measured by the amount of weight