In addition, the PTB will provide the "new" Kelvin in the building: From May 20 this year, the SI base unit
of temperature, the Kelvin, will no longer be above the triple point of water, but over a constant of nature, the Boltzmann Constant, defined.
This idea had to be abandoned because the path to an SI base unit
adopted by the CGPM was too narrow, considering that there are only seven base units.
A good example of an experiment developed to realize the SI base unit
of current is the ampere balance .
Since the kilogram is the last artifact SI base unit
defined in terms of a material artifact, a quantum standard of mass founded on electrical measurements would complete the modern trend of removing all artifacts from the definitions of SI units.
The kilogram is one of the seven SI base units
from which all other units can be derived and is the only one which is measured against a physical object - the IPK - all others are standardised against known constants.
The definitions of the current SI base units in Secs.
In it, Feller points out the dependence of five of the SI base units on fundamental constants.
The current SI is founded on the seven base quantities, assumed to be independent, time, length, mass, electric current, thermodynamic temperature, amount of substance, and luminous intensity, for which the SI base units are the second s, meter m, kilogram kg, ampere A, kelvin K, mole mol, and candela cd, respectively; see Table 1.
A calibrator that uses the International System of Units (SI base units) of time and length to derive gas flow measurements can be considered primary technology.
The seven SI base units are length, time, mass, electric current, thermodynamic temperature, amount of substance, and luminous intensity.
Thus, the working principles of DryCal technology use the SI base units of time and length to calculate gas flow, making it one of the only primary technologies on the market.
I also took into account the fact that not all of NIST's work can be neatly categorized by SI base units
and the measurements associated with them.