The kelvin (K) is the unit of thermodynamic temperature.

The ampere (A) is the unit of electric current.

In addition to the unit one, the SI defines 7 base units and associated symbols: It is the neutral element of any system of units. The unit one (1) is the unit of a quantity of dimension one. In its most restrictive interpretation, this is what may be meant when the term metric unit is used. The first group of metric units are those that are at present defined as units within the International System of Units (SI).

Main article: International System of Units MKS system of units (metre, kilogram, second).Metre–tonne–second (MTS) system of units.International System of Electrical and Magnetic Units.Other unit systems using metric units include: By extension they include units of electromagnetism from the CGS and SI units systems, and other units for which use of SI prefixes has become the norm. The most widely used examples are the units of the International System of Units (SI). Instead, metric units use multiplier prefixes that magnifies or diminishes the value of the unit by powers of ten.' Metric units are in general based on reproducible natural phenomena and are usually not part of a system of comparable units with different magnitudes, especially not if the ratios of these units are not powers of 10. According to Schadow and McDonald, metric units, in general, are those units 'defined 'in the spirit' of the metric system, that emerged in France of the 18th century and was rapidly adopted by scientists. The frequency of 540 THz resembles a wavelength of about 556 nanometers (nm), which is in the middle of the visible-light spectrum.Metric units are units based on the metre, gram or second and decimal (power of ten) multiples or sub-multiples of these. The EM-field power level of 1.46 x 10 -3 W is too small. To some professionals the CGPM specifications are unclear. According to the CIE, the human eye is most sensitive to the green frequency. The frequency chosen in the optical spectrum that is visible to the human eye is near the color green. One foot-candle is equal to one lumen per square foot. Foot-candle: This is the light level on a surface one foot from a standard candle.(The Germans, Austrians and Scandinavians used the Hefner lamp with 1.128 hefnerkerze equal to 1.019 candela.)

Candlepower: This is used by the English and is the light produced by a spermaceti (wax from a sperm whale) candle weighing one sixth of a pound and burning at a rate of 120 grains per hour.Prior to 1948, luminous intensity was generally measured by the brightness of the flame from a “standard candle.” These terms are defined as follows: The older term for candela is candle, such as foot-candle and candlepower. It is standardized by the International Commission on Illumination (CIE) and can be used to convert radiant energy into luminous. The luminosity function is the average visual sensitivity of the human eye to diverse wavelengths. Candela is defined by the CGPM as the level of an electromagnetic field, in a specified direction, with 1/683 watt (1.46 x 10 -3 W) per steradian and frequency of 540 terahertz.

Candela unit of measurement