The International System of Quantities (ISQ) consists of the quantities used in physics and overall evolving new fields in modern science and technology. It is the system of quantities underlying the International System of Units (SI) but does not determine the units of measurement used for the quantities. This system is inherently incomplete because the number of quantities is potentially infinite. The ISQ is formally described in ISO 80000-1:2022- Quantities And Units – Part 1: General.
What Is ISO 80000-1:2022?
ISO 80000-1:2022 provides general information concerning quantities, systems of quantities, units, quantity and unit symbols, and coherent unit systems. It further specifies printing rules, rules for terms in names for physical quantities, rounding of numbers, and logarithmic quantities. The standard specifically highlights the International System of Quantities (ISQ), in which there are seven base quantities:
- Length
- Mass
- Time
- Electric current
- Thermodynamic temperature
- Amount of substance
- Luminous intensity
ISO 80000-1:2022 serves as a guide for the use of physical quantities and units of measurements. The standard is intended for general use within the various fields of science and technology. It specifically is used by authors writing scientific and engineering journals and in these authors’ conference papers and corresponding books—especially textbooks. ISO 80000-1:2022 serves as an introduction to other parts of the ISO/IEC 80000 for the ISQ. The ISO/IEC 80000 series does not, as yet, cover ordinal quantities and nominal properties.
What Are Quantities in ISO 80000-1:2022?
Quantity refers to both general quantities, such as length, mass, etc., and their instances, such as given lengths, given masses, etc. For example, both that length is a quantity and that a given length is a quantity.
Quantities are comparable when they are the same kind and instances of the same general quantity. For example, diameters and heights are quantities of the same kind, being instances of the general quantity length.
What Are the System of Quantities in ISO 80000-1:2022?
A set of quantities and their relations are called a system of quantities. General quantities are related through equations that express laws of nature or define new general quantities. Here are some examples of the application of the system of quantities:
- Based quantities are quantities of different kinds that are thought of as mutually independent. It is a matter of choice how many and which quantities are considered to be base quantities.
- Derived quantities are defined or expressed in terms of base quantities by means of equations. It is a matter of choice which equations are used to define the derived quantities.
- Equations between quantities sometimes contain constant multipliers. These multipliers depend on the definitions chosen for the quantities occurring in the equations, i.e., on the system of quantities chosen. Such multipliers may be purely numerical and are called numerical factors.
What Are Units in ISO 80000-1:2022?
The unit is a reference quantity. When the unit is chosen, any other quantity of the same kind can be expressed in terms of this unit as a product of this unit and a number. That number is called the numerical value of the quantity expressed in this unit. For example, quantities that are of the same kind (e.g., length) have the same dimension, even if they are originally expressed in different units (such as yards and meters).
What Is a Coherent System in ISO 80000-1:2022?
In a coherent system of units, the expression of each unit corresponds to the dimension of the quantity in question. This means that the expression of the unit is obtained by replacing the symbols for base dimensions in the quantity dimension by those for the base units, respectively. In such a coherent system of units, no numerical factor other than 1 ever occurs in the expressions for the derived units in terms of the base units.
What Are the 13 Parts of ISO/IEC 80000?
- General
- Mathematics
- Space and Time
- Mechanics
- Thermodynamics
- Electromagnetism
- Light and Radiation
- Acoustics
- Physical Chemistry and Molecular Physics
- Atomic and Nuclear Physics
- Characteristic Numbers
- Condensed Matter Physics
- Information Science and Technology
ISO 80000-1:2022- Quantities And Units – Part 1: General is available on the ANSI Webstore.