Enhetstypen

Enhetstypen, or the unit type in Swedish usage, is a categorization used to group units that measure the same kind of physical quantity. Each unit type defines the nature of the quantity being measured and determines which units can be used interchangeably for measurement, comparison, and conversion. Unit types are distinct from individual units; for example, length is a unit type, while meter and kilometer are units within that type.

Unit types can be organized into base quantities and derived quantities. Base quantities, such as length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity, are the fundamental dimensions. Derived quantities, such as velocity, area, energy, and force, arise from combinations of base quantities. In the International System of Units (SI), seven base unit types define the core dimensions, and a wide range of derived unit types cover practical measurements. Each unit type has associated units that share the same dimension and can be converted using a predefined conversion factor, while preserving dimensional consistency.

In data modelling, enhetstypen is used to enforce validity and enable automatic unit conversion. Software systems often represent a quantity by its unit type plus a specific unit, and may validate that operations involve compatible types. Standards and ontologies such as QUDT (Quantity, Unit, Dimension) and ISO 80000 provide formal definitions for unit types and their relationships, supporting interoperability.

Common challenges include handling non-SI units, offset conversions (for example Celsius to Kelvin), and dimensionless quantities like angles. Understanding enhetstypen helps ensure accurate measurement, computation, and data exchange across disciplines.