The QuantityType defines a model for physical quantities. These are listed in the Quantites Folder. Each quantity has a ServerUnits Folder in which the units, referenced by EngineeringUnit Properties with HasEngineeringUnitDetails, are listed. Each ServerUnit can have a list of alternative units to which the Variable value can be converted.

Figure 8 - QuantityType

It is illustrated in Figure 8 and formally defined in Table 36.

Table 36 – QuantityType definition

Attribute	Value
BrowseName	QuantityType
IsAbstract	False
References	NodeClass	BrowseName	DataType	TypeDefinition	Other
Subtype of the BaseObjectType defined in OPC 10000-5
HasProperty	Variable	Symbol	LocalizedText	PropertyType	O
HasProperty	Variable	Description	LocalizedText	PropertyType	O
HasProperty	Variable	Annotation	AnnotationDataType[]	PropertyType	O
HasProperty	Variable	ConversionService	UriString	PropertyType	O
HasProperty	Variable	Dimension	QuantityDimension	PropertyType	M
HasComponent	Object	ServerUnits		BaseObjectType	M
Conformance Units
Data Access Quantities Base

The DisplayName Attribute of each instance shall provide the name of the quantity, e.g. “acceleration”, “battery capacity” or “pressure in relation to volume flow rate”.

The Symbol Property is used for the symbol of the quantity (e.g. ‘l’ for length, ‘t’ for time, or ‘T’ for temperature).

The Description Property is used to expose a more verbose explanation.

Annotation allows naming annotations for a physical quantity. These Annotations are explanations of the physical quantity such as "relative" for a relative velocity. The AnnotationDataType is described in chapter 6.6.1.

For example a VAC RMS measurement is the quadratic mean measurement of an AC voltage. We are using two annotation elements to represent it. Its Instance would contain the following values:

Annotation	Discipline	uri
AC	Electrical Engineering	https://www.britannica.com/science/alternating-current
RMS	Electrical Engineering	https://en.wikipedia.org/wiki/Root_mean_square)

ConversionService allows to name an external conversion service for the unit in which the client can have a conversion to a target unit performed.

Dimension describes the dimension of a physical quantity in power representation. Its DataType is described in chapter 6.6.4.

ServerUnits allows listing ServerUnits for a physical quantity. The ServerUnits are of ServerUnitType which is described in chapter 6.4.2.

Syntax References: Instances of the QuantityType can identify the physical quantity in a specific external reference work using HasDictionaryEntry References – see 6.3.2.

The components of the QuantityType have additional subcomponents which are defined in Table 37.

Table 37 – QuantityType Additional Subcomponents

BrowsePath	References	NodeClass	BrowseName	DataType	TypeDefinition	Others
ServerUnits	HasComponent	Object	<ServerUnit>		ServerUnitType	MP