The units of structural features (such as Value Properties, Flow Properties, Constraint Parameters, etc.) that are connected through a Binding Connector can be automatically converted. The units are converted only if both sides have a compatible set of units of the same quantity kind. If the conversion fails due to incompatible units, the values are mirrored the same as with the Auto Convert Units option disabled.



The units can be loaded through the ISO 80000 library and ISO 80000 extension. To learn more about how to load and apply units, refer to Using Units.

Unit conversion is performed according to the SysML extension QUDV. You can also create your own units or whole library based on the QUDV standard. To learn more about the QUDV library, refer to the QUDV library. 

The supported unit types in the QUDV library include:

  • PrefixedUnit (e.g., kilogram)
  • LinearConversionUnit (e.g., inch)
  • AffineConversionUnit (e.g., Fahrenheit)
  • DerivedUnit (e.g., km/h)

  • SimpleUnit (base unit, eg., gram)

You can use different kinds of units for different structural features based on the usage and domain. The following example shows that basic SI units are set on Constraint Parameters and imperial units are set on Value Properties.


SI units and imperial units used in one Parametric Diagram

Units are converted according to the definitions (or values) set in the Unit element. For linear conversion units, the most important aspects are factor and referenceUnit.


Unit pound Specification dialog

Enabling or disabling the Auto Convert Units option

To enable or disable the Auto Convert Units option in the Project Options dialog

  • In the Project Options dialog, set the Auto Convert Units property value to true to enable the functionality or false to disable the functionality.



To enable or disable the Auto Convert Units option in the Simulation Configuration Specification dialog

  • In the Simulation Configuration Specification dialog, set the Auto Convert Units property value to true to enable the functionality or false to disable the functionality.



  • The Auto Convert Units option is enabled by default for the project. The Auto Convert Units option is disabled by default for the projects saved with versions previous to the 2024x version.
  • The Auto Convert Units option in the Simulation Configuration Specification dialog is only visible with the Expert mode.
  • The simulation properties set in the Simulation Configuration supersede the ones set in the Project Options dialog.

The Transmission sample uses unit conversion in its Parametric Diagram.