Why can I not connect two components?

Incompatible submodels

When you try to connect two components, you may get the following error message even if the ports have compatible types:

Figure 393: Example of components that cannot be connected

This happens when no compatible combination of Submodel submodels exists between these two components. Components and lines are associated with submodels which produce and require quantities that are exchanged with other submodels. These quantities are called external variables:

• External variables produced by a submodel are called Output outputs.

• External variables required by a submodel are called inputs Input external variables required by a submodel .

• The main function of a submodel is to calculate its outputs from its inputs.

Two submodels are compatible when each one receives the inputs it requires from the other.

In order to display the external variables of a submodel associated with a component or line:

1. Right-click on this object and select the External variables External variables item of the menu.

If a submodel is already attached to the object, you will get the External Variables dialog box directly:

If no submodel is attached to the object, you will get a Show Details dialog box. You can then select the submodel for which you want to check the external variables:

2. Select a submodel, then click on the External variables button:

Looking at the external variables of two components is very useful when trying to understand why you cannot connect them together. You will always find that at least one input of at least one component is not supplied by the other:

Figure 394: A mass will connect to spring but not to another mass

You can open the Help page corresponding to the submodel directly from the External Variables dialog box:

Figure 395: Opening the Help

Figure 396: Submodel help