Terminal

The node provides a boundary or domain condition for connection to external circuits, to transmission lines, or with a specified voltage or charge. By specifying zero charge, a floating potential condition is obtained.


	In most cases, it is not recommended to include the interior of good conductors in the simulation. When using the Terminal on the domain level, the interior unknowns for the electric potential are automatically replaced by a single constant, thus avoiding numerical problems arising from a very high material contrast. If one instead uses the Terminal on the boundary level, it is recommended to exclude the interior of the associated conductor from the domain selection for the main Electrostatics node.

The node also enables the computation of the lumped parameters of the system, such as capacitance. See Lumped Parameters.

Terminal

Specify the terminal properties. Enter a unique that will be used to identify the global variables (such as the terminal voltage or current) that are defined by the terminal. The can contain alphanumeric characters, but it should be numeric when performing terminal sweeps.

Select a — (the default), , , or . Select:

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to prescribe the total charge deposited on the terminal boundaries. Enter the total charge Q0. The default is 0 C, which corresponds to a uncharged floating electrode.

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to specify a fixed electric potential at the terminal. Enter an electric potential V0. The default is 1 V.


	To correctly calculate the terminal charge and the corresponding capacitances, if Voltage Terminal is used on boundaries between The Electrostatics Interface and The Electrostatics, Boundary Elements Interface, let the dependent variable for The Electrostatics, Boundary Elements Interface be the same as the dependent variable for The Electrostatics Interface and disable Electric Scalar-Scalar Potential Coupling. How to set the name for the dependent variable is described in the Dependent Variables section. Since the Electric Scalar-Scalar Potential Coupling is disabled, add manually a Fully Coupled node to the Stationary Solver below the Solution node in the Solver Configurations.

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to specify a terminal connected to an Electrical Circuit physics interface that models an external circuit. The Terminal node provides a current-voltage characteristic to the circuit.


	The Electrical Circuit Interface requires a current from the Terminal, so the Circuit terminal type can only be used in Time Dependent or Frequency Domain studies, in which the current can be computed as the time derivative of the charge. The Circuit type cannot be used together with a terminal sweep.

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to connect the terminal to an impedance that might represent a load or a transmission line. When is selected, the scattering parameters (S-parameters) are computed. The setting can only be used in frequency-domain studies.

Enter a P0 to specify the input power at this terminal from the transmission line. This excitation can be toggled using a port sweep.

Select an option from the list to define the value of the impedance — or . For i the Zref defined on the window for the physics under Sweep Settings is used. For enter a specific impedance Zref for this terminal. The default is 50 Ω.

Initial values

The initial values subsection is used to provide initial values for the internal state variables in the Terminal. These settings can be useful to provide an initial guess to the nonlinear solver or the initial value in a time-dependent study.

The is available for all Terminal types except Voltage. Enter an Vinit.

The is available for the Circuit excitation. It specifies the initial charge on the terminal when the circuit is connected. Enter an Qinit.

Constraint Settings

To display this section, click the button (

) and select in the dialog box.


	Studies and Solvers in the COMSOL Multiphysics Reference Manual


	For a voltage terminal type example, see Dielectric Shielding Comparison: Application Library path ACDC_Module/Capacitive_Devices/dielectric_shielding_comparison.