Ansys Insight : How close can monitors be to other objects?

kchowkchow Ansys Employee Posts: 2
edited February 23 in Photonics

In FDTD simulations, each field components is calculated at different spatial location within the mesh cell. This can lead to confusion about where it is valid to put monitors, when they are close to other objects. For example, can a time monitor be right at the edge of the simulation region, or does it need to be a few mesh points away from the boundary?

This section describes how close monitors can be to other objects.





Structures do not interfere with monitors. It is ok to have a monitor at the interface of two structures, or have a monitor cross through several objects. However, there are some types of calculations (like far field projections) that require the monitor to be in a homogeneous material. In this case, the monitor should be at least one full mesh point away from the structures.

Simulation region

The simulation boundary conditions are applied just past the inner edge of the simulation region boundary (the thick orange line). It is ok to have a monitor exactly at the inner edge of the simulation region boundary. Any monitors that extend beyond the inner edge will be automatically truncated at this edge.


Sources require a certain amount of space to inject the fields (2-3 mesh cells). Within this region, the fields are not physically meaningful. Therefore, monitors should not be placed within this region. Sources graphically depict this region with light grey shading. The following screenshot shows the injection region of the source, and two monitors. The time monitor is too close the the source whereas the profile monitor is in a valid location.


Monitors do not interfere with other monitors. It is ok to have multiple monitors in the same position.


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