Probe Box Property
Probes are useful to record voltages, currents, field strengths or waveguide mode amplitudes at certain points in space. Adding a probe in openEMS is a two stage process. Firstly a probe property is added to the CSX structure with the help of AddProbe and at least one primitive. If there is only one primitive, a text file with the name of the property is written. If there are several primitives, they are numbered consecutively and files with "propertyName_n" are written where n is the number of the primitive. The text file can later be read with ReadUI in the case of voltages or currents when the openEMS job has finished.
When a frequency array is provided via the Frequency key, a text file "propertyName_FD" is also written. This file contains the Fourier transformed quantity at the given frequencies.
The appropriate primitive depends on the observable to be recorded. For a (non-retarded?) voltage, a straigt line (e.g. an AddWire with two end points and zero radius) would be appropriate. The result will be the voltage between those two end poins. For a current probe, a two-dimensional shape is appropriate (e.g. an AddBox with zero extent in one dimension.
Field quantities (E and H) can also be read with ReadUI. However, in this case the structure delivered by ReadUI needs to be treated specially because these are vectors. For those quantities only the start coordinate of the primitive (e.g. a box) is used for the definition of the location of the probe.