|The Capacity Calculator calculates the capacity between any impedance-controlled net (or part thereof) and the associated ground or reference net. The basic assumption is that high-frequency nets should lie one above the other to ensure signal integrity. For the calculation, PCB-Investigator applies the formula of the plate capacitor for each of the overlapping areas.|
If you want to determine the capacity of any net, open the Capacity Calculator (analysis tab/ high speed).
Frst, you have to select a net (1) and the corresponding ground net (2). This can either be done using the list selection or by selecting directly using the tool. To confirm the selection made in the tool, press the following button . If one of your nets has a "GND" or equivalent in its name, it is assumed to be the ground net. It will be pre-selected as ground.
In order to run the calculation, the layer structure must be entered correctly. For more information, please refer to Layer Matrix menu.
Furthermore Epsilon must be defined. More information, how to determine this value can be found under "Example: Definition of Epsilon". If you want to change the default settings or if you haven´t predefined the value for the corresponding layer, go to Options (3) or Settings and change the value as required.
Finally, you can calculate the capacity by clicking on the button "Calculate" (4). For this purpose, you will be given a single value for each individual overlap (5). The total capacity is the sum of the individual overlaps (see sketch).
Example of a result that contains overlaps (as indicated in the sketch).