SENSE follows the method that is described in detail here, Maxwell Capacitance Matrix, to perform the necessary simulations and extract the Capacitance values of a sensor.
In short, this paper describes the following:
In a system of 4 conductors, the capacitance values are shown below.
Cii values represent the self capacitance towards the infinite earth, whereas Cij values represent the mutual capacitance between the conductors. The (-) sign is a convention representing the mutual capacitance values well established in the literature.
Those capacitance values are represented in a capacitance matrix as below. In the first row we have the 1st cell showing the sum of all capacitance values on the 1st conductor, the 2nd cell showing the mutual capacitance towards the 2nd conductor, the 3rd cell showing the mutual capacitance towards the 3rd conductor and the 4th cell showing the mutual capacitance towards the 4th conductor. The same holds for the 2nd, 3rd and 4th rows, respectively.
The sum of the capacitance values of each conductor (the diagonal cells above) represent the Self Capacitance of this conductor, that is also printed in SENSE's results and this is the value that is used by the industry and literature.
Cji and Cij values should be equal, since they represent the same mutual capacitance (from j to i and from i to j respectively). However, some small discrepancies should exist due to numerical functions.
SENSE represents the results in the same manner.