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Two same conductors have different self-capacitanc

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[quote][i]Originally posted by Rio[/i]
[br]Hi all,
I really need some help here. I have two square conductors (same shape and put parallel to each other) and I calculate their capacitance matrix and got the following thing:

CAPACITANCE MATRIX, picofarads
                   1          2 
1%GROUP1 1      292.2     -93.49
1%GROUP2 2     -93.49        103

I expect the two self-capacitanc to be the same value but they are not. I do not think the code has anything wrong but I attach it here. I really can not understand this why so I ask for help here. Anybody knows what happened?

The code is attached:

*This file is Square_5_0_0.lst
*Test geometry to show the self/mutual capacitance between 1x1 bus conductors
* FastCap2 surface list file for two parallel conductors
* Both of the two are consisted with the back_left surface, the back_right surface and the bottom surface
* The first conductor
* The two side surfaces
C back_left.qui 1 0 0 0 +
C back_left.qui 1 0 1 0 +
C back_left.qui 1 5 0 0 +
C back_left.qui 1 5 1 0 +
C back_left.qui 1 1 0 0 +
C back_left.qui 1 1 1 0 +
C back_left.qui 1 6 0 0 +
C back_left.qui 1 6 1 0 +
C back_left.qui 1 2 0 0 +
C back_left.qui 1 2 1 0 +
C back_left.qui 1 7 0 0 +
C back_left.qui 1 7 1 0 +
C back_left.qui 1 3 0 0 +
C back_left.qui 1 3 1 0 +
C back_left.qui 1 8 0 0 +
C back_left.qui 1 8 1 0 +
* The bottom abd the top surfaces
C bottom.qui 1 0 0 0 +
C bottom.qui 1 0 0 1 +
C bottom.qui 1 5 0 0 +
C bottom.qui 1 5 0 1 +
C bottom.qui 1 1 0 0 +
C bottom.qui 1 1 0 1 +
C bottom.qui 1 6 0 0 +
C bottom.qui 1 6 0 1 +
C bottom.qui 1 2 0 0 +
C bottom.qui 1 2 0 1 +
C bottom.qui 1 7 0 0 +
C bottom.qui 1 7 0 1 +
C bottom.qui 1 3 0 0 +
C bottom.qui 1 3 0 1 +
C bottom.qui 1 8 0 0 +
C bottom.qui 1 8 0 1 +
* The front and the back surfaces
C back_right.qui 1 0 0 0 +
C back_right.qui 1 5 0 0 +
C back_right.qui 1 4 0 0
C back_right.qui 1 9 0 0

0 1mX1mX1m cube (n=3 e=0.1)
* xo = 0, yo = 0, zo = 0
* view from -x -y +z
* This is the square-plane on x-z plane
*
* back left
Q 1 1.00000e+000 0.00000e+000 0.00000e+000 1.00000e+000 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 0.00000e+000
Q 1 9.16667e-001 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 0.00000e+000
Q 1 8.33333e-002 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 8.33333e-002 2.77556e-017 0.00000e+000 8.33333e-002 2.77556e-017 0.00000e+000 0.00000e+000
Q 1 1.00000e+000 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 8.33333e-002
Q 1 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 8.33333e-002
Q 1 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 9.16667e-001 2.77556e-017 0.00000e+000 9.16667e-001 2.77556e-017 0.00000e+000 8.33333e-002
Q 1 1.00000e+000 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 9.16667e-001
Q 1 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 9.16667e-001
Q 1 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 1.00000e+000 2.77556e-017 0.00000e+000 1.00000e+000 2.77556e-017 0.00000e+000 9.16667e-001
*
*

0 1mX1mX1m cube (n=3 e=0.1)
* xo = 0, yo = 0, zo = 0
* view from -x, -y, +z
* This is the plane on y-z plane
*
* back right
Q 1 0.00000e+000 0.00000e+000 0.00000e+000 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 0.00000e+000
Q 1 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 0.00000e+000
Q 1 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 1.00000e+000 0.00000e+000
Q 1 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 8.33333e-002
Q 1 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 8.33333e-002
Q 1 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 1.00000e+000 8.33333e-002
Q 1 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000 1.00000e+000 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 8.33333e-002 9.16667e-001
Q 1 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 9.16667e-001 9.16667e-001
Q 1 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 1.00000e+000 1.00000e+000 0.00000e+000 1.00000e+000 9.16667e-001
*

0 1mX1mX1m cube (n=3 e=0.1)
* xo = 0, yo = 0, zo = 0
* view from -x, -y, +z
* This is the plane on the x-y plane
*
* bottom
Q 1 0.00000e+000 0.00000e+000 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000
Q 1 8.33333e-002 0.00000e+000 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000
Q 1 9.16667e-001 0.00000e+000 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 1.00000e+000 0.00000e+000 0.00000e+000
Q 1 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000
Q 1 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000
Q 1 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000
Q 1 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000 1.00000e+000 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000
Q 1 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000
Q 1 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 1.00000e+000 1.00000e+000 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000
*

Rio
[/quote]

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T O P I C R E V I E W
Rio	Posted - Dec 01 2011 : 23:49:58 Hi all, I really need some help here. I have two square conductors (same shape and put parallel to each other) and I calculate their capacitance matrix and got the following thing: CAPACITANCE MATRIX, picofarads 1 2 1%GROUP1 1 292.2 -93.49 1%GROUP2 2 -93.49 103 I expect the two self-capacitanc to be the same value but they are not. I do not think the code has anything wrong but I attach it here. I really can not understand this why so I ask for help here. Anybody knows what happened? The code is attached: This file is Square_5_0_0.lst Test geometry to show the self/mutual capacitance between 1x1 bus conductors * FastCap2 surface list file for two parallel conductors * Both of the two are consisted with the back_left surface, the back_right surface and the bottom surface * The first conductor * The two side surfaces C back_left.qui 1 0 0 0 + C back_left.qui 1 0 1 0 + C back_left.qui 1 5 0 0 + C back_left.qui 1 5 1 0 + C back_left.qui 1 1 0 0 + C back_left.qui 1 1 1 0 + C back_left.qui 1 6 0 0 + C back_left.qui 1 6 1 0 + C back_left.qui 1 2 0 0 + C back_left.qui 1 2 1 0 + C back_left.qui 1 7 0 0 + C back_left.qui 1 7 1 0 + C back_left.qui 1 3 0 0 + C back_left.qui 1 3 1 0 + C back_left.qui 1 8 0 0 + C back_left.qui 1 8 1 0 + * The bottom abd the top surfaces C bottom.qui 1 0 0 0 + C bottom.qui 1 0 0 1 + C bottom.qui 1 5 0 0 + C bottom.qui 1 5 0 1 + C bottom.qui 1 1 0 0 + C bottom.qui 1 1 0 1 + C bottom.qui 1 6 0 0 + C bottom.qui 1 6 0 1 + C bottom.qui 1 2 0 0 + C bottom.qui 1 2 0 1 + C bottom.qui 1 7 0 0 + C bottom.qui 1 7 0 1 + C bottom.qui 1 3 0 0 + C bottom.qui 1 3 0 1 + C bottom.qui 1 8 0 0 + C bottom.qui 1 8 0 1 + * The front and the back surfaces C back_right.qui 1 0 0 0 + C back_right.qui 1 5 0 0 + C back_right.qui 1 4 0 0 C back_right.qui 1 9 0 0 0 1mX1mX1m cube (n=3 e=0.1) * xo = 0, yo = 0, zo = 0 * view from -x -y +z * This is the square-plane on x-z plane * * back left Q 1 1.00000e+000 0.00000e+000 0.00000e+000 1.00000e+000 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 0.00000e+000 Q 1 9.16667e-001 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 0.00000e+000 Q 1 8.33333e-002 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 8.33333e-002 2.77556e-017 0.00000e+000 8.33333e-002 2.77556e-017 0.00000e+000 0.00000e+000 Q 1 1.00000e+000 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 8.33333e-002 Q 1 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 8.33333e-002 Q 1 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 9.16667e-001 2.77556e-017 0.00000e+000 9.16667e-001 2.77556e-017 0.00000e+000 8.33333e-002 Q 1 1.00000e+000 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 9.16667e-001 Q 1 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 9.16667e-001 Q 1 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 1.00000e+000 2.77556e-017 0.00000e+000 1.00000e+000 2.77556e-017 0.00000e+000 9.16667e-001 * * 0 1mX1mX1m cube (n=3 e=0.1) * xo = 0, yo = 0, zo = 0 * view from -x, -y, +z * This is the plane on y-z plane * * back right Q 1 0.00000e+000 0.00000e+000 0.00000e+000 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 0.00000e+000 Q 1 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 0.00000e+000 Q 1 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 1.00000e+000 0.00000e+000 Q 1 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 8.33333e-002 Q 1 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 8.33333e-002 Q 1 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 1.00000e+000 8.33333e-002 Q 1 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000 1.00000e+000 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 8.33333e-002 9.16667e-001 Q 1 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 9.16667e-001 9.16667e-001 Q 1 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 1.00000e+000 1.00000e+000 0.00000e+000 1.00000e+000 9.16667e-001 * 0 1mX1mX1m cube (n=3 e=0.1) * xo = 0, yo = 0, zo = 0 * view from -x, -y, +z * This is the plane on the x-y plane * * bottom Q 1 0.00000e+000 0.00000e+000 0.00000e+000 0.00000e+000 8.33333e-002 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000 Q 1 8.33333e-002 0.00000e+000 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000 Q 1 9.16667e-001 0.00000e+000 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 1.00000e+000 0.00000e+000 0.00000e+000 Q 1 0.00000e+000 8.33333e-002 0.00000e+000 0.00000e+000 9.16667e-001 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 8.33333e-002 0.00000e+000 Q 1 8.33333e-002 8.33333e-002 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 8.33333e-002 0.00000e+000 Q 1 9.16667e-001 8.33333e-002 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 1.00000e+000 8.33333e-002 0.00000e+000 Q 1 0.00000e+000 9.16667e-001 0.00000e+000 0.00000e+000 1.00000e+000 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 8.33333e-002 9.16667e-001 0.00000e+000 Q 1 8.33333e-002 9.16667e-001 0.00000e+000 8.33333e-002 1.00000e+000 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 9.16667e-001 9.16667e-001 0.00000e+000 Q 1 9.16667e-001 9.16667e-001 0.00000e+000 9.16667e-001 1.00000e+000 0.00000e+000 1.00000e+000 1.00000e+000 0.00000e+000 1.00000e+000 9.16667e-001 0.00000e+000 * Rio
1 L A T E S T R E P L I E S (Newest First)
dave_royle	Posted - Dec 15 2011 : 08:45:33 Rio, Your descretization is way too coarse. You need to create your .qui files with more sections. Use one of the canned programs like cubegen. The more panels you use, the more accurate the model, and the less likely you are to get asymmetries. An example of this concept is shown in figure 4, page 13 of the User Guide (coarse vs. fine descretization of sphere). Dave

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