Which Of The Following Changes Will Increase The Capacitance Of A Parallel-plate Capacitor?

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capacitance of a parallel plate capacitor

Posted Nov 29, 2009, 10:30 p.m. UTC Version 4.0, Version 4.one, Version 4.2

Svetlana Avramov-Zamurovic

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These are the steps for my capacitor simulation
1. gear up two solid blocks (dimensions (25x1x20) ) 1 distance away from each other.
2. set a solid box (65x43x60) to environment the plates of the capacitor.
3. subtracted plates from the surrounding box.
4. set up the plates to exist copper and surrounding box to be air.
v. gear up one plate to exist port 1 ( defined as input) ; set the other plate to be port 2; used energy method
vi. set the surrounding box to be basis
vii.meshed and got the solution
I calculated theoretically what the capacitance for a parallel plate capacitor should be 0.004425 pF
My COMSOL result is xxx% off ( 0.005736977 pF). I do not believe this is realistic.
Tin somebody help me find an error in my process?
Svetlana

Luca Ferrario

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Posted: i decade ago November 30, 2009, 10:04 a.1000. UTC

Hi Svetlana
I remember that you should try to utilise forced voltage method, you should set 1 plate like input(check the voice Use port as input) with whatever kind of voltage and the second plate with another port number without input.
I used this method to validate sperimental values and i institute the same solutions.

Bye
Luca

Hello Svetlana I think that you should try to utilise forced voltage method, you lot should fix ane plate similar input(check the vocalization Employ port as input) with whatsoever kind of voltage and the second plate with some other port number without input. I used this method to validate sperimental values and i found the same solutions. Bye Luca

Maarten Cauwe

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Posted: 1 decade ago Dec 1, 2009, one:33 p.m. UTC

But gear up the second plate as footing in stead of port ii and leave the box floating.

This kind of parallel-plate capacitor can be done much easier in 2D.

Maarten.

Merely set the 2nd plate as basis in stead of port two and leave the box floating. This kind of parallel-plate capacitor tin can exist done much easier in 2D. Maarten.

Svetlana Avramov-Zamurovic

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Posted: 1 decade ago Dec 2, 2009, 12:25 a.m. UTC

Thanks Luca
I did it. The differences between the theory and simualtion are to big
Svetlana

Thanks Luca I did it. The differences betwixt the theory and simualtion are to large Svetlana

Svetlana Avramov-Zamurovic

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Posted: ane decade ago Dec 2, 2009, 12:29 a.m. UTC

Thank you Maarten
but I need 3d model since I plan to design a capacitive sensor to measure a distance from a platform. I too need grounded space since the sensor will be enclosed. This simple problem is only a common sense cheque.
Svetlana

Thanks Maarten only I need 3d model since I plan to blueprint a capacitive sensor to measure a distance from a platform. I also need grounded space since the sensor will be enclosed. This simple problem is just a common sense check. Svetlana

Sunil Patil

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Posted: i decade ago Feb fifteen, 2011, 6:48 a.m. UTC

Give thanks yous Maarten
but I need 3d model since I plan to pattern a capacitive sensor to measure a distance from a platform. I also demand grounded space since the sensor will be enclosed. This simple trouble is just a mutual sense check.
Svetlana

Tin can you please explain how to compute capacitance in to a higher place mentioned problem?
I can go value of C11_emes from sub domain integration in F-thousand^3 for subdomain one and aforementioned value for subdomain 2. If i compute same for subdomain 1 and 2 information technology simply adds up. Is the parallel plate capacitor is C11 or C12?

pls explicate.

[QUOTE] Thank you Maarten only I need 3d model since I program to design a capacitive sensor to measure a distance from a platform. I besides need grounded space since the sensor will be enclosed. This elementary problem is merely a common sense check. Svetlana [/QUOTE] Can you please explain how to compute capacitance in higher up mentioned trouble? I tin can get value of C11_emes from sub domain integration in F-m^3 for subdomain 1 and same value for subdomain 2. If i compute aforementioned for subdomain 1 and 2 information technology simply adds upwards. Is the parallel plate capacitor is C11 or C12? pls explain.

Ivar Kjelberg "Retired" but still function time CSEM SA (CH)

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Posted: ane decade ago Feb 15, 2011, 7:31 a.m. UTC

have yous checked the capacitor models in the model exchange ?

--
Proficient luck
Ivar

Hi have you checked the capacitor models in the model exchange ? -- Good luck Ivar

Sunil Patil

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Posted: i decade ago Feb xv, 2011, nine:44 a.k. UTC

Hi
have y'all checked the capacitor models in the model exchange ?

--
Proficient luck
Ivar

Thank you Ivar,
I take checked, world wide web.comsol.eu/support/knowledgebase/951/.
Even that has C31 -negative.
I am repeating my problem,

I am calculating capacitance between the 2 metallic plates (1m Ten 1m X 1m) with surrounding box grounded. One of the plate boundaries are set as port 1 with forced voltage input=x Five and other equally port two. In one case solved, I go to Postprocessing>Point Evaluation to decide C11 and C12. I get,
Value: 6.476987e-11 [F], Expression: C11_emes, Betoken: 17
Value: -1.775192e-xi [F], Expression: C21_emes, Indicate: 17.

Could you please tell me what might exist the problem?

Thanks very much.
sunil

[QUOTE] Hello take you checked the capacitor models in the model exchange ? -- Good luck Ivar [/QUOTE] Thank y'all Ivar, I have checked, http://www.comsol.eu/support/knowledgebase/951/. Fifty-fifty that has C31 -negative. I am repeating my problem, I am calculating capacitance betwixt the two metallic plates (1m 10 1m Ten 1m) with surrounding box grounded. 1 of the plate boundaries are prepare as port 1 with forced voltage input=10 V and other as port ii. One time solved, I get to Postprocessing>Point Evaluation to make up one's mind C11 and C12. I go, Value: half-dozen.476987e-xi [F], Expression: C11_emes, Betoken: 17 Value: -ane.775192e-eleven [F], Expression: C21_emes, Point: 17. Could you please tell me what might be the problem? Thank you very much. sunil

Ivar Kjelberg "Retired" simply nonetheless part fourth dimension CSEM SA (CH)

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Posted: 1 decade ago Feb xv, 2011, 2:44 p.m. UTC

How-do-you-do

is'nt the port capacitance measurement washed between GND and the port ?

I would effort GND one plate and utilise port1 (but) on the other plate

--
Skilful luck
Ivar

Hi is'nt the port capacitance measurement washed between GND and the port ? I would try GND i plate and use port1 (but) on the other plate -- Good luck Ivar

Lothar Schultheis

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Posted: 1 decade ago Feb 15, 2011, 4:16 p.chiliad. UTC

Hullo
there is an event of conventions within capacitance matrix note used in FEM and in electronics. You should google "non-negative off diagonal capacitive matrix elements"

I copied this from a forum in 2001
------
" The brusk explanation is that in the SPICE capacitance matrix, all
elements are e'er positive. The diagonal elements are the
capacitance to ground and the off diagonals represent the coupling
betwixt conductors.

The other matrix is the Maxwell capacitance matrix. The definition of
the Maxwell C matrix elements is unlike from the SPICE C matrix. In
the Maxwell C matrix, all off diagonal elements are always negative
and the diagonal elements represent the "loaded capacitance" or "total
capacitance". The off diagonal elements of each matrix are numerically
equal. If you lot take one row of the Maxwell C matrix and add together upwards all the
elements, it volition be equal to the diagonal element in the
corresponding row of the SPICE C matrix.

The quick manner to tell if you've got a C matrix from a field solver
consequence is to expect at the off diagonal elements. If they are negative,
information technology came from a field solver. I have tried in vane, to go field solver
companies to label their capacitance matrices as Maxwell Capacitance
matrices, to help avoid the confusion and emphasize the fact that
at that place really are two different matrices, each with a slightly
different definition. So far, only Ansoft has done this."

Hope this helps

Lothar

------

Hi there is an issue of conventions within capacitance matrix notation used in FEM and in electronics. You should google "non-negative off diagonal capacitive matrix elements" I copied this from a forum in 2001 ------ " The curt explanation is that in the SPICE capacitance matrix, all elements are always positive. The diagonal elements are the capacitance to ground and the off diagonals represent the coupling between conductors. The other matrix is the Maxwell capacitance matrix. The definition of the Maxwell C matrix elements is different from the SPICE C matrix. In the Maxwell C matrix, all off diagonal elements are always negative and the diagonal elements stand for the "loaded capacitance" or "total capacitance". The off diagonal elements of each matrix are numerically equal. If yous take i row of the Maxwell C matrix and add together up all the elements, it will exist equal to the diagonal chemical element in the corresponding row of the SPICE C matrix. The quick manner to tell if you've got a C matrix from a field solver result is to look at the off diagonal elements. If they are negative, it came from a field solver. I have tried in vane, to get field solver companies to label their capacitance matrices every bit Maxwell Capacitance matrices, to help avoid the confusion and emphasize the fact that at that place actually are two unlike matrices, each with a slightly different definition. So far, only Ansoft has done this." Hope this helps Lothar ------

Ivar Kjelberg "Retired" merely nevertheless part fourth dimension CSEM SA (CH)

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Posted: ane decade ago Feb 16, 2011, six:20 a.chiliad. UTC

interesting, is it worth to inquire support to analyze this in the COMSOL physician too ?

--
Skilful luck
Ivar

Howdy interesting, is it worth to inquire back up to analyze this in the COMSOL doc too ? -- Good luck Ivar

Sunil Patil

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Posted: i decade agone Feb 16, 2011, 10:40 a.m. UTC

Thank y'all for your response. Well I am not the cadre Mathematician or physicist. For time being, may I know which numbers here brand sense for parallel plate capacitor? I hateful C11 or C12? if not then how to become it?

Thanks for your response. Well I am not the core Mathematician or physicist. For fourth dimension being, may I know which numbers hither brand sense for parallel plate capacitor? I mean C11 or C12? if not then how to get information technology?

Ivar Kjelberg "Retired" just nevertheless role time CSEM SA (CH)

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Posted: 1 decade ago Feb xvi, 2011, eleven:18 a.yard. UTC

Howdy

knowing that

C[F] = epsilon[F/m]*epsilonr[ane]*A[m^ii]/d[grand]

and if I sympathize yous well you have an plate area of A=ane[m^2] and a plate altitude of d=1[m], and knowing that epsilon=8.85E-12[F/thou] and epsilonr=ane for air you should select the one getting closest. I assume the C11 is the one

But again, check advisedly the COMSOL md if the port value is not evaluated between GND and the port entry (and not between 2 ports)

Some "fringe field" furnishings could give some differences, a few % I would await

--
Practiced luck
Ivar

Howdy knowing that C[F] = epsilon[F/k]*epsilonr[1]*A[m^2]/d[1000] and if I understand you well you have an plate area of A=1[m^2] and a plate distance of d=1[one thousand], and knowing that epsilon=8.85E-12[F/m] and epsilonr=1 for air y'all should select the i getting closest. I assume the C11 is the one But once more, check advisedly the COMSOL doc if the port value is not evaluated betwixt GND and the port entry (and not between ii ports) Some "fringe field" effects could give some differences, a few % I would expect -- Good luck Ivar

Sunil Patil

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Posted: 1 decade agone Feb 16, 2011, 11:24 a.m. UTC

Give thanks you Ivar,
I am getting C11 with i plate along with outer box grounded and some other as port one.
Value: 6.476987e-11 [F], Expression: C11_emes, Indicate: 17

whereas, if outer box kept floating, and then C11 comes,

Value: iv.878925e-11 [F], Expression: C11_emes, Point: 17

Sunil

Give thanks yous Ivar, I am getting C11 with one plate along with outer box grounded and another as port 1. Value: six.476987e-11 [F], Expression: C11_emes, Point: 17 whereas, if outer box kept floating, then C11 comes, Value: 4.878925e-xi [F], Expression: C11_emes, Bespeak: 17 Sunil

Ivar Kjelberg "Retired" but however part fourth dimension CSEM SA (CH)

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Posted: i decade ago February 16, 2011, 3:01 p.g. UTC

In 4.1 if I brand a single centered 1m^three box, surrounded by a 10m radial sphere, all epsilonr=i, gnd on 1 side of the box, of 1m^2 area, a port 1 (1V) on the other. I get es.C11 four.45E-11[F] with a normal mesh, and stationary solver

However, I have also tried to make the electrodes rather thick (not simply an interior boundary, then I become easily xxx% fringe effects, and then the original thread (autonomously that the units in um where not mentioned) results differences are for me realistic.

If I ground my sphere external surface (instad of "0" accuse) I get vi.56E11 I'thou not astonished the interacting area is higher even if the altitude is larger

By increasing the mesh density to "finer" I go to 5.6E-11F for external surface area grounded, and it's hardly changing with the external area radius being changed between 2.five to 10m. While with the external shell floating and "finer" mesh I become three.76E-11[F],

Patently the mesh density is too poor at "normal" values. Furthermore, I take a square electrode, with corners = singularities in ACDC.

==========

If I endeavor a cylinder of radius sqrt(one/pi) and length 1m hence the same area of one[thou^2] and inter-electrode altitude of ane[yard] I become only 3e-11F with the 10m spherical vanquish floating, and 4.6E-11F with the shell at GND for finer mesh Also for the normal mesh (to within ii%)

adding an external infinite beat out does neither not change any calculated values

CONCLUSIONS for me:
- Ever check the mesh dependence (nada new)
- Always consider "smoothing" sharp corner (singularities) in ACDC (neither not new)
- some 30-50% changes on capacitive values are easily obtained due to fringe effects

In fact I see many similarities with the Maxwell stress tensor calculations for solving forces in ACDC

--
Good luck
Ivar

Hello In 4.i if I brand a single centered 1m^3 box, surrounded past a 10m radial sphere, all epsilonr=1, gnd on one side of the box, of 1m^2 surface area, a port ane (1V) on the other. I become es.C11 four.45E-xi[F] with a normal mesh, and stationary solver However, I have too tried to brand the electrodes rather thick (not just an interior boundary, then I get hands thirty% fringe effects, so the original thread (apart that the units in um where non mentioned) results differences are for me realistic. If I ground my sphere external surface (instad of "0" charge) I get half-dozen.56E11 I'1000 not astonished the interacting expanse is higher even if the distance is larger By increasing the mesh density to "effectively" I get to five.6E-11F for external surface area grounded, and information technology's hardly irresolute with the external area radius being inverse between 2.5 to 10m. While with the external shell floating and "finer" mesh I go iii.76E-11[F], Obviously the mesh density is too poor at "normal" values. Furthermore, I have a square electrode, with corners = singularities in ACDC. ========== If I endeavor a cylinder of radius sqrt(1/pi) and length 1m hence the aforementioned area of 1[yard^2] and inter-electrode altitude of 1[m] I go only 3e-11F with the 10m spherical trounce floating, and iv.6E-11F with the shell at GND for finer mesh AS well for the normal mesh (to within 2%) adding an external infinite shell does neither not alter whatsoever calculated values CONCLUSIONS for me: - E'er check the mesh dependence (zero new) - Ever consider "smoothing" sharp corner (singularities) in ACDC (neither not new) - some thirty-50% changes on capacitive values are easily obtained due to fringe effects In fact I meet many similarities with the Maxwell stress tensor calculations for solving forces in ACDC -- Good luck Ivar

Ivar Kjelberg "Retired" but however role time CSEM SA (CH)

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Posted: 1 decade agone Feb 16, 2011, 3:02 p.m. UTC

Sorry, I forgot to attach the other file, and once posted one seem to not to exist able to "reattach a file ?
--
Take fun COMSOLING
Ivar

Sorry, I forgot to attach the other file, and once posted ane seem to not to be able to "reattach a file ? -- Have fun COMSOLING Ivar

Lothar Schultheis

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Posted: ane decade ago Feb 16, 2011, 6:08 p.chiliad. UTC

I think if the capacitor consists of port 1 and 2 with surrounding grounded then:
C11 measures (simply is non equal to!) capacitance of port 1 to gnd
C22 measures (but is not equal to!) capacitance of port ii to gnd
-C12 (=-C21) is the capacitance of port 1 to port two

Good luck

Lothar

Hi I think if the capacitor consists of port ane and 2 with surrounding grounded so: C11 measures (but is not equal to!) capacitance of port one to gnd C22 measures (but is non equal to!) capacitance of port ii to gnd -C12 (=-C21) is the capacitance of port 1 to port 2 Skilful luck Lothar

Ivar Kjelberg "Retired" but still part time CSEM SA (CH)

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Posted: 1 decade ago Feb 17, 2011, x:57 a.m. UTC

well in V4 there is only C11 or C22 no cross values, and anyhow if I create two ports I get the double of the capacity than for 1 port, sounds logic no ?

--
Expert luck
Ivar

Hi well in V4 there is only C11 or C22 no cross values, and anyhow if I create two ports I get the double of the capacity than for 1 port, sounds logic no ? -- Practiced luck Ivar

ABDUL

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Posted: 1 decade ago Jun viii, 2011, v:26 p.g. UTC

how-do-you-do
please i want to draw the geometry of parallel plate capacitor.i am new user of comsol please guide me

hello delight i want to draw the geometry of parallel plate capacitor.i am new user of comsol please guide me

ABDUL

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Posted: i decade ago Jun eleven, 2011, seven:01 a.m. UTC

hi
delight i desire to draw the geometry of parallel plate capacitor.i am new user of comsol please guide me

delight help me

[QUOTE] howdy please i want to draw the geometry of parallel plate capacitor.i am new user of comsol delight guide me [/QUOTE] delight aid me

Neethu Kori

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Posted: 10 years ago February sixteen, 2012, 5:10 a.m. UTC

Howdy.

Am the new user of COMSOL pls help me out in designing the 3d Model of Parallel plate capacitor.

HI. Am the new user of COMSOL pls help me out in designing the 3d Model of Parallel plate capacitor.

Ivar Kjelberg "Retired" just still part time CSEM SA (CH)

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Posted: x years ago Feb 16, 2012, 7:24 a.thousand. UTC

check the model library and the principal web site videos / demos /tutorials that should give you a practiced beginning ;)

--
Good luck
Ivar

Hello bank check the model library and the main web site videos / demos /tutorials that should requite you a good start ;) -- Adept luck Ivar

Hesham Omran

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Posted: 9 years ago Aug 15, 2012, xi:26 a.yard. UTC

Hullo

I am using 4.ii
I take ii electrodes on superlative of ground plane
How to measure the cantankerous cap betwixt the electrodes, and the cap of each to basis?

Howdy I am using four.2 I accept ii electrodes on height of basis airplane How to measure the cantankerous cap between the electrodes, and the cap of each to footing?

Manuel Aeschbacher

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Posted: nine years agone Oct 18, 2012, 10:14 a.m. UTC

If anyone is interested in that: I have a parallel plate capacitor connected with two terminals one to 10V the other to 0V. Further I have grounded Walls. I this example:
(-)C12 = Capacitance between Port i and Port 2
C22 = Capacitance between Port i and Port 2 but the Ground is treaten every bit floating, and then if you insert a grounded plate between both plates the capacitance will increment.
Thats not what is more often than not wanted. The capacitance should just be measured between Port 1 and 2.

If anyone is interested in that: I have a parallel plate capacitor connected with two terminals one to 10V the other to 0V. Further I have grounded Walls. I this case: (-)C12 = Capacitance between Port 1 and Port ii C22 = Capacitance between Port 1 and Port two only the Ground is treaten as floating, so if you lot insert a grounded plate between both plates the capacitance will increase. Thats not what is by and large wanted. The capacitance should simply be measured between Port 1 and 2.

Ivar Kjelberg "Retired" but all the same part time CSEM SA (CH)

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Posted: ix years agone October 18, 2012, 1:22 p.m. UTC

Hello

I believe that the capacitance is defined between GND and i port/final, non between two terminals. And in 4.3a the capacitance variable does not show up if you have more than than ane terminal. Check your doc

--
Skillful luck
Ivar

Hi I believe that the capacitance is defined between GND and 1 port/final, non betwixt two terminals. And in 4.3a the capacitance variable does not evidence up if you have more than i concluding. Check your md -- Good luck Ivar

Abid Iqbal

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Posted: 9 years agone Nov half-dozen, 2012, 4:19 a.m. UTC

Dear Ivar
I want to utilize the ac voltage on two parallel plate capacitor, how tin i utilise on it? I have tried the electrostatic module with moving ridge function and applied it to the capacitor plate and with negative side on the other plate. i dont know whether information technology is correct or not. the second matter is that i want to modify the electrical field pointer with its magnitude but information technology remain same.
Please assistance me in this regards.
Abid

Dear Ivar I desire to utilize the ac voltage on 2 parallel plate capacitor, how tin can i use on it? I have tried the electrostatic module with wave function and applied information technology to the capacitor plate and with negative side on the other plate. i dont know whether it is correct or not. the second thing is that i want to change the electric field arrow with its magnitude merely it remain same. Delight help me in this regards. Abid

Ivar Kjelberg "Retired" but still role time CSEM SA (CH)

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Posted: 9 years agone Nov 6, 2012, v:44 a.m. UTC

Hullo

the easiest is t employ GND on one and set an amplitude on a concluding on the other plate, and so solve with a frequency domain solver and add together the Air-conditioning frequency(or full frequency range) in the solver node

--
Good luck
Ivar

Hi the easiest is t utilize GND on i and set an amplitude on a last on the other plate, then solve with a frequency domain solver and add the AC frequency(or full frequency range) in the solver node -- Good luck Ivar

Jeffrey Fong

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Posted: 9 years ago Mar 24, 2013, half dozen:35 a.m. UTC

Howdy
I believe that the capacitance is divers between GND and one port/terminal, not between ii terminals. And in 4.3a the capacitance variable does not show up if yous take more one terminal. Check your md

--
Good luck
Ivar

What if you wanted to model alternate plates with negative and positive voltages across from 2 different sets of alternate grounds?

ie.

GND1 GND2 GND1 GND2
--------- --------- --------- ---------

--------- --------- --------- ---------
+100V -100V +100V -100V

[QUOTE] How-do-you-do I believe that the capacitance is defined between GND and i port/concluding, not between two terminals. And in iv.3a the capacitance variable does not evidence upwards if you have more ane terminal. Check your doc -- Expert luck Ivar [/QUOTE] What if you wanted to model alternating plates with negative and positive voltages across from 2 different sets of alternating grounds? ie. GND1 GND2 GND1 GND2 --------- --------- --------- --------- --------- --------- --------- --------- +100V -100V +100V -100V

Ivar Kjelberg "Retired" but yet part time CSEM SA (CH)

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Posted: ix years ago Mar 24, 2013, vi:47 p.m. UTC

here you have capcitive couplings betwixt the different "gnd" and the different electrodes. Equally the chapters is indepenent of absolute voltage you can model 2 by ii, or use the full equations as C is linking dI/dt and U and when you lot solve y'all get both U and I in EC

--
Adept luck
Ivar

Hullo here yous have capcitive couplings between the unlike "gnd" and the different electrodes. Equally the chapters is indepenent of absolute voltage you can model 2 by 2, or utilize the total equations as C is linking dI/dt and U and when y'all solve you get both U and I in EC -- Practiced luck Ivar

Primož Cuznar

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Posted: viii years agone Mar vii, 2014, 6:xix p.m. UTC

How-do-you-do!
I am analysing capacitance over few layers and I wonder why those spikes appear in attached file? Is this some kind of numerical/computing problem? I think it should be flatline ... problem could be when voltage passes 0V betoken, yes?

applied voltage: 0.5*sin(2*pi*400*t [one/s])
fourth dimension: range(10^(-6), 2.v*x^(-4), 0.125)

Could anyone answer? Thank you

Hi! I am analysing capacitance over few layers and I wonder why those spikes appear in attached file? Is this some kind of numerical/computing problem? I recollect it should be flatline ... trouble could be when voltage passes 0V point, yes? applied voltage: 0.v*sin(2*pi*400*t [1/s]) time: range(10^(-half-dozen), two.five*10^(-4), 0.125) Could anyone answer? Thank you