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                                                Posted:
                            
                                2 decades ago                            
                            
                                2009年10月16日 GMT+8 18:42                            
                        
                        
                                                    Sorry I had some troubles with pc...so I continue to explain:
Capacitor: Port number 1
                Input property:forced voltage
                I also use it as input , 1V
Mass         Port number 2
                Input prop, forced voltage
I create a third block that simulate the environment(boundaries condition for environment zero charge/symmetry) and at the end I launch the analysis.
In global variables I find ther capacitance between the 2 blocks C12_emes and i find the results that is around the value of experimental evaluation. The problem is that if I change the dimensions of the environment block with the same conditions I find different values of capacitance.
So I would ask if i make some errors in the simulation.
Thank you in advance 
Luca                                                
                                                
                            Sorry I had some troubles with pc...so I continue to explain:
Capacitor: Port number 1
                Input property:forced voltage
                I also use it as input , 1V
Mass         Port number 2
                Input prop, forced voltage
I create a third block that simulate the environment(boundaries condition for environment zero charge/symmetry) and at the end I launch the analysis.
In global variables I find ther capacitance between the 2 blocks C12_emes and i find the results that is around the value of experimental evaluation. The problem is that if I change the dimensions of the environment block with the same conditions I find different values of capacitance.
So I would ask if i make some errors in the simulation.
Thank you in advance 
Luca                        
                                                
                                                                                                            
                                             
                                            
                                                
    
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                                                Posted:
                            
                                2 decades ago                            
                            
                                2009年10月17日 GMT+8 19:13                            
                        
                        
                                                    Does the "environment" block encompass your two other blocks (your blocks are within the environment block?)
Remember when dealing with capacitances you get fringe fields and depending on your seperation between the capcitor block and the mass block the fringe fields may be interacting with the boundaries of the environment block, therefore as you change the enviroment block dimensions your capacitance value changes.
Make you environment block as large as possible, certainly the distance of one of your enviro block walls to either the cap or mass block should be at least twice the seperation distance from between cap block and mass block.
Hope this helps?
Regards,
Tom                                                
                                                
                            Does the "environment" block encompass your two other blocks (your blocks are within the environment block?)
Remember when dealing with capacitances you get fringe fields and depending on your seperation between the capcitor block and the mass block the fringe fields may be interacting with the boundaries of the environment block, therefore as you change the enviroment block dimensions your capacitance value changes.
Make you environment block as large as possible, certainly the distance of one of your enviro block walls to either the cap or mass block should be at least twice the seperation distance from between cap block and mass block.
Hope this helps?
Regards,
Tom                        
                                                
                                                                                                            
                                             
                        
                        
                            
                                                                                        
                                Ivar KJELBERG
                                                                                                                                                    COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
                                                         
                            
                         
                                                
    
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                                                Posted:
                            
                                2 decades ago                            
                            
                                2009年10月18日 GMT+8 05:11                            
                        
                        
                                                    Hi
have you checked out the latest models in the "ModelExchange" ? I believe you can find some useful hints there ! Konrad Walus of University of British Columbia has just deposited quite some nice models there
Good luck
Ivar                                                
                                                
                            Hi
have you checked out the latest models in the "ModelExchange" ? I believe you can find some useful hints there ! Konrad Walus of University of British Columbia has just deposited quite some nice models there
Good luck
Ivar