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Getting capacitance from Impedance/admittance
Posted 16 mar 2011, 10:00 GMT-4 Low-Frequency Electromagnetics Version 5.2 6 Replies
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I am modeling an impedance/capacitance sensor. I have a static model and the results are very promising, now Im trying to expand my model and model a frequency domain study: the voltage applied is a frequency parameter sweep between 1 and 8 MHz. Using the Electric currents interface I can get admittance of the system as a variable but I would also like to know the capacitance of the system.
Since the device is basicaly a microstrip capacitor then I can get the Capacitnace by dividing theimaginary part of admittance by angular frequency.
C = jY/w.
But is there a way to do it automaticaly? There is an example in the library - capacitance in a microstrip(Model ID 966), its exactly what Im trying to do but it is made for 3.5 and when i open it in 4 or 4.1 it seems to work as it should: there are electro statics and magnetic fields physics interfaces and the study is stationary... Solving it brings up an error. Reading the .pdf file for it I found that you can do that by plotting "imag(Y11_emqap)/omega_emqap". However the the variable with imaginary part of admittance doesnt seem to be present in the electric currents interface...
Any help apreciated.
Cheers.
- Fjodor
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I am wondering how did you do the electrostatics when you want to sweep the frequency for modeling the capacitance. And how did you interface the electric currents model?
Thanks,
Yemin
Ugh... I think I solved my problem: there is nothing preventing me from making a model with 2 interfaces: currentss for admittance and electrostatics for Capacitance.
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I think he did two studies:
a stationary one with the electrostatics interface
and
a frequency sweep with the electric currents interface
In the first case, the capacitance is accessible directly.
In the second case, the capacitance can be computed using the admittance COMSOL gives you.
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Ugh... I think I solved my problem: there is nothing preventing me from making a model with 2 interfaces: currentss for admittance and electrostatics for Capacitance.
this helped. thanks
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Hi,
I think he did two studies:
a stationary one with the electrostatics interface
and
a frequency sweep with the electric currents interface
In the first case, the capacitance is accessible directly.
In the second case, the capacitance can be computed using the admittance COMSOL gives you.
Is it ok to do the simulation with both the studies EC and ES in the same model.
And choosing the es simulation for capacitance and then choosing ec and running simulation again to see admittance ?
Is there any interaction between es and ec physics.
should this be run as two separate model files in that case ?
Please login with a confirmed email address before reporting spam
Hello,
I am wondering how did you do the electrostatics when you want to sweep the frequency for modeling the capacitance. And how did you interface the electric currents model?
Thanks,
Yemin
Ugh... I think I solved my problem: there is nothing preventing me from making a model with 2 interfaces: currentss for admittance and electrostatics for Capacitance.
electrostatics works with frequency domain study (essentially sweep of frequency)
this gives frequency vs Capacitance values.
This is same as that given in the example
www.comsol.com/model/computing-capacitance-12689
Thanks