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Capacitance for MEMS cantilever

Posted Dec 10, 2010, 3:49 p.m. EST Low-Frequency Electromagnetics, MEMS & Nanotechnology, MEMS & Piezoelectric Devices Version 3.5a 4 Replies

Amir
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I am trying to recreate the Mems cantilever model for calculating the cantilever capacitance but when i am trying to plot the function
with(V_in,Q)-with(V_in-1,Q)
the comsol errors
Please help me with this operator (with)
Thanx
4 Replies Last Post Dec 11, 2010, 1:31 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 11, 2010, 5:10 a.m. EST
Hi

Have you checked in the Model Library, there are at least one example there, the formulas depend a little on the model/pysics type but I'm puzzled and do not understand your formula there

--
Good luck
Ivar
Hi Have you checked in the Model Library, there are at least one example there, the formulas depend a little on the model/pysics type but I'm puzzled and do not understand your formula there -- Good luck Ivar
Amir
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Posted: 1 decade ago Dec 11, 2010, 8:44 a.m. EST
Thank you
Yes I've checked it and I was trying to repeat all the instructions in the documentation [documentation for simulation of a mems cantilever] but in postprocessing part where the capacitance is calculated I cannot get the plot described in the documentation instead comsol says that it cannot understand the "with operator"
the documentation is attached.
Please help me with this.
Also i cannot find anything about that "with" operator too, please give me a reference for finding information about it or ...
Thank you Yes I've checked it and I was trying to repeat all the instructions in the documentation [documentation for simulation of a mems cantilever] but in postprocessing part where the capacitance is calculated I cannot get the plot described in the documentation instead comsol says that it cannot understand the "with operator" the documentation is attached. Please help me with this. Also i cannot find anything about that "with" operator too, please give me a reference for finding information about it or ...

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 11, 2010, 11:38 a.m. EST
Hi

normally the with() ad at() operators are used to catch a moment in a transient analysis (at() the desired interpolated time moment t) and the with() at the frequency (frequency sweep) or particular mode (eigenfrequency analysis)
These operators are described in the doc, do an indexed search on the doc to find them ;)

There are also examples of apacitive extraction depending on the model you build.

--
Good luck
Ivar
Hi normally the with() ad at() operators are used to catch a moment in a transient analysis (at() the desired interpolated time moment t) and the with() at the frequency (frequency sweep) or particular mode (eigenfrequency analysis) These operators are described in the doc, do an indexed search on the doc to find them ;) There are also examples of apacitive extraction depending on the model you build. -- Good luck Ivar
Amir
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Posted: 1 decade ago Dec 11, 2010, 1:31 p.m. EST
Hi and thank you

Yes I see..
but why when I want to calculate the value it gives me :
Error 8032
with(V_in,Q)-with(V_in-1,Q) is not a valid global expression
i also attach the picture.
Thank you very much for your help
Hi and thank you Yes I see.. but why when I want to calculate the value it gives me : Error 8032 with(V_in,Q)-with(V_in-1,Q) is not a valid global expression i also attach the picture. Thank you very much for your help

Attachments:

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