Discussion Forum

Hi

check the port/terminal boundary condition and change the terminal type from Charge "Q" to Voltage "V"

But this assumes you are using EC / ES / ECS physics for your MEMS

in V4 the physics are separate and not merge by applications as in V3.5a

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Good luck
Ivar

thax u sir for ur reply

wht u told sir i already tried but it is giving stationary solver error

the step that i followed

electrostatic>terminal>i selected the boundary and in terminal type i gvn voltage

after that v0 = ? (here )

once i given v0= vac*sin(2*pi*f*t)
again i tried it v0=2mV but sir it is giving following error
............................................................................................................................................
Segregated group 1
Failed to evaluate variable.
- Variable: mat.epsilonr22
- Geometry: 1
- Domain: 1
Failed to evaluate variable.
- Variable: mod1.es2.epsilonryy
- Defined as: mat.epsilonr22
Failed to evaluate variable.
- Variable: mod1.es2.Dy
- Defined as: (mod1.es2.Ey*(mod1.es2.epsilonryy*epsilon0_const))
Failed to evaluate expression.
- Expression: d((-mod1.es2.Dx*test(mod1.Vx)-mod1.es2.Dy*test(mod1.Vy)-mod1.es2.Dz*test(mod1.Vz))*(dvol_spatial),{test@7})

........................................................................................................

Hi

if you use a stationary solver then "t" is not defined, or rather set to t=0 by default.

If you want to do a frequency response you define the amplitude and use a frequency solver that implies the sin(2*pi*freq*t) by default. Check the doc for the different solver types

--
Good luck
Ivar

again thax for replying me sir

sir i want to do frequency response for that i used the freq solver

but i need to apply ac voltage of 2mV and dc voltage of 20V

so how can i apply this

Hi

not 100% sure it works:
but in principle, I would try a stationary solver with the DC value, store the solution, and use that as linearisation point for the frequency sweep.
But, what I'm stating here is a transposition of the eigenfrequency response methodology (do one that first to check where the modes should be and then compare with the frequency sweep peaks, if they are the same it should be OK, they should be also different from the pure eigenmode analysis without any prestress)

In anycase you must be sure that the DC voltage does apply some stress or something that is used further in the frequency mode analysis, otherwise you can forget the DC level ;)

i.e if you apply a body load (i.e.gravity) to a cantilever beam and do an eigenfreuqency analysis, by defauklt the external forces are ignored and you the the "unstressed modes", independent if you apply a load or not. YOu must 1) prestress and store a DC solution, then thell the eigensolver to use the stored solution as starting point to get any potential change in frequency due to stress stiffeneing (or weakening)

--
Good luck
Ivar

Sir,

I am also facing the exact same situation . I hope you have found out a solution by now. Please reply me a solution.

respected sir

i m creating a mems based disk resonator on comsol4.1
structure is drawn and i need to apply a AC VOLTAGE OF 2mV TO ONE OF THE ELECTRODE IN MY STRUCTURE.

can anyone help me how to apply ac voltage in comsol4.1 if possible please give the steps

i will be grateful to u sir
thax

Hi guys

Define a variable that is valid on the electrode. But in my solution you need to use time-dependent model. For example like this:

Parameters:

Edc: 200[mV]
A: 2[mV]
f: 100[Hz]
w: 2*pi*f

Definitions, variables, Geometry entity level: Boundary
E: Edc+A*sin(w*t)

Hope this is an answer to your problem.

Hi guys

Define a variable that is valid on the electrode. But in my solution you need to use time-dependent model. For example like this:

Parameters:

Edc: 200[mV]
A: 2[mV]
f: 100[Hz]
w: 2*pi*f

Definitions, variables, Geometry entity level: Boundary
E: Edc+A*sin(w*t)

Hope this is an answer to your problem.

Hi Lasse,
I saw your replay in the Comsol forum and ask help from you. I want to add DC voltage and AC voltage on one capacitor plate, in frequency domain and I will analysis the frequency response. How should I add the Vac?how to solve the 't' problem? Please help me ! Thanks in advance!

respected sir

i m creating a mems based disk resonator on comsol4.1
structure is drawn and i need to apply a AC VOLTAGE OF 2mV TO ONE OF THE ELECTRODE IN MY STRUCTURE.

can anyone help me how to apply ac voltage in comsol4.1 if possible please give the steps

i will be grateful to u sir
thax

Hi Vikram,
I saw your replay in the Comsol forum and ask help from you. I want to add DC voltage and AC voltage on one capacitor plate, in frequency domain and I will analysis the frequency response. How should I add the Vac?how to solve the 't' problem? Please help me ! Thanks in advance!

Hello,

I am following the tutorial of Electrowetting Lens with a different geometric shape. I'm not sure how to apply voltage to this example. Do I need to add EC / ES / ECS physics in order to apply voltage?

where do I get this information. Like frequency domain takes 2pi*f*t by default.

what should i refer to know more about this in comsol?