How to create frequency dependent resistor with laplace block in multisim ?

[neomind]

Hi at all

I'm trying to use arbitrary laplace function to simulate capacitor Zc=1/C*s, or Resistor dependent of frequency

Any example ?

tks

best regards

[Tien_P]

Hi,

There is a transfer function block component, it is located in the "Source" groups under the "Control Function Block" family.  When you place this part on the work area, double click in and you can enter your transfer function expression.

[neomind]

tks for answer, but i don't obtain the results

When i simulate the desing in atachement, i obtain this : green laplace block / red : real response

What is wrong in my desing anexed ?

[Tien_P]

Hi Neomind,

At node Vc, the transfer function the circuit is: R3C1s/((R1+R3)C1s+1)

Enter the above expression in the transfer function block and connect the transfer function block as shown in the attached circuit and you should get the same results.

[neomind]

Dear Tien P.

Tks for your help, that's right, but i don't want to inserte R3, i only want to simulate R+1/CS, how to do this ?

because the real circuit is more complex, R3 it's a big network with C,L,R and transformer, so to simulate mathematical function, not polinomial, i need first to know if R+1/Cs can be subtitued by laplace block

tks

best regards 

[Tien_P]

Hi Neomind,

You have to include the circuit load when using the transfer function block; I can't see a way to enter an expression without it.  

Going back to your original post, Multisim has components such as voltage control resistor, capacitor and inductor.  Using these parts along with components such as the Non Linear Dependent source, you can control the RLC values using a math expression.  Most, math expressions work in the time domain though.