Resistanc and capacitance extraction

[Junus2012]

Dear friends and teachers

in this image , a block with internal capacitance and resistance. Kindly, what is the simulation and measurements method to extract the value of both

Note: consider please the only two ports from the circuit

Thank you

 

[albert22]

You can excite with an AC voltage source and measure the current or use a current source and measure the voltage.
then you know that:
V/I = Z = R/ (1+ jwRC) that is the impedance of the RC circuit.
w = 2* pi * frequency
Take into account that V, I and Z are complex numbers. So you have to measure magnitude and phase.
Calculate V/I from your measurements. You also know at what frequency the measurement took place.
Rearrange the expression of Z and convert V/I so both have the form a+jb.
Re(V/I)= Re(Z) -- gives R
Im(V/I)=Im(Z) -- knowing w allows you to calculate C.

Hope that this is not very confusing

 

[Junus2012]

dear albert

thank you for your explanation

But how you assured that the real part gives you only the resistance, i think it cant be coz

real = R/root(1+sqr(WRC)), so you see from the real part that both variables (R and C) are still together

You can excite with an AC voltage source and measure the current or use a current source and measure the voltage.
then you know that:
V/I = Z = R/ (1+ jwRC) that is the impedance of the RC circuit.
w = 2* pi * frequency
Take into account that V, I and Z are complex numbers. So you have to measure magnitude and phase.
Calculate V/I from your measurements. You also know at what frequency the measurement took place.
Rearrange the expression of Z and convert V/I so both have the form a+jb.
Re(V/I)= Re(Z) -- gives R
Im(V/I)=Im(Z) -- knowing w allows you to calculate C.

Hope that this is not very confusing

 

[albert22]

I see the point. The eq. gets complicated.
Try using the admittance:
I/V= 1/Z=Y= (1/R)+( JwC)
Z should give the same results I will to try to solve it.

 

[alexan_e]

duplicate of https://www.edaboard.com/threads/277026/

thread locked