finding impedance between two point

Status
Not open for further replies.
A

akbarza

Full Member level 2
Joined
Dec 18, 2013
Messages
131
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,296
Activity points
2,556
hi
Maybe this question is stupid and simple, but I'm stuck on it.
in the below pic, how can i calculate impedance between the two points a and b?
again, i think it is a stupid question, but i trapped in it for 1 hour.
thanks
--- Updated ---

hi again
i wanted a formula that express equal impedance in c's and r's and how this formula is gained.
thanks
 

Attachments

  • impedence_finding.png
    19.5 KB · Views: 117
Last edited:

Sort by date Sort by votes
Hi,

Point A is driven by a device. This device also refers (impedance) to GND (and VCC) like R1 does.
So if you really want to know the complete impedance of A to B you need to know the source impedance (into A), too.

If you don´t want to involve the source, then you also probaly don´t want to involve R1, too (because both refer to GND).

In this case: impedance is : (XC1 + R2) || R3

Klaus
 

Upvote 0 Downvote
hi
i upload a new pic.
--- Updated ---

hi
i upload a new pic.
--- Updated ---

hi
i upload a new pic.
--- Updated ---

hi
i upload a new pic.
--- Updated ---

hi
i upload a new pic.
--- Updated ---

i tried several times to upload a file, but i am failed.
in the the pic , i want v(N)/v(T)
 

Attachments

  • file2.png
    60.5 KB · Views: 249
Last edited:

Upvote 0 Downvote
Transfer function according to Sapwin:

( R2 + R1) + ( Cf R1 R2 + Cf R R1) s
--------------------------------------------------------------------------
( R2 + R1) + ( Cf R1 R2 + Cf R R2 + Cf R R1 + Cn R R2 + Cn R R1) s + ( Cn Cf R R1 R2) s^2

 

Upvote 0 Downvote
akbarza said:
i tried several times to upload a file, but i am failed.
Click to expand...
What to do with this information? I don´t know what you did and what happened.

But uploding a picture shouldn´t be that difficult:
* press the [insert image] button
* press at (Or click here)
* chose your file
* press [post reply]

Klaus
 

Upvote 0 Downvote
If not specified IN- assumed to be infinite Z .....eg presents no load to network.

Do you want Vn(s) / Vt(s) or Vt(s) / Vn(s), as it appears to be a feedback network to IN-?

If former since Vt is a V source that means its Z is 0 therefore R & R2 junction is
grounded. There is no T(s) [transfer function] solution since Vt(s) = 0.

If latter Vt is driving point for transfer function then :



Since Vt(s) is the voltage source all you have to do is write node/loop equations to get at
Vn(s), assuming IN- is Zinfinite.


Regards, Dana..
 
Last edited:

Upvote 0 Downvote
Hi,

In post#1 I guessed the signal flow is standard: from left to right

But now the signal flow is right to left.

Klaus
 
Upvote 0 Downvote
KlausST said:
Hi,

In post#1 I guessed the signal flow is standard: from left to right

But now the signal flow is right to left.

Klaus
Click to expand...
And a capacitor is added
So I wonder if answering the question on post #1 is no more important (in which R1 has no role in the formula of Zab).
 

Upvote 0 Downvote
Regarding original question, the error of reasoning is to analyze the behavior of a tree terminal network as "impedance between two points. The a-b impedance depends also on source and load impedance.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…