# Auto Impedance Circuit

Discussion in 'General Electronics Chat' started by Engr, Feb 7, 2011.

1. ### Engr Thread Starter Member

Mar 17, 2010
114
5
Hi Guys. I am looking for a sample of an auto impedance circuit and how it will function. I was searching on the internet but found none. Can someone give me a sample of this kind of circuit and how it works?...Thanks

Apr 20, 2004
15,815
293
3. ### Engr Thread Starter Member

Mar 17, 2010
114
5
No. It is not related to my other thread. For this thread I want to know how to use the auto impedance circuit since this is the first time I learned about it. The other thread, I am trying to find a way to measure inductance, capacitance and resistance.....

4. ### Papabravo Expert

Feb 24, 2006
11,760
2,487
Now I've never heard of an Auto Impedance circuit. You might get more help if you explain what you think it is and what you need it for. We might actually know it by another name. This is especially true for translations form other languages. If we don't know where you are from it is hard to speculate on this possibility.

5. ### Engr Thread Starter Member

Mar 17, 2010
114
5
It is hard for me to explain what it is since I don't have any idea about it but to my understanding, it is like a Wheatstone bridge circuit I am just not sure. I need it to measure a very small resistance to get the value of any path resistance...

6. ### Papabravo Expert

Feb 24, 2006
11,760
2,487
The use of the word impedance implies the presence of reactive components like inductors and capacitors. If you are working only with resistance, then that is different. Measuring a small resistance is not remarkably different from measuring any other kind. The purpose of a bridge circuit is to compare an unknown resistance value to a known one. Two identical circuits with the same currents and voltages MUST have the same resistance.

I am curious about the meaning of "Auto Impedance Circuit" -- Anybody?
BTW, congratulations YOU are the #1 Google Hit. Not an easy feat in this day and age.

7. ### jpanhalt Expert

Jan 18, 2008
6,468
1,257
I thought he meant auto-ranging or auto-balancing, but apparently that is not the case. The other thread cited by beenthere addresses those aspects. I guess this thread could be called a double-blind question -- neither the OP nor anyone on the forum seems to know what the question is.

John

8. ### Engr Thread Starter Member

Mar 17, 2010
114
5
That is the reason why I said in my previous post that I am not sure how the circuit works, my goal for now is to measure a very small resistance but if the design will work then we will apply it to measure the impedance of capacitors and inductors. The wheatstone bridge is just an idea to start with the design but I am not sure if that will work. Sometimes we call it auto balance circuit. I dont have any idea on how to make the design, I have made several research but found none. If I cant find any idea on how to make the circuit then I guess I just have to stop making the design....

9. ### russ_hensel Distinguished Member

Jan 11, 2009
825
57
Perhaps auto is a reference to a car?

10. ### Engr Thread Starter Member

Mar 17, 2010
114
5
Nope. It is a reference to Automatic....

11. ### kubeek Expert

Sep 20, 2005
5,297
996
Engr: I think you need to think about what you actually want. Is that auto impedance circuit something you heard about and want to build it?
Or do you just want to build an autoranging RLC meter?

12. ### Engr Thread Starter Member

Mar 17, 2010
114
5
The RLC Meter is a different project, but if the auto impedance circuit can be applied to the RLC Meter and it will make the meter more accurate then I guess I will apply it. For now I don't have any plans on incorporating the auto impedance circuit to the RLC Meter.

13. ### kubeek Expert

Sep 20, 2005
5,297
996
So the term auto impedance is something you call it, or someone told you that? Either say what it is supposed to act like, or ask the guy who told you about it what it is.

This is what I found for automatic impedance, and I don´t think any of those is the right one.
- automatic impedance detection in cables
- automated measurement of pcb traces
- medical works in audiometry

Last edited: Feb 9, 2011
14. ### jpanhalt Expert

Jan 18, 2008
6,468
1,257
Engr likes this.

Sep 20, 2005
5,297
996
16. ### Engr Thread Starter Member

Mar 17, 2010
114
5
Thanks guys. The notes really helped me a lot. I appreciate it. Just have to consolidate all the notes to come up with a good design...