help me to deisgn the crcuit of resistance part

[aameer]

hello friends i want to measure the distance of cable fault .i found this link useful.can anybody show me how they have designed resistors and switches. Please help me. Check this video

 

[Reloadron]

They don't mention what the circuit is based on. Systems that look for faults in cables usually use a time-domain reflectometer (TDR) is an electronic instrument that uses time-domain reflectometry to characterize and locate faults in metallic cables. You can read about TDR here. Also this link provides a good writeup on the theory behind TDR. Again, in your link they do not cover the principal they use. The switches simply simulate a fault at a given distance to check the unit. Once you understand TDR then you will understand how faults can be simulated.

Ron

 

[aameer]

they have simply used 1k resistors and switches in series or parallel .and measured the voltage drop throuogh adc it seems

 

[Reloadron]

they have simply used 1k resistors and switches in series or parallel .and measured the voltage drop throuogh adc it seems

That sounds like a very good possibility.

Ron

 

[aameer]

Reloadron
Please provide me the circuit how to connect resistors and switches so that i can interface it to the adc and measure

 

[Reloadron]

The resistor matrix was suggested by aameer:

they have simply used 1k resistors and switches in series or parallel .and measured the voltage drop throuogh adc it seems

I agree it sounds logical but have no idea how they may have matrixed the resistors or if they are even all 1 K Ohm resistors.

Ron

 

[JimB]

As far as I can tell, the project in the video is measuring the resistance of the cable to the "fault" location.

To be able to do this, one would need to know the loop resistance per kilometre of the cable, other wise what value of resistance you need to find is unknown.

Consider the nature of the "fault".
If the fault is a very low resistance short circuit, the project will work as described by measuring the loop resistance to the fault.
However if the fault is an open circuit, it cannot work.
Similarly if the fault is of some intermediate value of resistance, the fault location cannot be calculated.

My opinion is that this is one of those academic projects which has no practical application and would be useless in the real world.
Why would you want to copy it?

The find cable faults, open circuit, short circuit, or something in between, use a Time Domain Reflectometer.

JimB

 

[Tony Stewart]

I agree Jim.
This a Mickey Mouse concept of an Ohms vs distance. In reality , transformers will shunt the line resistance at both ends as well for shorted lines an not detect line to line shorts.

TDR concept is the way to measure fault distance.

I noticed my ASUS MOBO BIOS uses this to measure ethernet port length, if enabled to display on boot.
Mine shows 0.6 m for a 1m cable.

 

[aameer]

thanks for all replies. I just want this project for college level not for real time. So i want the circuit with resistance and switches.Just for demonstartion. Please tell me how to connect resistors and switches.whether in series or parallel

 

[Tony Stewart]

The ADC uses a window comparator and an assumption of Ohms per km to quantize the line length. by sending a small constant current.

So a shorter length will short to ground along the loop, a smaller resistance., smaller voltage.


Ideally this should be AC constant current and not DC.

 

[aameer]

Friends make to design the circuit please.its urgent

 

[Reloadron]

This is your college level project. There is no urgent unless you have failed to do the required work. You were told to read up on TDR which apparently you have not done. I don't think anyone here will do your assignments for you.

Ron