How to check continuity

[dsanthosh67]

Hi all,

Actually i need to check the continuity of a set of wires which is connected in parallel like the below image here.This is almost similar to the defogger lines in the car rear window glass.Kindly give me a suggestion how to verify all wires are connected, i need to identify if any wire is broken.

 

[chuckey]

The obvious way is to measure the resistance of the cables. If a conductor is broken it will have a 10% higher resistance. Another way is to check that each conductor has current flowing through it. Can you get a clamp-on ammeter on each conductor? if the conductors are un-insulated then measuring the voltage on the centre of a conductor should be 1/2 of the voltage drop across the whole cable. If a conductor is broken then it will be a different value ( 0V or voltage drop voltage).
Frank

 

[dsanthosh67]

Thanks for the reply,
I think based on resistance, its not possible to check the broken wires because the over all resistance is below 1 ohm.Even through the vary of resistance can find out there is a broken but how to find which wire is broken.
Another way current sense is possible but i am not able to clamp ammeter, is there any non contact current sensor.

 

[betwixt]

Connect a signal source at say 5 KHz across the feed points and use a magnetic pickup and audio amplifier to follow the wires. The current through good wires will induce a signal into the pickup, the broken one(s) won't.

Brian.

 

[dsanthosh67]

Thanks you,

I think its works fine but i have one more thing in this application. I need to measure the total ohms of the wires so i decided to apply a constant current source of 1mA and measure the value and also ensure the connectivity of wires is the another parameter.Already there is a 1mA current source,if i want to apply 5KHz signal means i need to do some other connection changes.Is there any feasibility in 1mA source itself.

 

[BradtheRad]

is there any non contact current sensor.

A compass is a method which has worked since olden times.

 

[betwixt]

It depends on the resistance of the wires and the sensitivity of your voltmeter. At 1mA, the voltage drop across the wires is only 1mV/Ohm and you have stated the resistance is less then 1 Ohm already. You are heading into the problem of being able to measure small voltages instead of small resistances. You might get more accurate results if you increase the current to say 100mA or even more but without knowing the wire size and environment you might start to risk heating effects.

Brian.

 

[dsanthosh67]

For resistance am clear here current is not a problem even it can increase to 100mA like you have stated, the only thing is connectivity.But you already mentioned that applying a 5KHz signal with magnetic pick up for connectivity instead, is there any possibility to ensure the connectivity by using only the current source.

 

[BradtheRad]

Fis there any possibility to ensure the connectivity by using only the current source.

Chuckey's suggestion (post #2) has the advantage of being simple and reliable.

if the conductors are un-insulated then measuring the voltage on the centre of a conductor should be 1/2 of the voltage drop across the whole cable. If a conductor is broken then it will be a different value ( 0V or voltage drop voltage).

 

[dsanthosh67]

Thanks for your valuable suggestions i work out with that and get back to you.

Santhoshkumar.