Is there any way (with minimal/improvised equipment) to find a break in a main lead? I do at least own a digital multimeter.
It's the cable for an electric lawnmower, and it's got a few scratches and nicks in the outer insulation from being used outdoors.
I guess one of those nicks is "deep enough", because the lead no longer works.
I only want to cut and repair it in the right place, obviously...
Is there anyway I can send some kind of signal into the conductor, and detect where it stops?
My mind is groping at kind of AC+coil concept or radio+aerial concept.
Does such a thing exist that is easy/cheap to do?
Failing which I'll just buy a new lead, but it's 35 yards long, and 240v/10Amp rated, so not cheap.
BugBear
It's the cable for an electric lawnmower, and it's got a few scratches and nicks in the outer insulation from being used outdoors.
I guess one of those nicks is "deep enough", because the lead no longer works.
I only want to cut and repair it in the right place, obviously...
Is there anyway I can send some kind of signal into the conductor, and detect where it stops?
My mind is groping at kind of AC+coil concept or radio+aerial concept.
Does such a thing exist that is easy/cheap to do?
Failing which I'll just buy a new lead, but it's 35 yards long, and 240v/10Amp rated, so not cheap.
BugBear
Last edited:
Make a solutrion of sodium bicarbonate in a bucket.
Connect a plate of copper, brass, etc to one multimeter probe and immerse in the bucket/solution.
Connect other meter probe to both active and neutral wires of the cable.
Draw the cable slowly through the bucket/solution until you get conductance reading....there's your break.
Dan.
Connect a plate of copper, brass, etc to one multimeter probe and immerse in the bucket/solution.
Connect other meter probe to both active and neutral wires of the cable.
Draw the cable slowly through the bucket/solution until you get conductance reading....there's your break.
Dan.
Ah - in effect a liquid probe that will go through the hole? Ingenious.
Devil's advocate - if I've understood, it wouldn't detect a break caused by a properly insulated, but broken-by-fatigue cable, correct?
BugBear
The instrument you're questioning is called a "time domain reflectometer". These send a pulse down the wire which gets reflected back to the instrument where it shows on a screen. (CRT or LCD) Any aberration in the reflected pulse can be calculated in terms of time, and so distance, down the wire from the instrument. But these are mostly for coaxial or fiber optic cable and may not work well on plain power cables. And they are expensive.
If this were my faulty cable I would use low voltage (6V) with a small lamp on one end. Then with 6 volts applied to the opposite begin bending/flexing the cable at suspected locations and see if the lamp goes on. I have located breaks several times in wires this way. And it's very inexpensive too.
If this were my faulty cable I would use low voltage (6V) with a small lamp on one end. Then with 6 volts applied to the opposite begin bending/flexing the cable at suspected locations and see if the lamp goes on. I have located breaks several times in wires this way. And it's very inexpensive too.
I would put the cable at the output of a function generator set to some high frequency like 100k-1MHz and try to probe it along its length with a capacitive probe.
Failing that, if the nick is large enough: Max Headroom's solution, with a twist. Connect one end of the cable to +12V (all wires) and dip the negative of the 12V supply in the water. Add salt or other ions. Dip the whole roll of cable. Look for the place where hydrogen bubbles come out.
Failing that, if the nick is large enough: Max Headroom's solution, with a twist. Connect one end of the cable to +12V (all wires) and dip the negative of the 12V supply in the water. Add salt or other ions. Dip the whole roll of cable. Look for the place where hydrogen bubbles come out.
A very good idea, as you will find many uses for it. It could also save a life.
Mine is a Greenlee GT-11 Voltage Detector; the newest version is the GT-12A.
Greenlee GT-12A Voltage Detector, 50-1000V CAT IV Audible/Visual Self-Testing Non-Contact - AC $17.99
Try Home Depot if you have a local store, they carry Greenlee, might cost a bit more there.
I have used many types of these and the Greenlee has been the best.
Happy troubleshooting
Mine is a Greenlee GT-11 Voltage Detector; the newest version is the GT-12A.
Greenlee GT-12A Voltage Detector, 50-1000V CAT IV Audible/Visual Self-Testing Non-Contact - AC $17.99
Try Home Depot if you have a local store, they carry Greenlee, might cost a bit more there.
I have used many types of these and the Greenlee has been the best.
Happy troubleshooting
If your DVM has a capacitance scale then measure the capacitance of live-neutral from both ends of the cable (after disconnecting it from the appliance, of course - unless you can be sure that the switch does this). An intact cable should give nearly the same reading from both ends, as will a cable with a break exactly in the middle. A significant difference will show you where the break is.
For example, if you measure 200pF from one end and 500pF from the other end then this means that the break is 2/7 of the way along from the low capacitance end. Once repaired you should measure 700pF from both ends. Snag: this assumes that no moisture has entered the cable - so do this before playing with bicarbonate solutions!
For example, if you measure 200pF from one end and 500pF from the other end then this means that the break is 2/7 of the way along from the low capacitance end. Once repaired you should measure 700pF from both ends. Snag: this assumes that no moisture has entered the cable - so do this before playing with bicarbonate solutions!
Agree, I do that on long Guitar or Microphone cables: measure capacitance on one end , then on the other.
If I see about same value, say 250pF / 250pF then both capacitors are the same, so break is in the exact middle.
If one is twice the other, then it´s at 2/3 length and so on, simple Math.
If it broke near one end, you will measure, say, 400pF and less than 50pF , which is the probe or clip capacitance.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.