Hi!

What metering equipment can I use to measure the actual length of a cable inside a big drum without necessarily having to rewind on a counter meter. (Since the two ends of the cable will be exposed while inside the drum.)

Thanks
Chidi

Hello Chidi,

Could you please tell us what you mean by the expression ""inside a big drum".

Do you mean that the cable is already spooled on a big reel (Say with a 2 meter drum diameter and a flange diameter of above 4 meters.)

How big is the conductor?

Are there a number of cable layers and is the cable properly layer wound?

What is the length accuracy you are looking for?

Please advise. Thank you.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212

How about determine the weight of a similar empty wire container or "the big drum".

Determine the total weight of the drum with wire.

Subtract the empty drum weight from the full drum. this will equal the weight of the wire.

Cut a length from the wire; one foot, one yard, or meter. Weight that length.

Divide that length into the weight of the wire. If you weight a single foot of wire and it weights .25 kilos and the wire weights 2,000 kg then when you divide the 2,000 by 0.25 you will get 8,000 feet.


The only metering device you need is a scale that can measure the full drum and accurately measure a short length.

I received a private message from CHIDIEBEREAFOR. Since we don't respond to private messages, I have posted part of his message here:

"When a cable is spooled in a big reel say 2m reel (flange diameter).If you cannot take it to the factory where you can rewind on a counter meter, what other equipment can you use to determine the correct and actual length of the cable by simply testing the two exposed terminals. The cable could be insulated or bare conductor. Say you want to by a conductor inside a wooden drum and you are told that the length inside is 4km. How can you verify if you cannot take it to a factory to rewind?"

Hello again,

Bare Conductor
First of all, the length of bare conductor on a reel or spool cannot be measured electrically or electronically because the various layers and adjacent horizontal winds all short circuit each other. Moreover the bare conductor will likely short to the metal reel. The only way to determine the length on the reel is by knowing the net weight of conductor left on the reel as already discussed.

Jacketed Cable
It is unlikely you can electronically determine the length of a cable accurately in the field because of the very low resistance of the conductor. Thus the best way to determine how much cable is left on a reel is to specify sequential length marking (printing) on the surface of the jacket when the cable is manufactured.

Although a sequential length ink jet (surface) print on a jacket is usually the most accurate process, it is easily rubbed off or faded by the sun. To counter these problems, indent sequential marking, with ink or perhaps foil, is generally specified. This process however is less accurate, depending on the attention paid by the cable manufacturer and the error can be as much as +/- 2%.

Another method is to have the cable manufacturer place a length measuring tape longitudinally under the jacket. This means however that the cable must be opened and the jacket cut back to determine the length marking on the tape. Thus it is usually considered quite impractical.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212