Is there a rule of thumb way to determine how long the cable is on a cable reel?
Is there a rule of thumb way to determine how long the cable is on a cable reel?
(OP)
Our storeroom is filled with partially used rolls of cable that were left over from projects. In light of the high cost of copper it seems prudent to put it to use...except no one seems to know exactly how much is on the roll. There are generally tags on the reels to tell how much was originally on the reel....but this doesn't help a whole lot except to say the maximum amount.
Is there a way to do this? a chart..? a calc?
Is there a way to do this? a chart..? a calc?





RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
A Time Domain Reflectometer (TDR) can probe a shielded cable and determine the Electrical Length. If you can determine the Velocity Factor then you can then estimate the physical length to a fairly high accuracy (probably a few percent). It won't work reliably on unshielded wires where the coil would act like, well, a coil (inductor).
The normal method is to roll between reels with a foot counter clicking away.
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
This may be a good invention for somebody. I visualize something like an infrared meter or a digital tape measure would be handy.
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
It seems odd to me that you would suddenly need this level of accuracy on what appears to have been a rather willy-nilly process of cutting off lengths of cable without recording what was done.
TTFN

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RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
That's an ambitious 1% accuracy for a 1000-foot residual roll. I'd recommend you add something like "...or 5% (whichever is worse)" to your accuracy goal.
If there are a bunch that are the same type of wire and reel, then you could weigh full, unspool and measure, weigh the empty reel - all of just one example - and then weigh and calculate the rest (Y=mX+b). This should be quite accurate.
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
You obviously don't work in a union plant. I can't cut any cable myself or unreel it. If I were to get a work order to do this...it would involve an estimator, a foreman, an electrician and a part time safety person. Factor in work breaks and because this is odd ball work it would likely have to be done on a weekend...double time. And from my experience most jobs never take less than 1 day. And that doesn't count the paperwork and rigamarole I have to do. Come to think of it after explaining to the bean counters what I'm wanting to do and the cost...it would likely not be authorized.
And I really have no problem with the union. They do good safe work but its just how it is.
Your last point is well made though...there should be a procedure and documentation made up on how much cable is used on a reel and we wouldn't have this problem. There is not right now.
5% does sound like a better goal.
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
It'd be 'funny' (not really) if the foot marker numbers were there, but the other end was buried deep inside the reel.
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
That gives you a location for the bottom layer on the reel. You can then (most of the time) estimate how many layers on the reel. Then count the rows across. Calculate the average length of a turn and multiply.
If you need 400 feet then anything estimated below about 380 will be too short. Anything estimated above about 450 feet will be sufficient.
If the estimated length is between about 380 feet and 450 feet, you will have to measure with a more accurate method.
Bill
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"Why not the best?"
Jimmy Carter
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
You can usually get +/-5% using 200 000 000 m/sek speed of wave.
If you need better accuracy, just measure a 10 m cable to calibrate your readings.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
Z
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
Cheers
Greg Locock
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RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
If the wire is smaller guages and you can access the middle then use a low resistance ohm meter and measure the resistance and then calculate the length using wire resistance charts.
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?
RE: Is there a rule of thumb way to determine how long the cable is on a cable reel?