How to determine the cross-section of the wire and cable cores. 3 easy ways

  • Dec 14, 2020
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Sometimes it is necessary to replace the damaged wire very quickly, but the most difficult thing is not to dismantle the product, and not to lay a new one, but to determine the cross-section of the conductors. And if 1.5 and 2.5 cm2 can still be determined "by eye", then with such a cross section as 0.5 cm2 this will not work. In this situation, you should remember 3 simple ways to determine the cross-section of a wire or cable.

Method number 1: using a ruler, pencil and simple formula

It is better to immediately describe the sequence:

  1. Remove the insulation from a small piece of conductor (no more than 10-15 cm).
  2. Wrap 15-20 turns of wire around the pencil.
  3. Measure the entire length of the resulting structure with a ruler and divide it by the number of turns. The answer is the diameter of the core.
Figure 1: Defining the section with a pencil and ruler

After obtaining the diameter, you need to find out the section, and for this, apply a simple formula:

S = 0.785 * d * d; where S is the cross-section of the core, d is its diameter.

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If the result is not accurate, then it should be rounded to the nearest value defined by GOST.

Method number 2: using a piece of paper

Not as popular as the previous one, but still takes place in the everyday life of electricians. It is possible to determine the cross-section of the conductor with a piece of paper only if the conductor is large enough; in other cases, a seemingly simple operation is complicated by the small size of the core.

How to determine the cross-section of a wire using a piece of paper:

1. Attach a small piece of paper to the wire and wrap it until the ends touch. The resulting distance is the circumference.

Figure 2: Just a simple piece of paper

2. Find the diameter of the core using the length, using the following formula: d = l / 2n, where d is the diameter of the core, l is the circumference, n is 3.14.

Figure 3: The circumference of the core will remain on the sheet

3. Substitute the value in the formula (S = 0.785 * d * d) and find out the cross-section of the core.

Not too simple, but when there are no additional measurement tools at hand, then this method is not bad either.

Notes: all photos are original from my site: https://www.asutpp.ru/kak-opredelit-sechenie-provoda-ili-zhil-kabelya.html

Method number 3: when you have a caliper at hand

Almost every second electrician has a vernier caliper at hand, fewer carry a micrometer. The first and second tools are very useful things in the everyday life of an electrician, so they should be purchased, just in case.

To determine the cross-section of the wire using a caliper or micrometer, you must:

  1. Remove the insulation from the core.
  2. Move the measuring ends of the caliper apart to the sides and bring them together again, holding the conductor core between them.
  3. Read the wire diameter on a caliper scale.
  4. Using the formula (S = 0.785 d2), determine the cross-section of the veins.

A caliper or micrometer may not be at hand, so it is better to resort to one of the two methods given above. Items such as paper, pencil and ruler are almost always at hand.

How else can you determine the wire size

Just by looking closely at the insulation, which usually displays the following information:

  • Wire type.
  • Manufacturer.
  • Number of lived.
  • Section.

The easiest and most convenient option, unless, of course, the insulation is so damaged that it is not possible to make out the designation on it.

See more information in my video, where not 3 but 6 ways to determine the cross-section of a wire or cable cores are presented: