First, you should observe the appearance of the cable. […]
First, you should observe the appearance of the cable. The insulating (sheath) layer of the qualified product will feel smooth and soft when touched by hand. With the nails, your surface will be elastic and the surface will be free of unevenness and stinging. If the outer layer of the insulation is easily peeled off, there is a problem that the strength and elasticity of the insulation are insufficient.
Second, look at the cross section of the cable. The surface of the conductor of the qualified product will directly see the shiny luster of the metal, and the gloss is softer. The surface of the dark-brown copper or the surface of the white aluminum has been oxidized.
Third, the product identification and other information provided should be carefully checked when purchasing the cable. If these are clear and in line with the standard, then the initial judgment cable should be tested and the quality is not bad.