1, check the shielding layer network: whether the number is enough? Copper wire mesh, check the solderability, tinned copper computer wire scrape to see if it is inside the copper wire, the hardness of the aluminum-magnesium alloy wire is significantly larger than the copper wire; The distribution is uneven, and the insulation layer is not tightly wrapped, etc. It is a poor cable; if it is a copper-clad aluminum, it is easy to see that the internal color is different from the outer copper; peeling off the outer skin and seeing the shielding layer If the weaving angle is basically upright, then basically we can see that the weaving angle is large, which is a product for cutting corners;

2, PVC sheath: the surface can be seen to press the inside of the net has a regular "unevenness", indicating that the processing technology is good, will not produce relative sliding, is a good cable. The appearance is smooth, and the "unevenness" of the compacted net is not seen. The hand-pinched jacket has a loose feeling, which is a poor cable;

3. Check the adhesion between the core wire and the insulation layer: cut the insulation layer obliquely, and pull the core wire in the peeling direction to see if the core wire and the insulation layer are in contact with the process material; the cable has a large adhesion force and difference. The cable is not glued;

4, check the core wire: diameter - SYV cable is 0.78-0.8mm, SYWV cable is 1.0mm; recently appeared a SYV75-5 core wire diameter of 1.0mm cable, the characteristic impedance of this cable, certainly not 75 Ohm, not applied to a 75 ohm transmission system; use a vernier caliper to check the diameter of the cable core;

According to national standards, cable costs generally reach 2.25 yuan / meter, but it is not excluded that some suppliers in order to meet the low price psychology of the contractor to produce cables for cutting corners, so wide eyes, carefully identify the advantages and disadvantages of cables .