PVC jacket
On the surface, it can be seen that there is a regular "unevenness" of the woven mesh inside the compression, indicating that the processing technology is good, there will be no relative sliding, and it is a good cable. The appearance is smooth, and the "unevenness" of the compressed braided net cannot be seen, and the sheath is loose when pinched by hand, which is a poor cable.
Check shield braiding. Is the number enough? Copper braided mesh, check the solderability, scrape the tinned copper wire to see if it is copper wire, the hardness of aluminum-magnesium alloy wire is obviously greater than that of copper wire; the braided mesh is sparse, uneven distribution, and the insulation layer is not tightly wrapped, etc. cable.
Check the core
Diameter — SYV cable is 0.78-0.8mm, SYWV cable is 1.0mm; there is a SYV75-5 cable with a core wire diameter of 1.0mm, the characteristic impedance of this cable is definitely not 75 ohms, it should not be applied to 75 ohms in the transmission system.
Check core and insulation adhesion. Cut the insulating layer diagonally, pull the core wire in the peeling direction, and check whether the core wire and the insulating layer are adhered to the process material; the good cable has a large adhesion force, and the poor cable does not adhere.
Longitudinal tensile test. Take one meter of cable, strip the core wire, insulating layer, shielding layer, and outer sheath in layers, leaving 10 cm long for each. The method is: hold the two adjacent layers of the cable with two hands and pull them in opposite directions; good cables cannot be pulled with general force, but poor cables can be easily pulled out without much effort — elevator cables are very important, and many so-called "Elevator special cables" all have this problem.
