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1. 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 net cannot be seen, and the sheath is loose when pinched by hand, which is a poor cable.
2. Check the screening braid
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.
3. Check the core wire
Diameter – SYV cable is 0.78-0.8mm, SYWV cable is 1.0mm; recently, an SYV75-5 cable with a core diameter of 1.0mm has appeared. The characteristic impedance of this cable is definitely not 75 ohms, and should not be applied to 75 ohms. In the ohmic transmission system.
4. Check the adhesion between the core wire and the insulation layer
Cut the insulating layer obliquely, and pull the core wire in the peeling direction to see if the core wire and the insulating layer adhere to the process material; the good cable has a large adhesion force, and the poor cable does not adhere.
5. Longitudinal tensile test
Take one meter of cable, peel off the core wire, insulation layer, shielding layer, and outer jacket in layers, leaving 10 cm long for each. The method is to hold the adjacent two layers of the optical fiber cable with two hands, and pull in opposite directions; good cables cannot be pulled with a general force, but poor cables can be easily pulled out without much effort-the elevator cable is very important, not Less so-called “elevator special cables” have problems in this regard.