Security monitoring cable quality is good or bad how to identify
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In engineering practice, how can we identify good and bad?
1. PVC jacket: The surface can see the regular "unevenness" of the netting inside the net, which means that the processing technology is good and no relative slipping will occur. It is a good cable. The appearance is smooth, can't see the "unevenness" of the compacted net, and the looseness of the sheath is caused by hand, which is a poor cable;
2, check the shielding layer mesh: whether the number is enough? Copper wire mesh, check the solderability, tinned copper computer wire scraping to see if it is copper wire, aluminum-magnesium alloy wire hardness is significantly greater than the copper wire; network sparse , uneven distribution, and the insulation layer is not tight, such as poor cable;
3, check the core: diameter - SYV cable is 0.78-0.8mm, SYWV cable is 1.0mm; recently appeared a SYV75-5 core diameter is 1.0mm cable, the characteristic impedance of this cable, certainly not 75 Ohm, not applied to 75 ohm transmission systems;
4. Check the binding force between the core wire and the insulating layer: Cut the insulation layer obliquely, pull the core wire in the direction of peeling, and see if the core wire and the insulation layer are covered with the process material; good cable has a large binding force, poor The cable is not covered;
5. Longitudinal tensile test: Take one meter cable, peel the core wire, insulation layer, shielding layer, and outer cover in layers, leaving 10 cm long. The method is: Two hands hold the adjacent two layers of the cable and pull in the opposite direction; the cable is generally unable to pull the power, so the cable can be easily pulled out without any effort.