Visual Inspection for Cable Quality:
1. PVC Sheath: A high-quality cable will have a smooth surface with a consistent inner mesh structure, showing no signs of irregularities or looseness. If the sheath feels loose when pinched, it’s likely a low-quality product. A well-processed cable will not show visible unevenness in the inner layer.
2. Shielding Layer Check: Look at the copper mesh inside. A good cable will have dense and evenly distributed shielding, with proper tinning on the wires. Poor quality cables may have sparse mesh, uneven distribution, or even aluminum-magnesium alloy wires, which are harder than pure copper. These materials can reduce signal performance and durability.
3. Core Wire Diameter: For SYV cables, the core diameter is typically between 0.78–0.8mm, while SYWV cables usually have a 1.0mm diameter. Recently, some 75-5 cables with a 1.0mm core have been seen, but their impedance may not be accurate, making them unsuitable for 75-ohm systems.
4. Adhesion Test: Cut the insulation layer at an angle and pull the core wire in the direction of peeling. If the core and insulation stick together, it indicates good adhesion. If they separate easily, the cable is likely substandard and lacks proper bonding during manufacturing.
5. Longitudinal Tensile Test: Take one meter of the cable and strip each layer (core, insulation, shielding, and outer jacket) for about 10 cm. Hold two adjacent layers and pull them apart. A good cable should resist this force, while poor-quality cables will come apart easily. This test is especially important for elevator cables, as many so-called "elevator-specific" cables fail this check.
Fire Test for Copper Wires:
It's challenging for consumers to tell if a cable uses real copper or fake materials. There are various types of counterfeit copper wires available, and some are very hard to detect. Here are three common types:
1. General Fake Copper Wires: These include copper-clad aluminum, copper-clad magnesium-aluminum alloy, copper-clad steel, and copper-clad iron. They look similar to real copper but are much cheaper and less conductive.
2. High-Imitation Fakes: These wires contain a mix of real copper and copper-clad alloys. They are more expensive and harder to spot, but still lack the conductivity and durability of pure copper.
3. Non-Standard Wires: These are made from low-quality materials, often not drawn from oxygen-free copper. They may have fewer strands or poor transmission properties, leading to signal loss or failure over time.
If you're unsure about the type of copper wire, a simple fire test can help. Take a small piece of the exposed copper wire and burn it with a lighter. Real copper can withstand high heat for over a minute without melting. However, copper-clad aluminum or copper-clad steel will bend or melt quickly. This method is effective for identifying genuine versus fake copper in SYV, RVV, and similar cables.
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