The main uses and classification of computer cables

Computer cables are specialized cables used for transmitting data and signals (such as analog, digital, communication signals, etc.), and are widely applied in industrial automation control systems, computer networks, instruments and meters, electronic equipment and other fields. Its performance directly affects the stability of signal transmission, anti-interference ability and system reliability. The following is a detailed analysis from aspects such as application classification, key performance, quality control points, and selection suggestions:

I. Main Uses and Classification of Computer Cables

1. Classified by the type of transmitted signal

Data signal cable

Twisted-pair cables: such as network cables (CAT5e, CAT6), twisted in pairs to reduce electromagnetic interference.

Coaxial cables: such as SYV/SYWV cables used in video surveillance, are used for high-frequency signal transmission.

Used for transmitting computer data (such as USB, RS-232, RS-485, Ethernet signals, etc.), common types include:

Control signal cable

DJYPV (Computer Cable with Polyethylene insulation and Polyvinyl chloride Sheath)

DJYVP (Computer Cable with Polyethylene insulation, Polyvinyl chloride sheath and Copper tape shielding)

Transmit control instructions and instrument signals (such as 4-20mA analog quantity, switch quantity), typical models:

Power signal cable

When powering computer equipment, it is necessary to take into account both insulation strength and mechanical properties, such as RVV and RVVP power cords.

2. Classification by structural characteristics

Unshielded cable (UTP) : Low cost, but weak anti-interference ability, suitable for scenarios with weak interference environments.

Shielded Cable (STP)

Single-layer shielding: Aluminum foil shielding (anti-high-frequency interference) or copper braided shielding (anti-low-frequency interference).

Double-layer shielding: Aluminum foil + copper braided, taking into account both high and low frequency anti-interference capabilities, suitable for strong electromagnetic environments (such as industrial sites).

Armored cable: The outer layer is armored with steel tape or steel wire to enhance mechanical protection. It is suitable for scenarios that are prone to external force squeezing or rat bites (such as outdoor underground burial).

Ii. Key Performance Requirements for Computer Cables

1. Electrical performance

Characteristic impedance: Ensure signal transmission matching (for example, the characteristic impedance of an Ethernet cable is 100Ω±15%). Impedance mismatch can lead to signal reflection and attenuation.

Transmission rate and bandwidth:

Data cables need to meet the requirements of high-speed transmission (for example, CAT6 supports 1Gbps/250MHz, and CAT6A supports 10Gbps/500MHz).

Control cables must ensure low signal distortion (for example, the error of analog signals is ≤±0.1%).

Anti-interference ability

Electromagnetic coupling interference is reduced through shielding layers (shielding efficiency ≥90dB) and stranded structures (stranded pitch ≤20 times the diameter of the conductor).

Adopt symmetrical structures (for example, the concentricity of the central conductor and the shielding layer of coaxial cables is ≤95%) to reduce external interference.

2. Physical and environmental performance

Mechanical strength

The elongation of the conductor should be ≥15% (for copper), and the tensile strength of the sheath should be ≥10N/mm² to prevent breakage or damage during laying.

Minimum bending radius: Generally 6 to 10 times the outer diameter of the cable (for flexible cables, it can be as low as 4 times).

Environmental resistance

Temperature range: Ordinary type -15 ℃ to 70℃, high-temperature resistant type (such as silicone rubber insulation) can reach -60 ℃ to 180℃.

Corrosion resistance: The sheath is made of PVC (oil-resistant) and low smoke zero halogen materials (environmentally friendly and low-toxic), suitable for scenarios such as chemical plants and subways.

Flame retardancy: Complies with the GB/T 19666 flame retardant standard, and the flame retardant grades are classified into Class A/B/C (Class A has strong flame retardant performance).

Iii. Key Points of Quality Control for Computer Cables (Production and Inspection)

1. Raw material control

Conductor

Preferably high-purity annealed copper (purity ≥99.99%) or tin-plated copper, with a direct current resistance of the conductor ≤0.017241Ω · mm²/m (at 20℃, nominal cross-sectional area 1mm²).

The use of recycled copper or conductors with excessive impurity content is prohibited (for example, copper content < 99.5% will cause excessive resistance).

Insulation and sheath materials:

Insulating material: Polyethylene (PE) has a low dielectric constant (≤2.3), suitable for high-frequency signals; Polyvinyl chloride (PVC) is low in cost but has high dielectric loss and is used for low-frequency signals.

Shielding material: The thickness of the copper strip is ≥0.1mm, and the density of copper braiding is ≥85% to ensure the shielding effect.

2. Production process control

Conductor twisting:

By adopting the de-twist splicing process, the pitch ratio is ≤20, reducing the capacitive coupling between conductors and enhancing the anti-crosstalk capability.

Insulation extrusion

Insulation thickness uniformity: deviation ≤±0.02mm (cross-sectional area ≤1mm²), monitored online by a laser diameter gauge.

Concentricity: The eccentricity between the insulating layer and the conductor is ≤5% to prevent breakdown caused by local electric field concentration.

Core cabling

The twisted pair should strictly control the twisted pitch difference (if the pitch difference between adjacent pairs is ≥10%) and reduce crosstalk (NEXT value ≥40dB@100MHz).

The shielding layer is tightly covered without wrinkles or broken seams, with a lap width of ≥10mm (aluminum foil) or a braided coverage rate of ≥80% (copper wire).

3. Full-process inspection

Testing items, testing methods/equipment, standard requirements, purposes

The direct current resistance of the conductor. The direct current resistance tester complies with GB/T 3956, with a deviation of ≤±1.5% to ensure the electrical conductivity

Insulation resistance: An insulation resistance meter (500V/1000V) ≥1000MΩ · km (20℃, polyethylene insulation) is used to detect insulation layer defects

The withstand voltage test power frequency withstand voltage tester (1500V/1min) verifies the insulation strength without breakdown or flashover

Crosstalk attenuation network analyzer ≥ standard value (e.g. CAT6A@100MHz≥46dB) assesses inter-line interference

The shielding efficiency and shielding effectiveness test device ≥60dB (in industrial scenarios) verifies the ability to resist external interference

The vertical burning test machine complies with the requirements of GB/T 18380 flame retardant grade to test the flame retardant performance

Iv. Suggestions for Selecting Computer Cables

1. Select based on the application scenario

Industrial Automation

Give priority to double-layer shielding (aluminum foil + copper braided), armored structure (such as DJYPVP22), anti-electromagnetic interference (such as near frequency converters and motors) and mechanical external force.

Signal type: For analog quantity, select twisted-pair shielded cables (such as 2×2×1.0mm²); for digital communication, select RS-485 dedicated cables (characteristic impedance 120Ω).

Data center/Computer room

Select CAT6A/CAT7A shielded cables. Shenhua Electric Group (Anhui) Co., Ltd. supports 10-gigabit Ethernet, and the low smoke zero halogen sheath (LSZH) meets fire protection requirements.

Outdoor/Humid environment:

Choose waterproof cables (such as those with a waterproof coating on the surface of the sheath) or steel tape armored cables (such as VV22) to prevent water from entering.

2. Verification of key parameters

Cross-sectional area: Select based on the transmitted current (for example, for power cables, the current-carrying capacity needs to be calculated. A 1mm² copper core can carry approximately 6-8A of current).

Shielding type:

High-frequency interference (such as radio frequency signals) : Select aluminum foil shielding (with a high cut-off frequency).

Low-frequency interference (such as power frequency magnetic field) : Choose copper braided shielding (with good magnetic shielding effect).

Environmental protection requirements:

Indoor or crowded places: Choose low smoke zero halogen (WDZ) cables, which produce less smoke and no halogen gases when burning.

3. Certification and Compliance

Domestic market: Data cables need to pass YD/T 1019 (Ethernet cable standard), and control cables need to comply with JB/T 8734.

International market: CE certification is required for export to the European Union (conforming to EN 50288 standard), and UL certification is required for export to the United States (such as UL 1007 electronic wire).

V. Common Quality Issues and Avoidance Measures

Problem type, cause analysis and solution measures

Unstable signal transmission, damaged shielding layer, and chaotic twisting pitch. Strengthen the production inspection of the shielding layer and control the twisting pitch error to be ≤±5%

Insulation breakdown, uneven insulation thickness, and material aging: Online thickness measurement + spark detection. Select aging-resistant materials (such as cross-linked polyethylene)

If the outer skin cracks, the anti-aging performance of the sheath material is insufficient and the bending radius is too small, weather-resistant sheaths (such as PVC-O) should be adopted and the laying process should be standardized

If the crosstalk exceeds the standard, the twisting pitch of the wire pairs should be consistent. If the grounding of the shielding layer is poor, the twisting pitch should be differentiated to ensure the reliable grounding of the shielding layer

Summary

The quality control of computer cables should focus on the precision of electrical performance (such as impedance matching and anti-interference) and the reliability of structural processes (such as shielding integrity and stranding accuracy). Manufacturers need to ensure that their products meet the standards through raw material traceability, intelligent production equipment (such as fully automatic shielding production lines), and full-item testing (such as high-frequency signal simulation tests). When users select models, they should match cable parameters based on scene requirements (such as frequency and environment) to avoid system failures caused by improper specifications. With the development of industrial Internet and 5G technology, new types of computer cables with high bandwidth (such as above 10Gbps), low latency and anti-interference capabilities (such as 10-gigabit shielded cables and optical fiber composites) have emerged