Cable conductors carry power, signal, or ground path current depending on cable assembly application.
Selection is based on mechanical and electrical properties. Solid and stranded wires are available. Materials used are usually copper with coatings such as silver or tin.
Larger AWG = less attenuation.
Smaller AWG = more flexibility.
Higher strand count = more flexibility.
The dielectric material, which acts as a buffer between the conductor and shielding components, allows the cable to maintain consistent electrical properties and minimizes signal loss.
The material can be either solid or foamed. This is where the dielectric constant (Er) defined below comes into play. The foaming of the dielectric is also important for keeping Er to a minimum. Some dielectric constants are listed below:
- Polyethylene, Er = 2.3
- Fluorinated Ethylene Propylene (FEP), Er = 2.2
- Solid FEP, Er = 2.1
- Polytetraflouroethylene (TFE, Teflon), Er = 2.1
- PVC, Er = 4 to 5
The cable jacket is an additional form of insulation as well as a protectant against environmental dangers.
A jacket typically is made of PVC, polyethylene, or FEP. The material used will determine the jacket’s temperature rating as well as minimum and maximum operating temperatures.
- PVC – Good weathering and abrasion resistant.
- Teflon – Ability to withstand high temps and chemically inert.
- Crosslinked PVC – Irradiation vinyl jacket has superior mechanical properties and short term heat resistance.
A cable consisting of two cylindrical conductors with a common axis, separated by a dielectric.
High speed applications.
Advantages: High longitudinally flexibility, variety of impedance options, high temp, abrasion resistant.
Disadvantages: Higher cost than PVC ribbon.
A system for circuit identification through use of solid colors and contrasting tracers.
An uninsulated wire suitable for carrying electrical current.
A tube or trough in which insulation wire and cables are run.
A device used to physically and electrically connect two or more conductors.
A test to determine whether electricity current flows continuously throughout the length of a single wire or individual wires in a cable.
An arrangement of wires and cables, usually with many breakouts, which have been tied together or pulled into a rubber or plastic sheath, used to interconnect an electric circuit.
A test designed to determine the electrical integrity of an insulation.
A single insulated conductor used for low-current, low voltage (usually under 600 volts) applications within enclosed electronic equipment.
The total opposition that a circuit offers to the flow of alternating current or any other varying current at a particular frequency. It is a combination of resistance R and resistance X1 measures in ohms.
High speed single ended driven applications, microwave, RF transmission, Internet and other applications requiring high bandwidth.
Advantages: Better performance over controlled impedance ribbon.
Disadvantages: Generally lower density because of single conductor.
A flat cable of individually insulated conductors lying parallel and held together by means of adhesive or woven textile yarn.
Internal applications, repeated flexing, printers, scanners, EIDE cables, .025″ CC and below.
Advantages: Typically low cost, high longitudinal flexibility, variety of dielectrics and cable pitches available.
Disadvantages: Not easily shielded, normally internal applications, difficult to route, low speed applications.
A metallic layer placed around a conductor or group of conductors to prevent electrostatic interference between the enclosed wire and external fields.
Shielding materials protect against signal loss and help prevent electromagnetic interference and radio-frequency interference in the circuit.
Several combinations of foils and/or braids are used to achieve various levels of shielding performance. Some shield examples follow:
- Single Round Braid – Excellent.
- Double Round Braid – Excellent.
- Spiral Wrap Shield – Good.
- Alum/Polyester Foil – Good.
- Helical Ribbon Foil – Good.
- Flat Braid Alum/Poly/Foil – Excellent.
Spiral wrap foils are most flexible.
Longitudinal wrap foils – better performance/ less flexible.
Braid Shield offer 95 to 98% coverage. Semi rigid are best but least flexible.
The physical area of a cable that is actually covered by the shielding material and is expressed in percent.
High speed data transmission.
Advantages: Further reduces pair to pair crossialk over UTP and adds additional protection against EMI.
Disadvantages: Automated processing is difficult.
A conductor composed of individual groups of wires twisted together to form an entire unit.
Tin coating added to copper to aid in soldering and inhibit corrosion.
Twinaxial cable is coaxial cable that contains two inner conducting wires rather than one. Used in high speed data transmission and differential driven applications.
Advantages: Easy to terminate, more consistent electrical parameters.
Disadvantages: Not many standard constructions.
Low speed data transmission, analog and digital applications and differential drive.
Advantages: Reduces crosstalk or electromagnetic induction between pairs or wires, as two insulated copper wires are twisted around each other.
Disadvantages: Automated processing is difficult.
Abbreviation for Underwriter Laboratories, a non-profit independent organization, which operated a listing service for electrical and electronic materials and equipment.
A flammability rating established by Underwriters Laboratories for wires and cables that pass a specially designed vertical flame test, formerly designated FR-1.
A single conductor, typically with a covering of insulation.
A measure of the diameter of sizes of wires. The sizes are expressed by numbers.