Elec Cables (1)

8/2/2019 Elec Cables (1)

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CABLES INTRODUCTION

What is a cable?Two or more wires running side by side and bonded, or twistedtogether to form a single assembly

In mechanics, known as wire ropes - used for lifting, hauling and towing force through tension.

In electrical engineering - used to carry electric currents.

In electronics used for transmitting audio, video and data signalsfrom input to output.

Most cables designed to carry more than one message at an instant.


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SOME properties and usesOF Electrical cables

Flexibility - Stranding of wires by twisting or bunching smallerindividual wires to produce larger wires, to produce similar results.

Safety :Securely fastened and organized

Skin effect: Tendency of the current to run along the surface of the

conductor at high frequencies.

Utilities:

Tanning and Soldering.

Installation in buildings and industrial sites.


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TYPES OF CABLES

1. Optical Fiber Cables

2. Coaxial Cables

3. Ribbon Cables

4. Twisted Pair Cables


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OPTICAL FIBRE CABLES


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INTRO - OPTICAL FIBRES

Flexible, transparent fiber made of pure glass (silica).

Transmit messages in the form of light.

Functions as a waveguide, or light pipe, between the twoends of fiber.

Permits effective transmission over other forms ofcommunication:

over longer distances

at higher bandwidths

Improvement over usage of metal wires :

Avoids signal loss upon travel.

immune to electromagnetic interference.


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CONSTRUCTION OF A FIBRE

Consists of a transparent core surrounded bytransparent cladding material.

Light kept in the core by total internal reflectioncausing the fiber to act as a waveguide.

Multi-mode fibers (MMF) - Fibers that support manypropagation paths or transverse modes. Used for short-distance communication links and for applicationsrequiring high power transmission.

Single-mode fibers(SMF) - Used for most communicationlinks longer than 1,050 meters (3,440 ft).


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Applications

Used as a medium for telecommunication and computernetworking due to flexibility and can be bundled ascables, thus advantageous for long-distancecommunications, as light propagates through the fiber withlittle attenuation compared to electrical cables.

Used to connect a non-fiber optic sensor to ameasurement system.

Determination of time delay using a device such as anoptical time-domain reflectometer.

Fibers are widely used in illumination applications. Eg.Optical fiber illumination used in s= neon sign boards, art,toys ,artificial Christmas trees.

Used in imaging optics. A bundle of fibers is used, for a

long, thin imaging device called an endoscope, which isused to view objects through a small hole.


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Applications

In spectroscopy, optical fiber bundles transmit light from a spectrometerto a substance that cannot be placed inside the spectrometer itself, inorder to analyze its composition.

Supply around one watt to electronics situated in a difficult electricalenvironment. Example: electronics in high-powered antenna elements

and measurement devices used in high voltage transmission equipment. The iron sights for handguns, rifles, and shotguns may use short pieces

of optical fiber for contrast enhancement.


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MERITS OF OPTICAL FIBRES

Extremely high bandwidth No other cable-based data transmission medium offers thebandwidth that fiber does.

Easy to accommodate increasingbandwidth Using many of the recentgenerations of fiber optic cabling, newequipment can be added to the inert fiber

cable that can provide vastly expandedcapacity over the originally laid fiber.

DWDM, orDense Wavelength DivisionMultiplexing, lends fiber optic cabling the

ability to turn various wavelengths of light


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DEMERITS OF OPTICALFIBRES

Installation costs, while dropping, are still high Despite the fact thatfiber installation costs are dropping by as much as 60% a year, installingfiber optic cabling is still relatively costly.

Special test equipment is often required The test equipment typicallyand traditionally used for conventional electron-based networking is of no

use in a fiber optic network. Eg. OTDR (Optical Time DomainReflectometer)

Susceptibility to physical damage Fiber is a small and compact cable,and it is highly susceptible to becoming cut or damaged during installationor construction activities. Thus it is necessary to address restoration,backup and survivability.

Wildlife damage to fiber optic cables For instance, There is a plantcalled the Christmas tree plant that treats fiber optic cable as a tree rootand wraps itself around the cable so tightly that the light impulsestraveling down the fiber are choked off.


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COAxial cables

Copper tube with a copper wire running through its center.The copper tube shields electric signals it carries and helpsprevent signals from escaping.

Tube & the wire have the same center axis & hence coaxial.


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Construction and working

Inner conductorsurrounded by a

flexible, tubularinsulating layer,surrounded by atubular conducting

shield.Conduction of

electrical signals bythe cable using aninner conductor


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APPLICATIONS

Transmission line for radio frequency signals.

Video and cable television distribution.

Microwave transmission

Computer connections

Short coaxial cables used to connecthome video equipment.

Common for implementing computer networks,in particular Ethernet.


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ADVANTAGES

The electromagnetic field carrying the signal exists only inthe space between the inner and outer conductors.

This allows coaxial cables to be installed next to metalobjects without the power losses that occur in other types

of transmission lines. Coaxial cable also provides protection of the signal from

external electromagnetic interference.

The advantage of coaxial design is that the electric and

magnetic fields are confined to the dielectric with littleleakage outside the shield.


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DISADVANTAGES

More expensive than twisted pairs.

Very bulky

Has high attenuation so would have the need to implementrepeaters.

Signal leakage: passage of electromagnetic fields throughthe shield of a cable.

Ingress : the passage of an outside signal into the cableand can result in noise and disruption of the desired signal.


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RIBBON CABLES

A ribbon cable (also known as multi-wireplanar cable) is a cable with manyconducting wires running parallel to eachother on the same flat plane.

Thus, wide and flat. Name comes from theresemblance of the cable to a pieceof ribbon.


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ABOUT RIBBON CABLES

Introduction of rainbow ribbon cable by manufacturers foreasier identification of individual conductors in a cable byusage of a repeating pattern of colors borrowed from thestandard resistor color code.

Often known as "hippie cable" due to its distinctappearance.

Usually specified by two numbers:

Spacing

pitch of the conductors,

the number of conductors or ways.

Number of conductors restricted to a few values on thebasis of availability of standard connectors.


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APPLICATIONS

Used in internal peripherals in computers, suchas hard drives, and optical disc drives.

Were used for external connections as well onsome older computer systems (such as the BBCMicro and Apple II series)

Used within a computer chassis to connect diskdrives to the disk drive controllers.


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ADVANTAGES

Extremely small bending radius

High flexibility

Minimum wastage of space

Packeting possibilities

Excellent flexibility as connecting cable in

electronics and in control engineering.


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DISADVANTAGES

Interference of the ribbon-like shapein computer cooling leading to disruption of

airflow within the caseThus, renders the cables awkward to handle.

Almost entirely replaced by round cables forexternal connections and internally as well.

Not flexible.


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TWISTED PAIR CABLES


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TWISTED PAIR CABLES

Shielded Twisted Pair (STP)Unshielded Twisted Pair

Cable, UTP cable is a popularcable used in computer


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Applications of twisted paircables

The same cable provides Audio, Video & Data interface.HDMI is the latest invention which enables video upscalingupto 1080p

Moves are simple with TVs, as simple to computer &

phone.

IPTV (Internet Protocol Television) works on STP.


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PROS

The advantages of these cables are as follows:

It is a thin, flexible cable that is easy to string betweenwalls.

More lines can be run through the same wiring ducts.

Electrical noise going into or coming from the cable can be

prevented.

Cross-talk is minimized.

Less expensive and data transfers are at a high speed.


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SHORTCOMINGS

These cables do have their own shortcomings as well.

Susceptibility to electromagnetic interference greatlydepends on the pair twisting schemes (usually patented bythe manufacturers) staying intact during the installation.

Have stringent requirements for maximum pulling tensionas well as minimum bend radius. This relative fragility of

twisted pair cables makes the installation practices animportant part of ensuring the cables performance.

In video applications that send information across multipleparallel signal wires, twisted pair cabling can introducesignaling delays known as skew which results in subtle

color defects and ghosting.


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CONCLUSION

Thus we have discussed about the varioustypes of cables, their applications, meritsand their demerits.


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THE END

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Elec Cables (1)

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