Choosing the wrong cable to connect to a system or to equipment can cause a network or communication failure

so it’s important to know what to look for before deciding on a cable. Mistakes can be costly if many metres of cabling are involved. It’s not just the cost of the cable: it’s also the cost of removing reinstalling the cable runs. So use this checklist to help you choose the right cable.

1. Environment

Office environments are clean and quiet, and cables are often further protected by ducting. However, in industry, many cables are connected to devices that are being used in more demanding conditions. For example, instrumentation systems and control applications may be used at sea or in mines, refineries and factories. The amount of vibration that the cable must resist will affect the type of cable used, as will the temperature in the environment.

2. Data Transmission Rates

The “Cat” ratings on Ethernet cables refer to the data transmission rates which the cable can handle. Cat 5e cables can deal with up to 1 GB; CAT 7 can handle up to 10 GB.

3. Cable Jackets

You need to consider whether the cable jacket will be exposed to oil, abrasion or flexing. PVC is cheap and suitable for general use, but if there is a fire risk, Flame Retardant No Chlorine (FRNC) cable is a must. Even if it burns, this cable doesn’t give out a lot of smoke. Thermoplastic elastomer (TPE) is good at resisting temperature extremes, flexes easily and will resist coolants and oils. And polyurethane cables (PUR) remain flexible through a wide temperature range and are very resistant to wear and tear. PUR is used widely in robotics, heavy industry, transport and for control and sensor cables.

If you’re not sure which type you need, take advice from a reputable cable supplier, with expertise across the range of cables such as www.cableintelligence.co.uk.

4. Unshielded or Shielded?

If there is a lot of “noise” in the environment that could interfere with the information being transmitted down the cable, a shielded cable is necessary to make sure the data reaches its destination without corruption or dropping out.

5. Twisted or Bonded Pair

Bonded pair cables are manufactured so that no gaps appear in the insulation of the two cables inside. This can keep the cable in better condition when it is being installed. Twisted pair cables can “gap” while they are being installed and can also develop mismatched impedance.

6. Voltage

All cable is tested and declared suitable up to a specific voltage. You must ensure that the cable is capable of carrying the load that is produced by the system. The cable voltage must be higher than the system voltage.

7. Coaxial Cable

This cable is excellent at resisting interference from other signals. It can also carry signals for a longer distance between devices on the network than twisted pair, for example.

8. Fibre-Optic Cable

Fibre optic doesn’t have any interference problems because its glass core transmits light – not signals. Resistant to moisture, it’s often used for cable runs between buildings. It carries much greater amounts of information but it can be difficult to install.

There are two kinds of fibre-optic cables – tight buffered and loose tube. Each type of cable contains a strengthening agent such as strands of stainless steel wire or sleeves that are filled with gel.

Loose tube fibre-optic cables are intended for use in more challenging environments, such as outdoors. The inner fibre core is protected by cladding and coatings that enclose the fibres in a protective tube which is fairly rigid. The ones with gel sleeves can be used in environments where humidity is high or there are condensation problems.

Tight buffered cables usually have a two-layer coating, the first of which is plastic and the second a waterproof material. These cables are best suited for applications inside, and although they are more robust than the loose tube cables, they tend to suit only moderately long cable runs. Loose tube cables often require a kit called a “fan out kit” if they require termination or splicing.

9. Fibre-Optic Patch Cords

These are fibre-optic cables that have a connector at each end to allow the cable to link to optical switches or to two pieces of telecommunication equipment. The patch cables are not used outside. The simplex type have a single fibre and a single connector at each end. The duplex ones have two fibres and each end has two connectors.

10. Fibre “Pigtails”

A fibre “pigtail” cable has a single fibre and an optical connector at one end, while at the other end there is some exposed cable which is stripped. This end is fusion-spliced to a single fibre of a multi-fibre cable.