Instrumentation Cables rated at 300 volts have copper conductors #22 AWG to #14 AWG, while those rated at 600 volts have #18 AWG to #10 AWG, and unarmoured and armoured types are available. The cables may be an assembly of single conductors, pairs, triads or quads. The conductors are stranded seven-wire tinned or bare copper. The insulation is usually a PVC compound chosen dependant on the environment for which it is intended.

Insulated conductors are paired with staggered lays to prevent electromagnetic coupling and crosstalk. When individual shielding is specified, each pair is aluminum/polyester shielded with drain wire to eliminate electrostatic interference.

Armoured cables have an interlocked aluminum or galvanized steel armour (Figure 10). The armouring is applied over an inner PVC jacket, followed by a PVC outer jacket. Armoured cables are suitable for installation on cable trays in dry, damp and wet locations, or direct earth burial.

Unarmoured Instrumentation Cables are intended for installation in raceways/conduit (except cable trays) in dry, damp or wet locations, or direct earth buried. Unarmoured Cable with Type TC (Tray Cable) designation, may be installed in cable trays.


Thermocouple Extension Cables

Thermocouple Extension Cables (Figure 9) have a 300 volt rating, and are of similar construction to Instrumentation Cables, but the metals/alloys used for the conductors are different. Thermocouples measure temperature using the electric current created when heat is applied to two dissimilar metals/alloys. The cable assembles may consist of as many as 50 pairs, depending on the number of locations being temperature monitored.