Instrumentation, Industrial, Automation, Data and Control Transmission Cables
With the evolution of technology intelligent electronic devices such as sensors, inverters, measuring instruments, control and adjustment instruments have developed, which need to communicate with each other for achieving their goal. The idea of network has then become realist not only for computers but also for all devices which have to interact with each other. In order that communication can take place between different devices, it is necessary to refer to a set of rules, defined as communication protocol. Today a variety of communication protocols are used (IEEE 488.2, RS 232,
RS 422, RS 485, PROFIBUS, â€¦..); but the main element for each connection is the cable, which must be designed and produced according to the specifications of the communication protocol and the national, european and international norms.
The main function of the cable is that of transmitting the signal sent by the emitting device to the receiving one as faithfully as possible, then signal losses while it is carried must be reduced to a minimum loss. The main disturbances altering the value of the transmitted signal are the electrostatic and electromagnetic interferences which can be found in any environment. These interferences can be stopped (attenuated) by a suitable shielding of the cable.
The shielding of the cable can be of a tape kind, in order to reduce electrostatic interferences and of a copper braid, in order to reduce electromagnetic interferences.
In both cases shielding not only reduces interferences that the external environment can cause, but it also protects the external environment from possible disturbance caused by the signal propagating inside the cable.
The cable choice should be, therefore, carefully evaluated, considering some fundamental aspects such as type of
laying (for indoors or for moving condition); the characteristics of the installation environment (dry, humid, wet,â€¦); the ambient temperature; the protection from external factors (oil resistance, ultraviolet ray resistance,â€¦); and obviously the electric characteristics linked to the communication protocol.
The cable can be designed and produced for obtaining all of or only some of the following characteristics:
- Optimum mechanical flexibility
- Good resistance to mechanic stress
- Good resistance to hydrocarbons
- Contained dimensions
- Optimum protection of the transmitted signal from external interferences
- Low capacitance
- The necessary insulation degree
- High insulation resistance
The main components of a multicore cable are:
- Separator tape
- Possible shielding
- Possible fillers
The inner conductors consist of copper wires assembled in bunches or in a single bunch of the same diameter (from 0,10 mm to 0,40 mm), the number of wires of the conductor and their diameter distinguish the size which is measured in mm2. They enable the transmission in a low voltage environment.
Core is named the conductor covered with an insulating layer of a suitable thickness. Both the thickness and the material used for insulating depend on the reference norm for the construction of the cable. The single cores can be identified either by their colour or by a progressive number given to each of them, in both cases the reference norms are to be observed ( DIN 47100, CEI â€“UNEL 00722, â€¦ ).
The number of wires, the diameter of the single elementary wire and the pitch characterize the copper braid shielding. The efficiency of shielding is proportional to the coverage percentage of the same, which is the parameter taken under control. It is obvious that a higher coverage implies a lesser flexibility of the cable. This kind of shielding is used to reduce electromagnetic interferences.
The tape shielding is made by wrapping it spiral wise on the cores, thus obtaining an overlap approx. 20% to achieve a total coverage of 100%. This kind of shielding is used to reduce electrostatic interferences.
The sheath is made of a layer of insulating material. It is the protection barrier against certain external factors such as:
- resistance to ultraviolet rays
In order to meet such demands, IMC produces a range of single, paired, triple and multicore cables.
Some cables are produced in pairs, in order to notably reduce the effects of reciprocal influence which are obtained during the signal propagation, the measuring of this characteristic is called â€ścross talkâ€ť.
In this category of shielded cables the cables LiYCY, 2LiYCY, LiYCY-CY, LiYY-CY, Li2YCY-PiMF, Li2YCYv, LiHCH, FR2OH2R (TOP-FLEX), FR2OHH2R, FG7OH2M1 are included.
NOTE IMC CAN SUPPLY ON REQUEST LiYY WITH THE SAME SIZE AND NUMBER OF CONDUCTORS OF LiYCY CABLES, AND ARE USED WHERE THE ELECTROMAGNETIC INTERFERENCE IS VERY SMALL.