What is the cable made of?.
Technical security equipment has become an integral part of our lives. We are filmed by video cameras on buildings, access to parking lots is limited by barriers, in office premises we are surrounded by security and fire sensors, and when we come home, we deal with an intercom. All these wonderful devices perform a lot of necessary functions, but most of them require cables to transmit information and power.
Therefore, it is obvious that the reliable operation of security systems, and ultimately our safety, largely depends on the quality of the low-current signal cable.
What do you need to know to be sure of the quality of the cable? What does it consist of? How can you be sure that the material the cores are made of is really the one declared by the manufacturer and/or seller?
A standard low-current signal cable usually consists of an outer sealed sheath (in our case, most often made of PVC, but can also be made of polyethylene) and 2 to 30 PVC-insulated cores enclosed in it. Each core is one (in a single-wire signal cable) or several conductors, usually 7 or more (in a multi-wire signal cable). In this article, we will consider the widely used multi-wire signal cable, since the single-wire version of the signal cable is very limited in application due to the high probability of breaks during operational bends.
Conductor resistance is the main criterion for the quality of a multi-wire signal cable. When calculating conductor resistance, the most important parameters are the conductive material (e.g. copper, tinned copper, copper-plated aluminum, copper-plated steel, etc.) and the cross-section of the conductor.
Copper has better conductivity than other metals. Aluminum, steel, and their alloys are significantly cheaper than copper, but they have worse conductivity and higher resistance, which affects the quality of signal transmission. This is why copper is an ideal material for cable. It has lower resistance than copper-plated aluminum or steel.
The higher the resistance, the greater the voltage drop along the cable. This affects the efficiency and reliability of the system: sirens may not turn on when the alarm is triggered or turn off unintentionally, sensors and control panels will not always perform their functions correctly, which will ultimately lead to frequent false alarms or system failure.
The best low-current signal cable is one whose cores are made of 100% tinned and tempered copper conductors. Tinning is very important because it improves termination and sealing of the core and helps to avoid oxidation, which is common with copper conductors. Although tinning gives the cable additional resistance (see comparison table), which slightly affects the final conductivity, its use has many more advantages than disadvantages. Tempering gives copper greater flexibility and plasticity. Cables whose cores contain aluminum conductors are less flexible, since aluminum is harder and has lower tensile strength, which leads to the fact that cores made of aluminum conductors are more prone to breakage.
Another advantage is that copper has an advantage over aluminum in terms of resistance to heat.
The comparison results of different types of signal cables can be seen in the comparison table. The manufacturers who agreed to take part in this small study are listed in the table under their own brands.
And finally, practical advice for installers of technical security equipment. How to determine what a cable is made of: copper, tinned copper, steel or aluminum? The answer is simple: by color.
A copper cable has the same reddish-orange color on the cross-section of the core and on its outer surface, which is inherent in pure copper. A uniform grayish-steel color on the cut and on the outer surface is, at best, either copper-plated aluminum or copper-plated steel, and at worst, pure aluminum or steel. The highest quality signal cable, made of tinned copper, will have the color of pure copper on the cut and a grayish-steel color on the outer surface, which is imparted by tinning.