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55 Posts in this encyclopedia categoryScattering, capacitive
Capacitive (electrical) coupling occurs between conductors that are at different potentials. Typical sources of interference are, for example: signal cables running in parallel or static discharges. (All information without guarantee)
Screw-in housing
The housing is attached to the mounting surface by screwing it in directly.
Secondary cabling
Secondary cabling is the name of a type of cabling that supplies several floors in a building and the tertiary cabling that connects these individual floors. (All information without guarantee)
Self-extinguishing
Property of a (synthetic) material to extinguish itself when there is no longer a flame on the material. (All data without guarantee)
Semiconductors
Materials whose electrical conductivity depends on various influences: e.g. direction of current, temperature, incidence of light. Insulating materials (PVC) can be modified to be semi-conductive by mixing them with conductive materials (carbon, graphite). (All data without guarantee)
Separating layer
Foils that are applied to the cable core between the individual layers to prevent damaging influences. (All data without guarantee)
SETI harmonisation labelling
Elektriska Inspektoratet (SETI). Finland. Certification body (All information without guarantee)
Sheet metal cut-out
Cut-out in the mounting wall required to attach a connector. (All information without guarantee)
Shielded twisted pair
Symmetrical Category 5 twisted pair cables with twisted and shielded pairs and an overall shield made of aluminium foil or copper mesh to reduce the absorption of interfering noise or radiation. The impedance is 100 Q. (All specifications without guarantee)
Shielded wires
Wires with shield in outer layer, with shield over the cores or in double sheath. The shield can be made of braid, foil or solid metal. In the case of foil, a double wire is used. Labelling "C", with additional PVC sheathing "CY" if copper is used. Aluminium can also be used instead of copper. (All information without guarantee)
Shielding
A sheath made of highly conductive material over a single core, a group or all cores of a wire. Shields are used to protect wires from interference from external electrical and/or magnetic fields. Or to prevent the wires themselves from interfering with the environment. Shielding options: via cable braiding or by spinning with copper wires, as a foil winding made of copper or aluminium or via closed, tubular bodies made of copper or aluminium. For shielding, the coverage density is defined as a percentage of the shielded area. (All data without guarantee)
Shielding attenuation
EMC properties of cables and connectors: The shielding attenuation is a measured variable that measures the effectiveness of a shield. The shield has the function of protecting a room against an external electrical field, a magnetic field or an electromagnetic field. Its effectiveness is measured with the shielding attenuation. Shielding attenuation is also specified for shielded wires. The usual, technically unambiguous measured variable for recording the shielding effect of a wire is the transfer impedance, formerly known as the coupling resistance. (All data without guarantee)
Shim wire
In most cases, the filler wire is a tinned copper wire that should be in contact with the aluminium layer of the shield over the entire length of the wires or cable. It must lie very loosely (corrugated) on the cable core so that it does not break off when the wires are bent. The drain wire should bridge any shield breaks. (All information without guarantee)
Short-circuit current
The short-circuit current is a current that begins to flow between two conductors due to a fault. (All data without guarantee)
Short-circuit proof
Equipment such as cables, wires and devices are considered short-circuit proof if they can withstand the mechanical (dynamic) and thermal effects of the expected short-circuit current without their functionality being impaired. (All data without guarantee)
Signal propagation speed (NVP)
Signals propagate in all wires at a speed that is always less than the speed of light. The NVP value indicates the ratio to the propagation speed of light. (All data without guarantee)
Silicone rubber
Silicone rubber as a jacket compound is used for continuous temperatures of 180 °C and short-term temperatures of up to 250 °C, for example. It also has good dielectric properties and can be cross-linked. (All data without guarantee)
Single wire
Starting product for all other wire products. It is bare, i.e. without an insulating layer. (All data without guarantee)
Skin effect
The higher the frequency of the useful or interference signal, the more the high-frequency current is pushed to the surface. The skin effect is the property of an alternating or high-frequency current in a conductor to push field lines to the surface through induction processes. This limits the penetration depth of an electromagnetic field radiated from outside into the object and thus also its effectiveness inside. (All information without guarantee)
Slide
Plastic films, metal foils and metal-laminated plastic films are used for a wide variety of purposes. The plastic film has mechanical protective functions, e.g. as padding under a shielding braid or to protect underlying wires from being cut during stripping. Metal foils are used for electrical shielding. (All information without guarantee)
Smallest currents
Contacts in connectors with a silver surface are very conductive. A black oxide layer forms over the service life due to the affinity of silver to sulphur. This thin, soft layer is easily broken through when the contacts are plugged in, so that low contact resistances are guaranteed. With extremely low currents and low voltages, however, signal distortion can occur. Where such an effect leads to malfunctions and under extremely rough and aggressive operating conditions, contacts with a gold surface are recommended. (All data without guarantee)
Smoke density
The smoke density is measured on halogen-free wires and cables in accordance with VDE 0472 T 816, which also complies with the IEC 1034-1 regulation. (All data without guarantee)
Solid ladder
Conductor which, in contrast to stranded wire, consists of only one wire. A rigid wire is suitable for fixed installation. (All information without guarantee)
Spiral cable
Flexible wires that are formed into a spiral spring. The wires are wound onto a mandrel. By applying heat (tempering), the stresses in the plastic caused by the winding process are relieved, so that after cooling, the spiral shape remains as a stress-free state of the wire. When stretched, the spiral lengthens and returns to its original state when the force is no longer applied.
Stabiliser
a) A component used in some plastics to maintain physical and chemical properties during processing and service life. b) Additives (e.g. lead, tin or cadmium salts) for plastics. They delay or counteract the degradation and ageing process that occurs under thermal stress. (All information without guarantee)
Standard cables and wires
Standard wires and cables are products of the cable industry that are manufactured and tested in accordance with the norms and standards of German, European or global standardisation institutes.
Standards
In order to standardise the design and testing of all products manufactured in the cable industry, "standards for wires" with their abbreviations were created almost 100 years ago (1907), which even then described the wires and cables in a reproducible manner. Today, almost all wires, cables and accessories in Germany are manufactured in accordance with VDE, CENELEC and IEC standards. (All information without guarantee)
Standing alternating voltage
The AC withstand voltage is an overvoltage in the form of alternating voltage (50/60 Hz). It is applied for one minute during the dielectric strength test. (All data without guarantee)
Star quad
A star quad is created by stranding four insulated cores together so that the four core centres lie on the corners of a square. The two speech circles are formed from two diagonally opposite cores. The individual cores are colour-coded or bar-coded. (All information without guarantee)
STP
In twisted-pair wires with foil shielding of the individual pairs and overall braided shield (STP = Individually Screened Foil and Braid Twisted Pair), the cores are twisted in pairs and individually shielded with a metallic foil to achieve particularly low near-end crosstalk. An overall shield is also used. (All data without guarantee)
Stranded wire
Stranded wires are intended for fixed wiring in measurement, control and communication technology devices. They are used for frequent bending, shocks or vibrations.
Stranded wire
In electrical engineering, stranded wire is an electrical conductor consisting of thin individual wires and is therefore easy to bend. Copper is predominantly used as a conductor in electrical cables. In technical terms, electrotechnical standards (e.g. IEC 60228 / VDE 0295) refer to these strands as "fine or very fine stranded conductors" to differentiate them from inflexible solid or stranded cores.Thinly insulated strands are also known as antenna strands. In high-frequency stranded wires (HF stranded wire), the individual wires are insulated from each other by a layer of varnish, even though they have the same potential. This allows the influence of the skin effect to be reduced or avoided in high-frequency technology - otherwise only a small part of the total cross-section would participate in the current transport. A desoldering braid is a braid of stranded wire pieces for the clean thermal release of soldered connections (absorption of the liquid solder by capillary action). (All information without guarantee)
Stranding bond (stranding bond)
If several wires were laid parallel to each other without stranding, this structure would be deformed when bent. The inner wires would be compressed and the outer wires would be overstretched. To keep the conductors flexible and movable, the individual wires must be twisted together in a helical shape. The result is a stranded bond or stranded bond. (All information without guarantee)
Strength
The strength is the maximum stress that a material can be subjected to in a given cross-section. It characterises the resistance behaviour of a material to deformation. The strength is defined on the basis of a maximum force at a certain elongation or a certain flow behaviour on the undeformed cross-sectional area of the material. Strengths are not the actual stresses that occur, but are usually calculated from the nominal stresses, i.e. from the test force and the cross-sections before the test begins. Depending on the type of stress, different strengths are defined, e.g: Tensile strength, compressive strength, compressive strength, buckling strength, torsional strength, shear strength. (All data without guarantee)
Stripping length
Length of the stripped stranded wire or wire end. Conductors for connectors must be stripped to a certain length before assembly. If the conductor is stripped too short or too long, the overvoltage behaviour of the connector changes and no longer meets the specifications. Correct stripping is a prerequisite for: compliance with the maximum contact resistances, correct latching of contacts in the insulator, ensuring the current carrying capacity. Axial screws may also only be tightened to a specified torque in order to maintain conductor pull-out forces and contact resistances. So that the conductor is not destroyed. (All information without guarantee)
Supporting organ
Ropes made of hemp, steel or plastic are installed in the construction as a load-bearing or tensile force-absorbing element. In most cases, the supporting element is arranged towards the core, i.e. in the centre of the cables and wires. However, there are also constructions in which one or two steel cables are arranged outside the core bundle but under a common outer sheath. (All information without guarantee)
Surge current
The surge current is the inrush current that may flow briefly via the output. (All data without guarantee)
Surge current carrying capacity
A surge current load on the contacts can be caused by switching operations but also by short circuits. The briefly very high power loss cannot be dissipated to the outside and leads to localised heating of the contacts. Different current carrying capacities result depending on the design and shape of the contacts. (All data without guarantee)
Switch wire
The switching wire is an installation wire for wiring in control, measurement, communication and transmission technology devices.
Switch-off behaviour
The shortest cable route should always be selected for installation. Cable runs that are too long limit the required tripping current in the event of a fault. This can delay or prevent switching off. The maximum cable length that can be used between the power supply and the end device depends on the following criteria: Maximum current of the power supply, internal resistance of the circuit breaker, line resistance. The cable resistance depends on the cable length and the conductor cross-section. (All data without guarantee)
Switching cable
The switching cable is used to establish connections between and within devices in measurement and control technology, control technology, communication and transmission technology, and the installation of carrier frequency and PCM systems.
Switching discharges
Switching operations are referred to by the abbreviation SEMP. This term stands for Switching Electromagnetic Pulse. In this context, switching operations refer to the switching of powerful machines or short circuits in the power supply network. During such processes, very high current changes occur in the affected wires within a few fractions of a second. (All information without guarantee)