Use shielded and unshielded cables correctly

Use shielded and unshielded cables correctly

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The shielded cable and unshielded battles, and which cable provides the best solution for copper structured cabling networks, have long been in the industry. Choose unshielded twisted-pair (UTP) cable and twisted-pair foil Line (FTP) (or U.S. Shielded Twisted Pair (ScTP))

It is not an easy decision to make. In fact, choosing the proper shielding technology from various options and ensuring that these technologies are installed and run is far more important than the choice of FTP or UTP. The conventions are different. In the UK, most European, U.S. and Asian countries usually use UTP cable as the most economical option that is sufficient for most installation requirements. In Germany and other European countries, including France, Switzerland and Austria , FTP dominates.

One of the real problems when installing a system is data integrity. The fundamental goal of a shielded system is to protect the data from potential electromagnetic interference (EMI), such as in industrial facilities and airports and where critical systems are operating, such as military bases and hospitals. A well-designed, properly installed FTP cabling network will undoubtedly improve signal integrity on unshielded systems. However, Molex Premise Networks warns users that in order to work effectively, the shield must be properly grounded. In fact, this is not always possible. Simple to implement. Poorly grounded shielding systems will actually provide worse performance than unshielded systems at the beginning. In the worst case, the shield itself may become a source of radiation, generate a current ground loop, or receive around Radiated, harmful interference to the data cable that leads.

The type of shielding

Shielding is divided into several different types. Two or more strands or four cables can be packaged into one overall shield. In addition, each pair of twisted cables can also be shielded separately. In addition, these individually shielded cables can be It is not possible to cover the second overall shield (called the metal foil pair (PiMF)). Regardless of the design, in order to ensure effectiveness, the shield must be electronically continuous from end to end and properly grounded. When shielding a cabling system, it is also important to choose an overall end-to-end solution. Mixing components that use different systems may lead to impedance mismatches.

Concerns. The cost of shielding the system, including the additional installation work required, is usually 20-30% higher than that of an equivalent UTP solution. Standards and regulations EMI or radio frequency interference (RFI) is the negative impact on the operation of equipment or systems. Any unwanted signal in Europe. In Europe, EMC and its complementary Act 92/31/EEC stipulate radiation and electromagnetic interference immunity requirements. In the United States, the Federal Communications Commission (FCC) Any device manufactured or sold in the United States has a similar regulation.

By measuring the field strength of the generated radiation, the radiation can be determined. The unit is volts/meter and its usual frequency range is from 30kHz to 1000MHz. EMC regulations provide a product family standard for information technology equipment - EN55022, which specifies EMI radiation testing procedures and acceptable limits.

Passed the test, and confirmed that the device can continue to operate effectively in the presence of the corresponding level of EMI, and can determine the anti-interference ability (or sensitivity) of EMI. Currently, there is no family standard for anti-jamming capability testing of IT equipment. Currently it is included in the general standards EN50082-1 ​​(domestic, commercial and lighting industry) and EN50082-2 (industrial environment). These standards and the IEC1000-4 series of basic standards are used to test the anti-interference capability of IT equipment.

It is not clear how the wiring structure fits into this situation. The proposal of the famous DTI-appointed entity for the Molex Enterprise Wiring Network Division in the United Kingdom confirms that the structured cabling was excluded from the provisions of Article 13 of SI 2372: 1992 because of the Large installations cannot be evaluated by EMC

Acceptable. In addition to the provisions of Article 17 of the SI, the wiring system is classified as a passive system and therefore it is not within the scope of the electromagnetic regulations.

The EMC Testing Laboratory of the United Kingdom (EMCTLA) claims that the wiring products “will not cause electromagnetic interference and their performance will not be affected by these interferences.” Therefore, the CE mark is not required to be displayed on the wiring components; in fact, this is illegal.