EuroWire November 2016

News Technology

Measuring devices provide FFT analysis and SRL predictions

Sikora offers a variety of measuring systems for quality control of telephone wires, data cables and coax cables (eg Centerview 8000 for measuring diameter, ovality and concentricity, Capacitance 2000 for capacitance measurement). Regarding the measurement accuracy, the measurement resolution and the measuring rate, all of these devices meet the requirements for providing FFT analysis and SRL predictions. Powerful digital signal processors are by default integrated in the gauge heads. On the basis of the computing power of the gauges, Sikora is able to realise a digital spectrum analyser as well as a prediction of the return loss directly in the gauge head. This means, that the online calculation of the spectrum of cable parameter fluctuations as well as the online prediction of the return loss are executed at the same place where the input data (that is diameter, eccentricity or cable capacitance measuring values) is available with high chronological and amplitude resolution as well as high precision with minimal measuring value noise. A problematic (normally analogue) transmission of high-rate single measuring values is not necessary. For the cable manufacturer the complex installation, configuration and cabling of several single devices is not required. Furthermore, the risk of a distortion of the analysis results caused by the coupling of electromagnetic disturbances is reduced to a minimum, as no broadband data transfer is necessary. Sikora AG – Germany Website : www.sikora.net

The state-of-the-art cable products, eg data cables, requires constant monitoring of the cable diameter, concentricity and/or cable capacitance with regard to smallest, periodically occurring cable parameter fluctuations. These fluctuations may occur from irregularities such as a ‘pumping’ of the extruder, imbalance of rotating parts, periodic fluctuations of the line speed, cyclic fluctuations of the foaming degree and/or periodic fluctuations of the conductor preheating. The most commonly used method for the quality control of data and high-frequency cables is the measurement of the return loss of a certain cable length as a function of the operation frequencies which are supposed to be transmitted on the cable. (SRL) represents the relation – expressed in dB – between a fed signal and the re-reflected signal fraction along the complete cable length towards the entry. While reflections caused by smaller randomly occurring fluctuations may be neglected, reflections caused by periodic re-occurring cable parameter fluctuations should be detected and eliminated. It becomes clear with the following estimation: Caused by irregularities of the production process, periodic re-occurring ‘dents’ are pushed into the cable insulation with a gap of 10cm in between. If a reflection of 0.1 per cent of the fed signal is taken as a basis at each imperfection, a maximal total reflection of 1,000 x 0.1 per cent = 10 per cent can be estimated (neglecting the cable production of The Structural Return Loss

attenuation at 1,000 impurities at a cable length of 100m). This complies with a return loss of 20dB. This value sums up when the signals of all single reflections at the cable entrance are added up in phase. In order to optimise the cable quality as well as to reduce the scrap rate it is essential to search for the root cause of periodic fluctuations on the return loss of the finished cable at an early stage and to eliminate those by adjusting the production parameter. The online prediction of the return loss from short-term cable capacity data offers necessary information. ▲ ▲ At the vertical, 22“ wide-screen monitor of the Ecocontrol 6000, FFT analysis and production data are clearly displayed

Premium quality for cable sheathing

to a stable and higher output of the extruder. Although this compound does not need any cross-linking, it will still meet the stringent requirements for cable applications in environments like wind turbines. These compounds complement the existing range of high grade Mecoline TP compounds. Flexibility at low or high temperatures, oil and fuel resistance (Oil Res I & II according to UL 1277) and improved burning properties are the key properties of Mecoline TP S 1034 F. Flame spread tests according to DIN EN 50399 (CPR) resulted in the rating B2s1d0. The tested cable construction was H05Z1Z1-F (thermoplastic, flexible HFFR insulation acc. to TI6/TI7, medium LOI; no bedding compound). Melos GmbH – Germany Website : www.melos-gmbh.com

Melos has developed new compounds for markets like shipbuilding and wind power in recent years, and has now introduced a thermoplastic, halogen-free compound offering easy processing at higher temperatures of up to 230°C. Other features are high flexibility even at low temperatures, excellent oil- and fuel-resistance, superior fire behaviour and CPR results. Thanks to a strong interaction with customers, Melos and its partners have developed a new flame-retardant, halogen-free, MDH-based sheathing compound. This low-smoke compound is suitable for a wide range of applications. Mecoline S TP 1034 F can be processed easily and provides a wider processing window with greater flexibility. This will lead

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November 2016