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News
Technology
November 2016
44
www.read-eurowire.comThe
production
of
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.
The
Structural
Return
Loss
(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
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.
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.netMelos 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
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.comMeasuring devices provide FFT analysis and
SRL predictions
▲
▲
At the vertical, 22“ wide-screen monitor of the
Ecocontrol 6000, FFT analysis and production data
are clearly displayed
Premium quality for cable sheathing