EuroWire January 2016

Technical article

should be positioned at the same level as the inductive sensors. In this positioning, the optical paths are shaded by the inductive sensors. For that reason, the optical measuring planes are divided. One optical measuring plane is arranged before and one after the inductive sensor plane. As a consequence, only an absolute straight and horizontal conductor can generate accurate measuring results. In practice, however, slightly angled positions or bends in the conductor typically have to be expected. This means that the measuring device has to be able to record precise measuring values even under these conditions. Picture 6 shows a cable running in reference to a straight line. The cable, however, is running in an inclined position to the actual intended production line. In the illustration, the inclined position of the cable is exaggerated for a better understanding. A straight or inclined line, in this case a straight conductor, is defined by two points. By means of the first and second optical measuring device, the sloping positions of the cable will be identified and its influence on the measuring results will be determined and fully compensated. Determination and compensation of a sag or bend of the cable Picture 7 illustrates a cable that shows a sag or bend. For a better understanding, the illustration of the bend of the cable is extremely exaggerated and, in practice, not likely. The bend of a conductor can be described by a circle, whose position and curve radius is defined by three points. With this information, the processor system is able to calculate the exact position of the cable in the inductive measuring plane and to fully compensate for the influence of angled position and/or bends. As shown in the picture, the measuring system is built in a way that the position of the cable is measured at four points, shown in the illustration as P1, P2, P3 and P4. Due to this, the measuring system is able to detect even irregular deformations of the conductor. Measurement of a sloping position of the cable

▲ ▲ Picture 2 : Standard presentation of eccentricity

▲ ▲ Picture 3 : Random type distribution of the single values of the eccentricity

(oscillating) conductor prior to the extruder crosshead. Picture 5 shows an ellipse type distribution of the scatter plot, which can happen, for example, when the conductor is oscillating or vibrating in one direction directly before entering the crosshead and which therefore additionally causes eccentricity variations. ▲ ▲ Picture 4 : Ring type distribution of the single values of the eccentricity

This permanent rotation eccentricity would also not be visible with a standard presentation of eccentricity (as shown in Picture 2 ). In order to ensure a high measuring accuracy of the conductor within the insulation, the optical measurement axes ▲ ▲ Picture 5 : Ellipse type distribution of the single values of the eccentricity

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January 2016