Calibration is needed in case changing paramenters such as different material properties, fluctuating temperatures or other environmental conditions would affect the measured values. Additional affects reducing the accuracy of a system can be seen by wear or tear of moving mechanical components such as optics or moving assemblies. SIKORA's range of measuring products is not only designed to withstand industrial environments - it is designed to keep the precision from the day of delivery for many years of heavy duty. For example, a major benefit of the X-RAY 2000 is that it is constructed without any moving parts. The immediate calculation of the data directly from the X-ray picture without the need of transmission from one end of the line to another ensures steady values and calibration-free measurement precision.
[Charged Coupled Device]
A technology most widely used in modern digital cameras. Most SIKORA devices like the X-RAY 2000 and LASER 2000 series are making use of CCD line sensors in combination with pulse-driven laser diodes, which, in combination with the integrated Diffraction Analysis, enables for highest measuring rates and precise measurement values even if the product is oscillating in the measuring area. Moreover, lack of moving or wearing parts ensures lowest maintenance effort and eliminates any need for calibration.
[Capacity/Diameter-Control]
During the production of communication cables, it is interesting to control both the outer diameter and the capacitance of the product online in order to ensure the quality of the final product. It is well known that these two parameters are coupled physically. A change in the process will cause a change both in the capacitance and the outer diameter of the cable at the same time, however in an opposite direction. If the outer diameter increases, the capacitance falls and vice versa. It is proved that such a system cannot be controlled well in a traditional feedback way. In the past years, some control methods have been developed that switch between controlling the outer diameter respectively the capacitance, but the result is so far unsatisfying.
SIKORA's most innovative approach is based on an elegant solution of decoupling the interaction between the change of the capacitance and the change of the outer diameter in a way that these two parameters can be controlled simultaneously without mutual influences. The control loop becomes much faster and more stable without oscillation.
The cloud diagram is a special display format of the online measurement of the CENTERVIEW 8000, an innovative eccentricity, ovality and diameter measuring device, on the processor system ECOCONTROL 2000. The display of the single eccentricity measuring values in the form of points on the display creates a cloud diagram whose density complies with the frequency of the distribution of the single values.
If the frequency of the single eccentricity values is focussed in the middle of the circle presentation, then the conductor is concentric. However, if the single eccentricity values accumulate at the border area of the conductor, then there is an eccentricity. In the standard deviation this would be highlighted in color.
The cloud diagram especially reveals apparent concentricity, due to quick eccentricity variations or averaging's. A special form of quick eccentricity variations occurs for example if a conductor oscillates in a circle line before the intake into the extruder around its center-line. Such an oscillation produces an eccentricity depending on the oscillating amplitude. Although, a permanent eccentricity exists, the common display would not show eccentricity due to average determination. With the newly developed concept of the cloud diagram these quick oscillating eccentricities are visualized.
Non-contact opto-electronic measuring techniques are increasingly employed for the automation of measuring and test processes in industrial manufacturing. For a most accurate dimensional measurement of work pieces, the shadow projection method has gained widespread application in production metrology. If the shadow projection principle is extended by utilizing diffraction phenomena, the dimensions of work pieces can be determined with accuracies well below the spatial resolution of the light sensor that captures the shadow image. The object to measure (wire, cable or other elongated product with nearly circular cross-section) is illuminated by the coherent monochromatic light emitted by a pulse-driven laser diode. The resulting shadow is registered at a CCD line sensor. The gauge is a dual-axis system, i.e. has two orthogonal measuring axes. Using a highperformance digital signal processor, the data processing for analysing the diffraction patterns and calculating the diameter values (one per axis) is done completely inside the measuring head. Limited by the read-out times of the CCD line sensors, up to 500 measurements per second are achieved. The measuring system is equipped with various interfaces for communicating the diameter readings to display units or a process control computer.
[Fast Fourier Transformation]
At the cable production, particularly at the manufacture of communication cables, smallest cable parameter variations should be avoided in case they occur periodically. The manufacture of state-of-the-art cable products demands a permanent control of the cable diameter, eccentricity and/or the cable capacity regarding periodical variations. The online analysis of these measuring data in the frequency range represents a powerful controlling tool for the determination of periodically occurring irregularities at the cable extrusion.
Periodical variations of cable parameters can be caused by irregularities such as pumping of the extruder, unbalance of rotating parts, periodical variations of the line speed, cyclical change of the foaming level and/or periodical irregularities at the pre-heating of the conductor.
While the existence of periodical variations can only be taken with difficulties from the chronological sequence of the measured cable parameters, with the analysis of the measuring values in the frequency range, periodically recurrent variations can be realized at an early stage. Moreover, the calculated frequency spectrum offers helpful information for identification of the causes of cyclical irregularities in the cable production process, especially, when product parameters, such as the line speed, are changed.
Powerful digital signal processors are included in all measuring heads of the INLINE series. Due to the integrated computing power, a digital spectrum analyser is realized directly within the gauge head. Furthermore, in addition, a prediction of SRL (see Structural Return Loss) is implemented. That is to say, that the online calculation of the spectrum of cable parameter variations as well as the online prediction of the SRL is shown where input data, i.e. diameter, eccentricity or cable capacity measuring values, are available with high amplitude resolution and high precision at minimum measuring value noise. A problematic (normally analog) transmission of highly rated single measuring values is not necessary.
[Mean Time Between Failures]
All measuring devices from SIKORA stand out because of the nearly unlimited operation time, but also because of the innovative measurement principle without moving parts which avoids maintenance. The Mean Time Between Failures (MTBF) - the statistic, average time, after which a device of this series shows a repairable defect - reflects this long life expectancy. The MTBF for example of a device of the LASER 2000 series amounts 15 years.
The SIKORA "Multizone Electrode" capacitance gauge provides two measurements that satisfy important aspects of the production. The system provides the highest precision measurements while at the same time one can monitor for the short periodical variations that are the source of coaxial capacitance attenuation (see FFT analysis and/or SRL Prediction). Technically we must keep in mind the fact that the measured capacitance value is an average of individual measurements over the cable length within the measuring tube. For precise measurements this tube must be as long as possible, however for structural return loss analysis a short electrode provides benefits of being able to see the short periodic variations which provide us the best window of analysis at the highest operational frequencies. SIKORA has solved this requirement for two measuring techniques by implementing both a long and a short electrode into a combined measuring tube. This patented* arrangement provides both the highest precision and SRL prediction up to 8 GHz. The combination system offers two solutions in one, providing the combined solution where ones alternative is to purchase two individual systems to provide the same information.
More than 30 years ago, contact measurement was used for the measurement of the diameter and eccentricity of wires and cables.
This technology was based on a mechanical measuring system with integrated guide rollers that centred the measuring object to the position of the measuring device. As the wire or cable was mounted on wheels this method often led to damages of the product surface. The consequence was periodical faults as well as an additional attenuation of the transferred signals during data transfer. Further collateral effects like abrasion of the cable surface as well as the low level of automation challenged the use of these devices.
The demand for more reliable and robust measuring procedures resulted in the development of innovative non-contact measuring devices. These do not have any guide rollers, and center automatically. Contact and damage of the product are therefore eliminated. Due to its higher measuring precision and wear resistance non-contact measuring systems have quickly replaced contact measurement and are an important component of production lines in the wire and cable sector.
Since the foundation of the company in 1973 SIKORA has exclusively produced non-contact measuring devices at its headquarters in Bremen. These innovative measuring systems guarantee highest precision as well as ultimate reliability and productivity.
[Return On Investment]
ROI [relating to a single investment] is a ratio to evaluate an investment under consideration of the money gained (savings, profit) which is expected from that investment within the service life.
It can be expressed as:
ROI = (Savings / Investment) * 100%
In most cases, a SIKORA measurement system amortizes within less than 6 months, equal to a Return On Investment of more than 200% in one year.
Impurities in the PE (material) melt due to premature (chemical) crosslinking in the extrusion process. Scorch not only influences the extruder lifetime but the general quality and durability of the finished product as well, which may lead to defects and rejections.
[Surface Mounted Device]
All SIKORA devices base on SMD technology, which enables not only for smaller, lighter devices, but for an enhanced feature set like our powerful FFT analysis, which thanks to SMD design can be calculated directly in the measuring head. Because of a compact and robust design, all SIKORA measuring gauges are well-suited for rough production environments.
[Structural Return Loss]
Structural Return Loss (SRL) means that at the transmission of signals of a conductor, for specified transfer rates respectively transfer frequencies, losses occur due to reflections. The attenuation of the signal amplitudes through reflection is defined as Structural Return Loss. The Structural Return Loss within the transmission range should generally not be higher than 5 % for a manufactured conductor.
For the quality control of data and high-frequency cables SIKORA measures the SRL of a cable length as a function of the operating signal frequencies, which are later to be transferred to the cable. The Structural Return Loss represents the relation between the provided signal and the reverse reflected signal parts along the full cable length to the input.
In order to optimize the cable quality as well as to reduce scrap it desirable to detect impacts of periodic irregularities on the later SRL of the manufactured cable at an early stage.
The online prediction of SRL from short-term cable capacity data provides appropriate information. This prediction method is based, especially with regard to online demands on the Fourier-Transformation according to the FFT-Algorithm.
