Certifying infrastructure cabling in compliance with standards is a time-consuming business. A cabling certifier, such as the WireXpert 4500 from Softing IT Networks, is used to check the extent to which the relevant specified standards for evaluating performance are met for different cabling systems. In addition, the accuracy of the devices is constantly evolving, which at the same time requires appropriate data management software, such as eXport from Softing IT Networks, in order to have the measured data quickly available. However, this software should also include the possibility to correct possible setting errors that occurred at the beginning of the measurements.
Nothing is more annoying than when it is discovered after the measurement has been completed that incorrect settings have been made on the device. For example, when measuring copper networks, rating standards and the NVP value (shortening factor or length factor of the installed data cable) are often set up incorrectly. If, for example, the system was tested at too low a power class, the hours of measurement will have been in vain.
This is where eXport comes into play. Because with the help of this software, measurements with incorrect basic settings can be corrected. In this so-called re-certification, the correct measurement standards are subsequently superimposed on the measurement data and the newly selected limit values are simply applied to the distances already measured. Since the measured values remain unchanged, the data integrity remains unaffected - as does the date of the measurement. This correction of incorrect specifications is also possible for the NVP (Nominal Velocity of Propagation) value.
The NVP value is often critical
If the measurement technician now wants to certify category 7 or 7A cabling, for example, the NVP value should be between 0.78 and 0.82. This means that the transmission speed of the test signal sent by the certification device is between 78 and 82 percent of the speed of light (300,000 km/s) on this type of cable. A reflection measurement is used to determine the lengths of the cabling sections. If, for example, a value that is too small is multiplied by the length formula (propagation time of the signal divided by two), the calculated lengths of the section are too small. Technicians often use values that are too high in order to gain a small advantage when calculating the length via the measurement protocol. However, the deception is usually discovered when the measured values are compared with the data sheet, in which the correct NVP values are noted.
Overall, it must be said that the incorrect specification of the NVP value, whether intentional or not, is often critical. Especially here, eXport gives you the chance to correct the value afterwards. With this re-certification, the measurement does not have to be performed again. The integrity of the data remains guaranteed because the runtime measurement is preserved and only the factor in the calculation formula for the length is changed.
What works? What does not work?
Classical setting errors in the context of a certification are also the testing against wrong performance classes. It happens, for example, that testing is performed for class E instead of class EA, which means that no statements can be made about the use of the cabling for 10 Gigabit Ethernet, but only for up to 5 Gigabit Ethernet. Or topologies are misinterpreted: For example, a measurement standard is used for a 3-connector link that has softer limits than the corresponding standard for a 2-connector link that would actually have been built. It is particularly embarrassing when the device is set to the American standard, which divides the total distance into "categories" and not into power classes as we do. Critical inquiries from the customer are inevitable here.
Nevertheless, these errors occur again and again, and so in the past, as a consequence, new measurements with corrected settings had to be carried out in most cases. But thanks to the data management software eXport, this can now be corrected with little effort. Thus, through the already mentioned re-certification, the correct measurement standards can be placed over the recorded measurement values. In order to make re-certification possible at all, it is therefore necessary to carry out the measurements in the smaller classes beyond the nominal frequency and to store them in the background. For example, the certifier WireXpert stores measurement data for the power classes up to EA to 600 MHz in order to be able to recertify "upwards". For the higher performance classes, measured values up to 2,500 MHz are even documented in the background. Re-certification is also practical when it is necessary to find out whether older systems also support faster transmission rates and applications.
However, re-certification cannot be applied if measurement data must be changed. For example, it is not possible to change the measurement of a transmission link (channel link) to a cabling link (permanent link) and thus damage the integrity of the measurement data. Systems that allow such a thing are on the edge of legality. Also the exchange of components of the cabling link make old measurements invalid.
Whereas it used to be the exclusive task of the software for cabling certifiers to manage and evaluate the measurement data, today data management software such as eXport is intended to support the measurement engineer in his work. Therefore, for example, the mentioned setting errors on the device can be corrected afterwards or installations can be certified to new transmission standards as long as the collected measurement data still reflect the real cabling of the installation. In the future, this will allow installation companies to save time and resources during measurements and to correct possible errors on the PC without much effort.