Recently, Fluke summed up the lack of cable knowledge to identify cable shoddy. First of all, the wire diameter is fine, and the work is cut. Wire diameter is the most common method of falsification. For example, the standard requires the use of wire gauge No. 23 (AWG23), and the cable printed mark is also AWG23, but the wire gauge No. 26 (AWG26, finer wire diameter) is actually used. If you don't have a vernier caliper in your hand, it doesn't matter, you can test the resistance value to help determine. The tapered copper loop resistance value is larger than the normal diameter copper cable. The loop resistance test results can be given in seconds using the Fluke DTX or DSX Series cable tester. Another consequence of the thinner wire diameter is the large loss, which leads to insufficient signal transmission distance or weak signal strength. The DTX/DSX cable tester can directly give the loss value (attenuation value). An unqualified cable will give an alarm. The 100-meter sample can be cut according to the standard (instrument built-in standard), or the whole box line (305 meters) can be used for testing (DSX series). According to experience, the data cable is often the hardest hit area, the communication bus (twisted pair), and the control bus are slightly better.
Secondly, the interference between the pairs is too large and the processing is not in place. The data cable and part of the bus are composed of multiple pairs of twisted pairs (4 pairs, 2 pairs). If the twisted pair has a low twist ratio (which can save material), the electromagnetic radiation crosstalk between the pairs is relatively large, and the pair interferes with each other when transmitting data, resulting in an increase in the packet loss rate when the signal data is transmitted at a high speed, and the data transmission is intermittent. Sometimes there is no fault, sometimes the production line is inexplicably interrupted, and even when the communication is completely interrupted. However, data transmission at low speed may not find such a problem of cutting corners. The crosstalk parameter (NEXT) is found to be unacceptable through the DTX/DSX test.
Furthermore, the wire pairs are not uniform in manufacturing and the manufacturing precision is too low. Low manufacturing precision results in uneven cable structure and large signal reflection (echo), which can interfere with twisted pairs and buses that are used for both signal transmission and signal reception. The DTX/DSX test results show "Failed". In addition, uneven manufacturing can also cause the signal cable to be resistant to external interference, and sometimes there is no erratic failure phenomenon. The DSX can detect whether its anti-interference indicator (TCL/TCTL/unbalanced resistance, etc.) is up to standard.
In addition, the installation is rude and the link is not available. Sometimes, although Party A has purchased high-quality products with a high budget, the actual use effect is not satisfactory. Indicators such as error rate and frame loss rate are not good or unstable. This has a lot to do with the construction level of Party B. The construction level of the construction team from the guerrillas on the road is usually not guaranteed. After all, communication lines, signal lines, control lines, etc. are more professional in terms of the fineness of installation. For example, if the twisted pair is too long, it will cause crosstalk between the pairs to increase; the joint is too deformed or excessively kinked, and the binding is too tight and too tight, which will cause excessive echo interference; the cable bundle is too large (for example, more than 48) The bundle of the roots will also cause excessive interference between the cables. These can lead to problems such as increased error rates, good times and bad times, and unstable communication and data transmission. In the case of a broken or lost key command frame of the subway signal transmission, it may cause a disaster of control error, causing a major traffic accident. Let DTX/DSX detect the installed link, and problems such as unqualified parameters caused by these improper operations will be exposed. And DTX / DSX can directly locate the fault location, such as reporting 23.7 meters of crosstalk or echo parameters failed within 15 seconds.
Or the fault is frequent and the warranty is not in place. Using poor cable construction, although various applications can operate normally at the time, but due to the unqualified link left to the system the margin is too low, when encountering cable aging, vibration and wear, high temperature and high humidity, air pollution (sulphur dioxide, etc. Oxidation/blackening of the copper contacts, deterioration of the electromagnetic environment, etc., will gradually appear flashing or a variety of inexplicable problems, making maintenance personnel a big headache. The DTX/DSX provides unqualified link detection reports to the acceptance maintenance personnel and indicates the approximate cause and physical location of the failure. With the implementation of the regular inspection and visual inspection system, the communication reliability of the cable link can be maintained at a sustainable high reliability level.
The difference between the selection and the actual supply is also a big problem. During the design and bidding phase, Party A may request Party B and the supplier to conduct the selection test. However, it was discovered afterwards that there was a significant quality difference between the samples provided during the selection and the products actually supplied. Therefore, the better way is to insist on the purchase test (usually the test). DTX/DSX can easily detect the quality of cables, jumpers, connection modules, etc. The general test time can be completed within 15 seconds.
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