Common wiring system faults and troubleshooting Technology

In the acceptance process of the Integrated Wiring project, the acceptance test of the wiring system performance is very important. Such a test is usually called the authentication test, that is, the physical and Electrical Properties of The Link under test are checked according to the corresponding standards. Through the test, we can find various faults in the link, including wiring Map errors, cable Length problems, excessive Attenuation, and near-end crosstalk (NEXT) too high, Return Loss) too high. In order to ensure that the project is qualified, faults need to be solved in a timely manner, which puts forward high requirements on fault locating technology and positioning accuracy. Next we will give a brief introduction to the common faults and the two advanced fault locating technologies of the DSP4000 series cable Tester of FLUKE.
L HDTDR? (High Definition Time Domain Reflectometry)
High-precision time-domain reflection technology is mainly used to precisely locate faults with impedance changes. This technique sends a test signal in the tested linewise pair, and also monitors the signal reflection phase and intensity in the linewise pair to determine the fault type, the time when the signal is reflected and the speed at which the signal is transmitted in the cable can accurately report the specific location of the fault.
L HDTDX? (High Definition Domain Crosstalk)
High-precision Time-Domain Crosstalk Analysis technology is mainly used to precisely locate various faults that cause crosstalk. In the past, tests on near-end crosstalk could only provide results in the frequency domain of crosstalk, that is, they could only know the frequency MHZ at which the crosstalk occurred. They could not report the physical location of the crosstalk, such results far fall short of the need to solve crosstalk faults on the site. And HDTDX? The technique is to send test signals on a line pair and test crosstalk signals on adjacent lines in the time domain. Because the test is performed in the time domain, you can precisely locate the physical location of the crosstalk based on the time when the crosstalk occurs and the signal transmission speed. This is the only technology that can precisely locate near-end crosstalk and does not have a dead zone.
We will provide a detailed description of Common Faults in field testing combined with the above Testing Technology:
1. line chart (Wire Map) Error
-- It mainly includes the following error types: reverse join, error pair, and string bypass. For the first two kinds of errors, the general test equipment can be easily found, the test technology is also very simple, but it is difficult to find the string around. The error occurs because we did not follow the T568A or T568B rules when connecting the module or connector, as a result, although the two ends of the link physically implement 1 <-> 1, 2 <-> 2 ,...... 8 <-> 8 connections, but there is no guarantee that the pairs of 12, 36, 45, and 78 lines are twisted. This is a very common error ). As the twisted pair of the wire pair is damaged by the string winding, the crosstalk between the wire pairs is too large. This error may cause a decline in network performance or a deadlock on the device. However, the cable verification and testing equipment cannot find the winding position. Use the HDTDX of FLUKE DSP4000? We can easily find such errors, which can accurately report the start and end points of the cable, even if it exists in a part of the link ).
Legend 1: String Bypass
　
Non-standard wiring causes the twisted pair to be damaged. Such cables are in the bandwidth MHZ), such as 10BASE-T in a low-bandwidth network, and the network performance is not significantly affected. However, for networks with high bandwidth (MHZ), such as 100BASE-Tx, can significantly reduce network performance and cause device deadlocks.
2. Cable Wiring Diagram and Length issues-mainly including the following types of errors: open circuit, short circuit, and ultra-long. Open Circuit and short circuit have great impedance changes at fault points. For such faults, we can use the HDTDR of FLUKE DSP4000? Technology. The fault point causes different degrees of reflection on the test signal, and the impedance changes of different fault types are different, therefore, the test device can determine the fault type and distance by testing the signal phase change and the corresponding reflection delay. Of course, the accuracy of positioning is also determined by the value of the rated transmission rate NVP of the signal set by the device in this link. The principle of ultra-long link discovery is the same.
　　
36 pairs of tested cables are short-circuited at 1.0 meters. The right figure is HDTDR? Positioning analysis chart. The peak is down when a short circuit occurs, and the START edge is the fault start point. The positioning is very accurate.
　
Instance analysis:
In a design institute in Beijing, the access speed of a PC to other devices on the office network is very slow, while the access speed of other PCs on the same HUB is normal. The FLUKE DSP4000 cable tester was used to test and found that the link distance from the PC to the HUB was 361 feet m), and the attenuation failure was reported along with the long cable instrument. Cause analysis: the signal attenuation is too high due to the excessive cable length, which leads to the failure of the signal receiver to correctly identify the signal. The network error correction function requires the sender to resend the data, which leads to a reduction in network access performance.
The above are several representative physical faults. We can find that physical faults often lead to various electrical performance faults. Next we will continue to analyze several representative electrical performance faults.
1. attenuation)-Attenuation refers to the weakening of signal transmission along the link, which is caused by the electrical energy loss caused by the resistance of the cable and the electric energy leakage caused by the cable insulation material, signal attenuation is related to many factors, such as field temperature, humidity, frequency, and cable length. In the field test project, when the cable material is qualified, the attenuation is mostly related to the excessive length of the cable. We can easily know from the previous introduction that the link can be too long through HDTDR? For precise positioning.
The instance with a long link above has fully demonstrated the hdtdr of the DSP4000 cable tester? Powerful functions for attenuation positioning.
2. Nearby string winding NEXT) -- crosstalk is also called crosstalk in the communication field. It is similar to noise and is an unexpected signal transmitted from adjacent lines. The near-end Crosstalk Fault is common in the connection plug-in part of the link. Due to the nonstandard process during the end connection, for example, the untwisted part of the Joint Part exceeds the recommended 13mm, resulting in the cable twisting distance being damaged, this leads to high crosstalk at these locations. Of course, crosstalk occurs not only in the plug-in part, but also in the case of a piece of unqualified cable. For such faults, we can use the HDTDX of FLUKE DSP4000? It is easy to find their locations, whether it occurs in a plug-in or a link.
Instance analysis:
1. During the acceptance test of a project, we found that NEXT was unqualified. We passed the HDTDX test instrument? The fault is located. Results In the five categories of links under test, there was an excessively high NEXT section from 2.0 m to 7.8 m. After field inspection, it was found that a section of three categories of twisted pair wires were mixed in the link.
　 　
2. In the same project, it is found that two points in the link fail to pass NEXT. Also use HDTDX? We found that these two points are 2.0 and 7.5 in the Link, respectively. After inspection, we found that these two points were caused by too many wires opened when the modules were installed.
　
3. return loss (return loss) -- return loss is a signal reflection caused by unmatched link impedance. The mismatch mainly occurs in the connector, but may also occur in the place where the special impedance of the cable changes. Because four pairs of wires in a twisted pair are used in Gigabit Ethernet for two-way transmission of full duplex at the same time), the reflected signal may be mistaken for the received signal and cause confusion. Knowing the cause of the ripple loss is the signal reflection caused by impedance changes, we can use HDTDR for such faults? Technology is precisely positioned.
Example: locate a link with an unqualified return loss, HDTDR? The fault point is accurately reported at the 1.8 m module of the link.

How come with HDTDR ?, HDTDX? With this positioning technology, we can efficiently and accurately solve various cable faults. Note: The above two technologies are patent fault locating technologies registered by FLUKE .)