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Q How to quickly estimate the ampacity of small cross-section (≤1mm^2) wires in cable assemblies?
A There are many factors involved in the current carrying capacity of wires in cable assemblies, such as conductor material, insulation thermal resistance, laying conditions, ambient temperature, operating temperature, system voltage drop requirements, and rated current of connectors. We can use 10 times the cross-sectional area method to roughly estimate its current carrying capacity. For example, 28AWG wire has a cross-sectional area of 0.08mm^2, and its current carrying capacity is about 1A.
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Q What are the shielding methods of connectors in cable assemblies?
A Some connectors have metal shielding shells, such as USB, D_Sub etc., and some connectors do not have a shielding structure, but add a copper foil or aluminum foil shielding layer during the component manufacturing process, such as common injection-molded plug connectors, The copper foil or aluminum foil is perfectly overlapped with the connector and cable braid by 360° girth welding, which has very good shielding performance.
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Q Why can the CAT5e cable and the 250M CAT6 cable be applied to Gigabit Ethernet?
A First of all，Mbps is the data rate, which describes the throughput of the system and belongs to the data link layer.Then MHz is the unit of frequency, the description of electrical signals, belongs to the physical medium layer. Gigabit Ethernet refers to data rate, while 250 megabits refers to bandwidth.
The theoretical value formula is obtained from Shannon's theorem: bandwidth = bandwidth factor x rate, for example: the bandwidth is 20GHz, if the pulse amplitude modulation (0.375) of PAM4 is used, the theoretical rate of 56GHbps can be achieved.
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Q What is EtherCAT?
A EtherCAT is a field bus protocol for automation introduced by Beckhoff, and it is one of the most widely used protocols on the market. Its essence is also based on the IEEE Ethernet protocol, and supports almost all topology types, such as line, tree, and star topology. It has the characteristics of good real-time performance, high security and reliability, high compatibility and low implementation cost.
EtherCAT cable is an Ethernet cable developed according to the EtherCAT protocol. It can adopt star-pair and twisted-pair structures. The cable specification can be 20AWG~26AWG. Choose the most suitable structure and specification according to the specific use environment. At the same time, the PROFINET cable also supports the EtherCAT protocol.
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Q Some common misunderstandings of IP protection level
A In industrial production, we often come into contact with IP protection level. According to the national standard GB 4208-2008 (same as IEC 60529:2001), the definition of protection level is as follows. The degree of protection provided by the entry of foreign objects or water is simply understood to be waterproof and dustproof. The enclosure refers to the part of the device that protects the device from certain external influences and prevents direct contact in all directions. For example some connectors, sensors, cable glands, etc. Dangerous parts refer to moving parts that are dangerous when approached and live parts that are subject to certain external influences that can cause electric shock. Therefore, to a certain extent, the cables used in certain occasions are dangerous parts, and the IP protection level is a requirement for the outer casing. Therefore, it is incorrect to propose an IP protection level for cables. Of course, some enclosures are connected to cables, and cables are also considered in IP protection class experiments.
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Q What is Delay Skew?
A Delay Skew refers to the time difference between the signals arriving at the receiving end on different signal lines. Because each line pair has a different length, the delay is also different, resulting in the difference between the four pairs of lines. So, why design with different twist pitches? Mainly because different twisted pair pitches can improve crosstalk between pairs (NEXT, FEXT). Theoretically, the more the twist pitch is staggered, the more obvious the improvement will be. However, the pitch of the twisted pair cannot be staggered endlessly, otherwise the signals on the four pairs of wires will enter the same and go differently, and the delay difference will be too large. After the receiving port receives the signal, there will be an error in the time alignment processing of the square wave of the signal, and the frame restoration will be wrong, causing the signal transmission to be unstable or fail.
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Q Why should the insulation of 10 Gigabit Ethernet cable be foamed? Process explanation of physical foaming? What are the advantages of physical foaming?
A Physical foaming is to inject gas directly into the insulation extrusion process to realize foaming. Physical foaming uses gas as foaming agent, so it eliminates the disadvantages of chemical foaming, that is, there is no residue or water produced by chemical foaming method in the insulation, which greatly reduces the dielectric loss of insulation. Physical foaming can eliminate many process limitations of chemical foaming, It is easy to make small cell, uniform foaming and high-quality insulation.
10 Gigabit Ethernet cable insulation foam has the following advantages:
1. Reduce the dielectric constant of the insulating layer and effectively reduce the diameter of the insulated wire
2. Reduce the outer diameter of the finished product, and the bending radius of the cable is smaller, which is more conducive to installation and laying
Reducing the insulated wire diameter can better adapt to the connector
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Q What is star-twist, and what are the advantages of star-twist compared with pair-twist ?
A Star-twist means that every four insulated core wires form a 4-core insulation group according to a certain pitch and stranding direction, and the two insulated core wires at the diagonal position in the 4-core insulation group form a communication loop.
Compared with twisted pair cables, star twisted cables have the following advantages:
1) Stable electrical performance
2) Smaller cable outside diameter
3) Lighter weight
4) Smaller bending radius
6) Reduce wiring space and material cost
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Q What is Coaxial Cable?
A Coaxial Cable is a kind of wire and signal transmission line, which is generally composed of four parts: the innermost part is a copper conductor, the outside of the cable is covered with a layer of plastic insulator, and the outside of the insulator is covered by a layer of braided mesh, and the outside of the braided mesh Then wrap a layer of plastic as a protective sheath.
Coaxial cable can be used for the transmission of analog signals and digital signals, and is suitable for a variety of applications, the most important of which are video transmission, laser cutting system signal transmission, machine vision transmission system applications, medical system applications, etc.
1) Stable and reliable data transmission;
2) Good shielding effect ensures excellent anti electromagnetic interference performance;
3) Fast transmission speed and long transmission distance;
4) Special product design can meet dynamic application requirements;
5) Wide range of applications and high cost performance
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Q PROPAGATION DELAY
A Propagation Delay refers to the time required for a signal to be transmitted from the source to the destination in a communication system.
The main factors affecting cable propagation delay:
1. The dielectric constant of the insulating medium and its dielectric constant, the dielectric constant of the insulation of different materials is quite different, the vacuum is the best medium, the signal propagation speed in it is the fastest, so high-performance data cables often use foaming technology to Reduce the dielectric constant of the insulation to achieve better transmission.
The twisted length includes pair-twist pitch and cable pitch. Different twisted length make the signal propagation distance different. The smaller the twisted length, the longer the distance, and the greater the delay.
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