1, the classification of network cable
The standard of the three types of cable is “CAT3â€, with a bandwidth of 10M. It is suitable for 10M network and has basically been eliminated. The standard of Category 5 cable is “CAT5â€, and the bandwidth is 100M. It is suitable for networks below 100M; Super Category 5 cable. The standard is "CAT5E" with a bandwidth of 155M, which is currently the mainstream product; the standard for Category 6 cable is "CAT6", and the bandwidth is 250M. It is used to set up Gigabit network and is the trend of future development.
2, the determination method
Twisted pair test in a high temperature environment, look at 35 degrees Celsius to 40 degrees Celsius, the rubber outside the cable will not become soft, really the cable will not be soft, false is not necessarily; Copper wires are generally used in twisted-pair cables as cores, which are relatively soft, and some unscrupulous manufacturers add other metal elements to the copper in order to reduce costs during production. The wires are hard and difficult to bend. Easy to break; also, really outside the network cable is also flame-retardant, and some of the fake is not flame retardant, does not meet the safety standards, try to buy.
These tricks alone are still far from being able to deal with all counterfeit network cables. Some counterfeiters use the cores of the three types of cables to put on the outer skin of the five types of lines. This method of counterfeiting is very subtle and difficult to distinguish with the naked eye. This type of false network cable can also reach the transmission speed of the Category 5 cable within a short distance. However, when the distance is long, there will be problems such as slow transmission speed, loss of transmitted data packets, or simply no signal detection.
For this feature, you can take a piece of network cable to test: Take a hundred meters of network cable to connect the computer network, use the "System Monitor" in Windows 98 or "Network Monitor" in Windows 2000 to test it yourself, if the test speed reaches 100Mbps, This indicates that it is a Category 5 twisted pair. If it is only 10 Mbps, it means that the cable used is a Category 3 conductor.
This method can not only correctly distinguish between Category 3 and Category 5 cables, but also can be used to test whether the twisting degree of each pair of conductors in a twisted pair cable is in line with the standard. At the same time, it can also measure whether the metal media in the conductor is qualified. It should be noted that the length of the twisted pair should be a standard length of 100 meters when the network speed test is performed, otherwise the measured data has no practical significance.
Sintered NdFeB magnets are prepared by the raw materials being melted in a furnace, cast into a mold and cooled to form ingots. The ingots are pulverized and milled; the powder is then sintered into dense blocks. The blocks are then heat-treated, cut to shape, surface treated and magnetized.
As of 2012, 50,000 tons of neodymium magnets are produced officially each year in China, and 80,000 tons in a "company-by-company" build-up done in 2013. China produces more than 95% of rare earth elements, and produces about 76% of the world's total rare-earth magnets.
Neodymium magnets are graded according to their maximum energy product, which relates to the magnetic flux output per unit volume. Higher values indicate stronger magnets and range from N35 up to N52. Letters following the grade indicate maximum operating temperatures (often the Curie temperature), which range from M (up to 100 °C) to EH (200 °C).
Sintered Nd2Fe14B tends to be vulnerable to corrosion, especially along grain boundaries of a sintered magnet. This type of corrosion can cause serious deterioration, including crumbling of a magnet into a powder of small magnetic particles, or spallingof a surface layer.
This vulnerability is addressed in many commercial products by adding a protective coating to prevent exposure to the atmosphere. Nickel plating or two-layered copper-nickel plating are the standard methods, although plating with other metals, or polymer and lacquer protective coatings are also in use.
Neodymium magnets have replaced alnico and ferrite magnets in many of the myriad applications in modern technology where strong permanent magnets are required, because their greater strength allows the use of smaller, lighter magnets for a given application. Some examples are:
ï‚·Head actuators for computer hard disks
ï‚·Magnetic resonance imaging (MRI)
ï‚·Mechanical e-cigarette firing switches
ï‚·Locks for doors
ï‚·Loudspeakers and headphones
ï‚·Magnetic bearings and couplings
ï‚·Electric motors:
ï‚·Cordless tools
ï‚·Servomotors
ï‚·Lifting and compressor motors
ï‚·Synchronous motors
ï‚·Spindle and stepper motors
ï‚·Electrical power steering
ï‚·Drive motors for hybrid and electric vehicles. The electric motors of each Toyota Prius require 1 kilogram (2.2 pounds) of neodymium.
ï‚·Actuators
ï‚·Electric generators for wind turbines (only those with permanent magnet excitation)
ï‚·Direct-drive wind turbines require c. 600 kg of PM material per megawatt
ï‚·Turbines using gears require less PM material per megawatt
ï‚·Toys
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Jinyu Magnet (Ningbo) Co., Ltd. , https://www.magnetbonwin.com