Shielded cable is a transmission line that uses a metal mesh braided layer to wrap the signal line. The braiding layer is usually red copper or tinned copper. Wire and cable industry is China's second largest industry after the automobile industry, product variety satisfaction rate and domestic market share are more than 90%. This article talks with you about the difference between shielded and unshielded cables.



A shielded cable connected to the specification, as well as a number of connectors between the two devices, transmits information between them, in which case, the high-frequency interference between the transmission frequency of 1MHZ - 300MHZ can be reduced by 100 times, while the symmetrical pair cable still cannot reduce the non-surge interference by 30 times. In this case, common-mode transmission cannot be changed to differential mode transmission.

Surge interference is mainly caused by lightning electromagnetic field, electrostatic discharge, etc. According to Lenz's law, the same data cable shielding has attenuation function on the low-frequency part of the surge interference. In fact, the surge current flowing through a loop made of "green and yellow" wires and shielding of the data cable creates an electromagnetic field in the opposite direction to a lightning or electrostatic field. Therefore, the shielding layer of the data cable provides the same reduction effect on the low-frequency portion of the surge interference.

There are several reasons to use the shielding layer of data cables:

1. Electromagnetic field

All fluctuations in the current flowing through a wire produce an electromagnetic field, in which if there is any loop area, an induced current will be generated in the loop line, and a voltage will be generated at the terminal at the break point of the line, that is, if the two ends of the cable's shield are not connected to the device housing. An induced voltage is generated at the input end. Because, in the case of lightning and electrostatic discharge, the electromagnetic field has electrical energy, it is necessary to use a shielding layer to shield the electromagnetic field.

2. Circular line of shell ground wire

The circular circuit of the shell ground wire can sense and receive electromagnetic fields. The enclosure ground line is the area of the loop between the cable and the adjacent enclosure ground line of the device. It is common for data cables powered by information networks to be laid far away, and this cable is easy to establish a circular line of a shell ground wire, which is more easily suitable for entering the electromagnetic field of lightning and electrostatic discharge.

3. The energy phenomenon of power surge

The energy of a lightning surge can be regarded as a high-power generator of an electromagnetic field that induces electrical energy or voltage in a vertical loop area. The overvoltage intrusion on the incoming line of the building is the main reason for the damage of the local area network. Electrostatic discharge is generated frequently, the discharge energy does not increase, it is similar to lightning discharge, it may damage the communication card.

4, common mode resistance

The common-mode impedance on the grid is equivalent to the damage factor of the communication card. When the data cable of the LAN is connected to the terminal of the power supply line of the electrical machine, there is a common mode impedance. Due to the voltage transition process generated by the electrical machine, the terminal is subjected to severe dV/dt changes, and because the data cable is not a shielded cable, the communication card stops working due to information interruption. Every quarter to replace the communication card, the number of use is large.

Qingdao Tianxing Cable Co., Ltd. focuses on the production of customized wire and cable manufacturers, main: fire wire and cable, power cable, control cable and other products, exported to more than 40 countries and regions around the world, the annual production capacity of 1 billion yuan. 6000 square meters of storage, standing hundreds of millions of inventory, order demand for rapid distribution and delivery, large prices more favorable. Hotline: 16678668098