What kind of wire and cable knowledge do you need to master in weak electrical security?

There are many types of weak electric cables. The cable types used in each system are different and their functions are different. It is necessary for friends who are weak in electricity to understand the commonly used weak electric cables.
First, the definition of wire and cable
Wire and cable refers to materials used in power, communications, and related transmission applications. There are no strict boundaries between "wires" and "cables." A product having a small number of cores, a small product diameter, and a simple structure is generally referred to as a wire, and a non-insulated product is called a bare wire, and the other is called a cable.
Second, weak electric cable naming principle
1. Content included in the product name:
(1) Product application or size class name
(2) product structure materials or types;
(3) Important or additional features of the product
Basically named in the above order, sometimes in order to emphasize important or additional features, the features are written before or before the corresponding structure description.
2, the order of structure description
The product structure is described from the inside to the outside: conductor -> insulation -> inner sheath -> outer sheath.
3, simplified
Some structural descriptions are either written or abbreviated without causing confusion. E.g:
SYV 75-5-1 (A, B, C) S: RF Y: Polyethylene insulation V: PVC sheath A: 64 series B: 96 series C: 128 series 75: 75 ohms 5: wire diameter 5MM 1: represents a single core
SYWV 75-5-1 S: ​​RF Y: Polyethylene insulation W: Physical foaming V: PVC sheath 75:75 ohms 5: Cable outer diameter is 5mm 1: Represents single core


RVVP2*32/0.2 R: Cord VV: Double sheathed wire P shield 2: 2 core multi-strand wire 32: 32 copper wires per core 0.2: Each copper wire has a diameter of 0.2 mm
ZR-RVS2*24/0.12 ZR: Flame Retardant R: Cord S: Twisted Pair 2: 2 core multi-strand wire 24: 24 copper wires per core 0.12: Each copper wire has a diameter of 0.12mm
Third, the composition of weak electric cable
It consists of an inner conductor, an insulation, an outer conductor and a sheath from the inside out;
Inner conductor: Since the attenuation is mainly caused by the resistance of the inner conductor, the inner conductor has a great influence on the signal transmission.
Insulation: affects attenuation, resistance, return loss and other properties
Outer conductor: return conductor, shielding
Fourth, the common cable code meaning
RVVP : copper core PVC insulated and sheathed PVC sheathed flexible cable voltage 300V/300V 2-24 core use: instrument, instrument, intercom, monitoring, control installation
KVVP: PVC sheathed braided shielded cable Uses: Signal transmission, control, measurement of electrical, instrumentation, and distribution equipment
SYWV ( Y ), SYKV cable TV, broadband network dedicated cable structure: (coaxial cable) single oxygen-free round copper wire + physical foamed polyethylene (insulation) + (tin wire + aluminum) + polyvinyl chloride (polyethylene) )
RVV PVC insulated flexible cable Uses: household appliances, small power tools, instruments and power lighting
AVVR PVC sheathed flexible cable
RV, RVP PVC insulated cable
RVS and RVB are suitable for household appliances, small power tools, instruments, meters and power lighting connection cables.
BV, BVR PVC insulated cable Uses: Suitable for electrical instrumentation equipment and power lighting fixed wiring
V. Examples of selection of common weak current cables
The distance between the video line camera and the monitoring host is ≤200 meters, and the SYV75-3 video cable is used. The distance from the camera to the monitoring host is >200 meters, using the SYV75-5 video cable. Network digital video surveillance, camera transmission using twisted pair transmission, such as cat5e, cat6 and so on.
The distance between the pan/tilt control line and the controller is ≤ 100 m, and the RVV 6×0.5 sheathed wire is used. The distance between the pan/tilt and the controller is > 100 m, and the RVV6×0.75 sheathed wire is used. In practice, RVVP2*075 is generally used.
Cables used in building intercom systems are mostly RVV, RVVP, SYV and other cables.
Six, the difference between common weak electric cables
The difference between SYV and SYWV: SYV is a video transmission line, insulated with polyethylene. SYWV is an RF transmission line with physical foam insulation. For cable TV.
RVS differs from RVV 2 core: RVS is a twisted pair of two-core RV wires with no outer jacket for broadcast connections. The RVV 2-core cable is directly cabled and has an outer jacket for power supply and control signals.
RVV and KVV RVVP and KVVP difference: The line used in RVV and RVVP is composed of a flexible wire composed of multiple thin copper wires, that is, RV lines. The wire used in KVV and KVVP is a hard wire consisting of a single thick copper wire, that is, a BV wire.
The difference between AVVR and RVVP: AVVR refers to unshielded cable with wire diameter less than 0.5MM, and RVVP refers to shielded cable with wire diameter greater than or equal to 0.5MM.
RVS differs from RVV 2 core: RVS is a twisted pair of two-core RV wires with no outer jacket for broadcast connections. The RVV 2-core cable is directly cabled and has an outer jacket for power supply and control signals.

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What disease can dry air cause

It will not lead to specific diseases, but only some hazards.

1. It is easy to cause excessive loss of body water, infect diseases and accelerate aging. In a dry environment, when we get up every morning, we will feel dry mouth, tight muscles and low mood. Especially for women, the skin's muscle fibers are composed of a large amount of water-soluble collagen. Drying makes the muscle fibers shrink due to rapid water loss. Over time, the muscle fibers may break, and the skin will have unrecoverable wrinkles and aging.

2. Easy to cause the spread of bacteria. Dry air is the main reason for the increase of dust and suspended particles, while bacteria can not exist alone and often adhere to dust. The elderly and young children have weak physical resistance and are vulnerable to bacteria and viruses. Warm and dry is the best environment for the breeding and transmission of many viruses and bacteria.



Tips for reducing air drying:

1. Put the peel on the heater

Usually after eating oranges and grapefruits, don't throw away the peel. The moisture content of these peels is large. If the car information is placed on the heating, it can also play a certain humidification effect. In addition, it can also emit a fragrant fruit fragrance and purify the air.

2. A basin of water with a wet towel

Still put a basin of water, but put a wet towel on the basin. Half of the towel is immersed in the water and half is out of the water. The contact surface between water and air in the washbasin is small, so it volatilizes slowly. After building a wet towel, the contact surface becomes larger, and the humidification effect is naturally much better. Moreover, the towel can continuously absorb water from the basin and is not easy to dry.

Reference: people.com - 9 Tips to teach you to fight against dry winter. Science has proved that the harm of dry air to human body is very serious. Medical experts point out that under normal circumstances, the appropriate health humidity of the human body is between 45% RH and 65% RH, while in autumn and winter, the air humidity in northern China is generally below 30% RH, which can not meet the health requirements of the human body.

Another simple and effective way is to put an Aroma Diffuser in the room. It can take effect effectively and immediately, humidify the air and solve the problem of air drying. The ultrasonic aroma diffuser is required, and the fog is sprayed out through vibration


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