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Home > Industry Information > The defonition of weak current cable and examples of its selection
Industry Information

The defonition of weak current cable and examples of its selection

2018-11-16


Definition of weak current cable

Wire and cable refers to materials used in power, communications, and related transmission applications. There are no strict boundaries between "wires" and "cables." Generally, a product with a small number of cores, a small product diameter, and a simple structure is called a wire, a non-insulated wire is called a bare wire, and the other is called a cable; a conductor having a large cross-sectional area (greater than 6 square millimeters) is called a large wire. Small (less than or equal to 6 square millimeters) is called a small wire, and insulated wire is also called a wire. Wire and cable mainly includes bare wires, electromagnetic wires and insulated wires for electrical appliances, power cables, communication cables and optical cables.

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

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

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

Weak cable selection example

1. 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.

2, PTZ control line PTZ and controller distance ≤ 100 meters, with RVV6 × 0.5 sheathed wire. The distance between the pan/tilt and the controller is > 100 m, and the RVV6×0.75 sheathed wire is used.

3, the lens control line uses RVV4 × 0.5 sheathed wire.

4, decoder communication line should use RVV2 × 1 shielded twisted pair

Selection of weak current cable

Video signal transmission generally adopts direct modulation technology in the form of baseband frequency (about 8MHz bandwidth). The most commonly used transmission medium is coaxial cable; coaxial cable is specially designed to transmit video signals, its frequency loss, image distortion, The amplitude of the image attenuation is relatively small, and the task of transmitting the video signal can be well accomplished.

The special SYV75 ohm series coaxial cable is generally used; the common model is SYV75-5 (it has a non-relay transmission distance of 300-500m for video signals); when the distance is long, SYV75-7 and SYV75-9 are required. Shaft cable (in actual engineering, the non-relay transmission distance of the thick cable can reach more than 1km)

The communication cable is generally used in an image pickup device equipped with an electric pan/tilt head and a motorized lens. The remote control decoder is required to be installed in the field; the communication transmission cable between the field decoder and the video matrix switching host of the control center is generally adopted. 2-core shielded communication cable (RVVP) or Category 3 twisted pair UTP, the cross-sectional area of each core is 0.3mm2 ~ 0.5mm2; the basic principle of selecting communication cable is that the longer the distance, the larger the wire diameter; the basic requirements of RS-485 communication The communication distance is 1200m, but in the actual engineering, the RVV2-1.5 sheathed cable can be used to extend the communication length to more than 2000m.

The control cable usually refers to a multi-core cable used to control the pan/tilt and the electric variable lens; one end of the control cable is connected to the pan/tilt of the controller or decoder, the motorized lens control terminal, and the other end is directly connected to the pan/tilt, On the corresponding terminals of the motorized lens; the control cable provides DC or AC voltage, and the general distance is very short (sometimes less than 1m), basically there is no interference problem, so no shielded wire is needed.

Most commonly used control cables use 6-core or 10-core cables, such as RVV6-0.2 and RVV10-0.12; 6-core cables are connected to the top, bottom, left, right, automatic, and common 6 terminals of the pan/tilt, 10 cores. In addition to the six terminals of the head, the cable also includes zooming, focusing, aperture, and common four terminals of the motorized lens. In the monitoring system, the control cable from the decoder to the pan/tilt and the lens is short. Generally, no special requirements are required; however, the distance from the controller of the central control room to the pan/tilt and the electric lens is as small as several tens of meters, and several hundred meters, and the control cable needs to have certain requirements, that is, the wire diameter is thick, such as selection. RVV10-0.5, RVV10-0.75

The sound Monitoring cable is generally a 4-core shielded communication cable (RVVP) or a Category 3 twisted pair UTP with a cross-sectional area of 0.5 mm2 per core.

The audio signal of the monitor head in the monitoring system is transmitted to the central control room using the point-to-point wiring method, which is transmitted with high voltage and small current. Therefore, an unshielded 2-core cable can be used, such as RVV2-0.5.

RVV2*0.3 (signal line) and RVV4*0.3 (2-core signal + 2-core power supply) cable are generally used between the front-end detector and the alarm controller; the two cores are generally used between the alarm controller and the terminal security center. Signal line

The shielded wire or twisted wire of the signal wire or the ordinary sheathed wire needs to be determined according to the requirements of various brand products; the coarse rule of the signal wire diameter is determined according to the distance and quality of the alarm controller and the center; alarm control The power supply of the device is generally powered by local power instead of centralized power supply in the control room. The line is short, generally adopts RVV 2×0.5” or above; the power supply of perimeter alarm and other public area alarm devices generally adopts centralized power supply mode, and the line is longer. Generally adopt RVV2*1.0" or above specifications

Cables used in building intercom systems are mostly RVV, RVVP, SYV and other cables.

It has the functions of transmitting voice, data and video images, and the cable requirements are also reflected in the quality of voice transmission, the rate of data transmission, the quality and speed of video image transmission.

The cable for transmitting voice signals and alarm signals is mainly RVV4-8*1.0

Video transmission is based on SYV75-5 cable

Some systems must use RVVP cable in the system for fear of external interference or grounding.

Direct button type building video intercom system line standard:

The video terminals, two-way sound and remote unlocking of each indoor unit are connected to the door machine by bus, but each call line is directly connected to the door machine.

--Video coaxial cable SYV75-5, SYV75-3

-- A 4-core unshielded or shielded sheathed cable (AVVR4, RVV4 or RVVP4, etc.) for the microphone/speaker/lock line

--The power cord uses a 2-core sheathed cable (AVVR2, RVV2, etc.)

-- 2-wire shielded wire for call line (RVVP2)

Digital coded button video intercom system:

--The main line includes video coaxial cable (SYV75-5, SYV75-3, etc.)

--Power cord (AVVR2, RVV2, etc.)

--Audio/data control line (RVVP4, etc.)

-- Household signal line (RVVP6, etc.)

The difference between 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 the unshielded cable with a wire diameter less than 0.5MM, and RVVP refers to the shielded cable with a 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. RVV 2-core cable is placed directly into the cable, with outer sheath for power supply, control signals, etc.

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