1.5 CABLE FOR RS232, RS422, RS485 SERIAL DATA LINKS

Where cables are listed as being for RS422 or RS485 serial data links, cable classed as "Low

Capacitance Data Cable for RS422/RS485 Serial Links" is required, in accordance with the

following requirements:

Where cables are listed as being for RS232, cable meeting the requirements for RS422 and RS485

will be more than adequate. Since RS232 is generally unsuitable for other than short local links, it

is unlikely that special purchase of cable meeting only the requirements of RS232 data links would

be worthwhile.

Low capacitance Data Cable suitable for RS422/RS485 Serial Links- Cable Specification:

Construction : Conductors formed into twisted pairs, with single overall foil

screen and overall tinned copper braid screen, with overall

insulating sheath.

Conductors: Tinned Copper, stranded. For mechanical reliability,

22AWG/0.34mm2 is the recommended minimum conductor

size.

Number of twisted pairs required: As shown on Converteam interconnection diagrams.

(3 pairs normally required. 2 pairs for 2-wire RS 485, or

where data flow is in one direction only. One of these pairs

is required for the 0V connection.)

Circuit voltage: 24V

Characteristic Impedance: 100 W to 120 W.

Capacitance (maximum): 45pF/m between conductors of one pair.

75pF/m between one conductor and all others and screen

connected together.

Resistance (maximum) 80 W/km

Velocity of Propagation (minimum) 70%

Notes:

1) If any cable run will exceed 200m, contact Converteam - cable of lower capacitance may

be necessary.

2) Each cable should only carry one Serial Data Link.

3) When data flow is known to be in one direction only, requiring only one pair for data (e.g.

as in the case of printer connections), a 2-pair cable may be used, with the second pair used

as the 0V connection.

4) The number of pairs required will be indicated on Converteam Schedules/Interconnection

Diagrams.

The following cable types are known to have suitable electrical properties, but the Cable Contractor

must check that the cable construction and materials are acceptable for the application:

a) For four-wire links, using the third twisted pair as the ground connection between serial

ports: Belden type 3108A, (22 AWG).

Belden type 8103 (24 AWG),has suitable electrical properties but the conductor size is

smaller than recommended by Converteam, and may not be accepted by the Classification

Society.

b) For two-wire links, using the second twisted pair as the ground connection between serial

ports: Belden type 3107A, (22 AWG). Belden type 8102 (24 AWG) has suitable electrical

properties but the conductor size is smaller than recommended by Converteam, and may not

be accepted by the Classification Society.

求助大家帮忙选一下,有没有这方面的资料!

我们是国内最早生产RS485电缆的厂家之一。

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通用型现场总线系列电缆

      特性阻抗为120Ω的双绞屏蔽电缆广泛用于RS485/422、CANBUS等总线，该系列电缆规格很多，请提供电缆的敷设环境、通信速率、最大无中继传输距离等参数，我们将依照具体情况推荐最适当的产品。一般推荐如下：

     普通双绞屏蔽型电缆 STP-120Ω（for RS485 & CAN） one pair 20 AWG ，电缆外径7.7mm左右，蓝色护套。适用于室内、管道及一般工业环境。使用时，屏蔽层一端接地！

      普通双绞屏蔽型电缆 STP-120Ω（for RS485 & CAN） one pair 18 AWG ，电缆外径8.2mm左右，灰色护套。适用于室内、管道及一般工业环境。使用时，屏蔽层一端接地！

铠装双绞屏蔽型电缆 ASTP-120Ω（for RS485 & CAN） one pair 18 AWG ，电缆外径12.3mm左右，黑色护套。可用于干扰严重、鼠害频繁以及有防雷、防爆要求的场所。使用时，建议铠装层两端接地，最内层屏蔽一端接地！

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