RS‑485 cable
RS-485 is strictly a serial communications standard (officially called TIA/EIA-485), and not a specific designation of a cable type.
This standard defines how equipment transmits data via a differential signal. The RS-485 cable on the market actually means a twisted shielded cable specially designed for RS-485 bus links. It is commonly used in industrial and automation environments requiring long distance communications, strong immunity to interference, and support for multipoint communications.
Features
Although RS-485 is an electrical standard, in practice, Communication cables specifically designed for RS-485 are generally used.. These cables generally have the following characteristics :
- Twisted pair structure : differential signal uses twisted pair to reduce electromagnetic interference (EMI).
- Shielding : to enhance protection against interference, they are often equipped with braided or foil shielding.
- Impedance matching : the characteristic impedance is generally around 120 Oh, compliant with RS-485 bus requirements.
- Multi-conductor structure : some models have multiple twisted pairs, allowing the transmission of several signals or the integration of a power supply.
ZMS CABLE offers RS-485 communication cables specifically designed to meet industrial requirements.
We manufacture one or two shielded twisted pair cables. And we can also customize them according to your requirements. These cables provide excellent immunity to electromagnetic interference and stable performance. They strictly comply with RS-485 standards in terms of structure and impedance, and are highly appreciated in the field of industrial communications.
Construction
- Drivers : Multi-stranded copper wires forming one or more twisted pairs for differential signal transmission.
- Isolation : Each conductor is individually insulated, usually made of polyethylene (PE) or vinyl polychloride (PVC), to guarantee good electrical insulation.
- Shielding (optional) : Aluminum foil and/or copper braid serving as a shield to reduce electromagnetic interference (EMI).
- Outer sheath : Protective coating against wear and external aggression, usually PVC or polyurethane (PUR) for good flexibility and resistance.
Settings
| Electrical properties to 20 °C | |
| Loop resistance | max. 175,2 Ω/km |
| Isolation resistance | min. 5 GΩ·km |
| Mutual capacity | max. 60 nF/km (has 800 Hz) |
| Characteristic impedance | 100 Ω to 120 Oh |
| Mitigation | 100 kHz : ≤ 0,9 dB/100 m 1 MHz : ≤ 2,5 dB/100 m 10 MHz : ≤ 7,9 dB/100 m |
| Diaphonie (Near-end) | 1 MHz : ≥ 50 dB 10 MHz : ≥ 40 dB |
| Speed of propagation | 0,66 c |
| Transfer impedance | 1 MHz : ≤ 50 mΩ/m 10 MHz : ≤ 100 mΩ/m |
| Tension de service max. | 250 V (excluding power applications) |
| Test voltage | soul/soul : 1500 V soul/screen : 1500 V |
RS-485 Cable Applications
- Industrial automation : fieldbus connection, programmable controllers (PLC), speed variators, sensors and actuators.
- Building Control Systems (BMS) : technical management of buildings, HVAC regulation, access control and centralized monitoring.
- Multipoint networks : communication between several devices on the same bus line up to 1200m.
- Infrastructure et transport : railway signaling, automation of production lines, communication in port or airport facilities.
- Home automation integration : lighting control, blinds, safety and energy consumption.
- Measurement and instrumentation systems : remote data collection, environmental monitoring and process control.
Technical data
Industrial applications and harsh environments
| Shielding | Pairs (PR) | AWG | Sheath | Homologation |
| SF/UTP | 1 | 18 AWG | PVC | CMG/ITC, PLTC/600V TC |
| SF/UTP | 1 | 22 AWG | PVC | CM/PLTC |
| SF/UTP | 1,5 | 22 AWG | PVC | CM/PLTC |
| SF/UTP | 2 | 22 AWG | PVC | CM/PLTC |
| SF/UTP | 3 | 22 AWG | PVC | CM/PLTC |
| SF/UTP | 4 | 22 AWG | PVC | CM/PLTC |
| SF/UTP | 1 | 22 AWG | CPE | CM/PLTC, UL, Direct burial |
| SF/UTP | 1,5 | 22 AWG | CPE | CM/PLTC, UL, Direct burial |
| SF/UTP | 2 | 22 AWG | CPE | CM/PLTC, UL, Direct burial |
| SF/UTP | 3 | 22 AWG | CPE | CM/PLTC, UL, Direct burial |
| SF/UTP | 4 | 22 AWG | CPE | CM/PLTC, UL, Direct burial |
| SF/UTP | 3 | 22 AWG | PVC | AIA, CM/PLTC |
| SF/UTP | 4 | 22 AWG | PVC | AIA, CM/PLTC |
| SF/UTP | 1 | 22 AWG | PVC | IS, CM/PLTC |
| SF/UTP | 2 | 22 AWG | PVC | IS, CM/PLTC |
| SF/UTP | 1 | 22 AWG | PVC | IS, CM/PLTC |
| SF/UTP | 2 | 24 AWG | PVC | IS, CM/PLTC |
| SF/UTP | 3 | 24 AWG | PVC | IS, CM/PLTC |
| SF/UTP | 4 | 24 AWG | PVC | IS, CM/PLTC |
Applications for maritime transport
| Shielding | Pairs (PR) | AWG | Sheath | Ranking |
| SF/UTP | 1 | 22 AWG | TP LSNH | CMC/PLTC |
| SF/UTP | 1,5 | 22 AWG | TP LSNH | CMC/PLTC |
| SF/UTP | 2 | 22 AWG | TP LSNH | CMC/PLTC |
| SF/UTP | 3 | 22 AWG | TP LSNH | CMC/PLTC |
| SF/UTP | 4 | 22 AWG | TP LSNH | CMC/PLTC |
Light industrial applications
| Shielding | Pairs (PR) | AWG | Sheath | Ranking |
| SF/UTP | 1 | 24 AWG | PVC | CMG |
| SF/UTP | 2 | 24 AWG | PVC | CMG |
| SF/UTP | 3 | 24 AWG | PVC | CMG |
| SF/UTP | 4 | 24 AWG | PVC | CMG |
| SF/UTP | 1 | 24 AWG | LSNH | CMG |
| SF/UTP | 2 | 24 AWG | LSNH | CMG |
| SF/UTP | 3 | 24 AWG | LSNH | CMG |
| SF/UTP | 4 | 24 AWG | LSNH | CMG |
| SF/UTP | 1 | 24 AWG | PVC | CMP |
| SF/UTP | 2 | 24 AWG | PVC | CMP |
| SF/UTP | 3 | 24 AWG | PVC | CMP |
| SF/UTP | 4 | 24 AWG | PVC | CMP |
| SF/UTP | 1 | 24 AWG | FEP | CMP |
| SF/UTP | 2 | 24 AWG | FEP | CMP |
Noticed :
SF/UTP：Pair shielded/without general shielding (global screen).
TP LSNH：Halogen -free thermoplastic (Low Smoke Zero Halogen)。
PVC：Vinyl polychloride.
FEP：Fluoropolymer (Teflon).
CMC / CMG / CMP / PLTC：Cable ratings according to UL/NEC (CMC : Communications, CMG : General Purpose, CMP : Plenum, PLTC : Power Limited Tray Cable).
RS-485 cable vs. other communication cables
| Features | RS-485 cable | RS-232 | RS-422 | Ethernet (Cat 6) | CAN Bus | Fiber optics |
| Related standard | EIA-485 (differential bus) | EIA-232 (point-to-point serial link) | EIA-422 (differential connection) | ISO/IEC 11801 | ISO 11898 (automotive/industry) | IT-T G.652 / G.657, ISO/IEC 11801 |
| Cable structure | Shielded twisted pairs | Single cable, often unshielded | Shielded twisted pairs | Twisted pairs (UTP/FTP/STP) | Shielded twisted pairs | Glass or plastic fibers |
| Transmission distance | Until 1200 m at low flow | < 15 m | environ 1200 m | 100 m (copper) / several km (fibre opt.) | environ 40 m to 1 Mb/s ; until 1 km at low flow | Until 100 km (depending on type and flow) |
| Transmission speed | Until 10 Mbit/s (depending on distance) | Max. 20 kbit/s | Until 10 Mbit/s | 1 has 10 Gbit/s | 1 Mbit/s (classic), until 5 Mbit/s | Of 100 Mbit/s to several Tbit/s |
| Multipoint connection | Oui, until 32 nodes per bus | Non | Limit (point-to-point or multi-drop) | Oui, via switches and routers | Oui, multi-node bus | Oui (via active equipment) |
| Interference immunity | High (thanks to shielding and differential signal) | Weak | Good | Good (according to shielding) | Good | Excellent |
| Typical applications | Automation, home automation, industrial control | Old serial connections (PC, modems) | Industry, point-to-point connections | Local networks, Internet | Automobile, robotics, automation | Telecoms, data centers, long distance connections |
| Cost | Low to medium | Very weak | Low to medium | AVERAGE | AVERAGE | Higher |
Conclusion
The RS-485 cable stands out for its excellent compromise between reliability, scope and cost. Unlike distance-limited RS-232 and more expensive Ethernet or fiber optic cable, it offers robust communication over long distances with several devices connected to the same bus. This is why it remains an essential solution for industrial automation, home automation and control systems, where stability and simplicity are essential.
Advantages of RS‑485 communication cable
- Reliable long distance transmission : Allows stable communication up to 1200m thanks to differential signal and twisted pair.
- Excellent EMC immunity : Effective shielding reduces electromagnetic interference (EMI), guaranteeing data integrity.
- Installation flexible : Flexible structure suitable for fixed installation or mobile applications in demanding industrial environments.
- Multi-device compatibility : Support for multipoint networks with multiple terminals connected on the same bus line.
- Easy to integrate : Designed to meet the requirements of PLCs, sensors, building control systems, etc.
Transport – ZMS CABLE
- The cables are packed on treated wooden towns or metal drums, With plastic film or BOPP for humidity protection.
- We offer maritime transport in 20ft or 40ft container, Depending on the control volume.
- Land transport is available for regional or local deliveries (Depending on the destinations).
- On demand, We also provide air transport for urgent orders.
- All necessary export documents are provided : commercial invoice, packing list, original certificate, documents douaniers, etc.