Signal Loss and EMI Noise Keep Slowing Down Your Fieldbus Network?
In process plants, refineries, and heavy manufacturing facilities, unreliable cable is the hidden cause behind intermittent RS485 communication errors, dropped serial packets, and costly unplanned downtime. Standard unshielded or poorly rated twisted pair cable degrades fast in high-EMI environments — near VFDs, welders, and motor starters — corrupting your fieldbus signal before it reaches the controller.The Belden 9843 is engineered to eliminate that problem.
What Is the Belden 9843 Cable?
The Belden 9843 is a three-pair shielded twisted pair (TP-STP) cable specifically designed for balanced differential signal transmission in RS485 fieldbus, serial port (UART/RS232-RS485 conversion), and industrial LAN applications. Each pair is individually twisted and collectively shielded with a tinned copper braid, delivering consistent 120Ω characteristic impedance across the full cable run. This makes it a direct-fit replacement in Profibus, Modbus RTU, DH-485, and other multi-drop serial bus topologies where signal integrity over distance matters.
Core Specifications
| Parameter | Value |
|---|---|
| Conductor | 24 AWG stranded tinned copper |
| Pairs | 3 twisted pairs |
| Shield | Tinned copper braid, 85% coverage |
| Impedance | 120Ω ± 10% |
| Capacitance | 15 pF/ft (49 pF/m) typical |
| Voltage Rating | 300V |
| Temperature Range | -20°C to +75°C (continuous) |
| Jacket | PVC / LSZH options available |
| Bend Radius | 4× cable OD (minimum) |
| Standards | RoHS, UL/CSA Type CM/CMP |
Why Plants Choose Belden 9843 Over Generic Cable
1. Consistent 120Ω Impedance Prevents Signal ReflectionsRS485 fieldbus relies on proper termination matching. The Belden 9843 holds 120Ω impedance within tolerance across temperature swings, reducing reflections at junction boxes and connector transitions — a common failure point in long daisy-chain runs.2. Braid Shield Blocks EMI in Harsh Electrical EnvironmentsIn facilities with variable frequency drives, switchgear, or arc welders, induced noise on unshielded pairs causes bit errors and retransmissions. The 85% tinned copper braid provides >30dB shielding effectiveness, keeping your serial data clean even in 480V panels.3. Three-Pair Layout Supports Multi-Protocol InstallsOne cable run carries RS485 data, spare pair for secondary signal or power-over-data applications, and a dedicated ground pair. This reduces conduit fill and pull count — critical when re-cabling existing plant infrastructure.4. Tinned Copper Resists Corrosion in Wet or Chemical ZonesUnlike bare copper conductors, the tinned construction on the Belden 9843 resists oxidation in humid process areas, chemical plants, and outdoor cable tray installations, extending service life without premature failure.
Suitable Industries and Applications
- Oil & Gas / Petrochemical — RTU-to-SCADA RS485 links, DCS fieldbus trunk cables
- Water & Wastewater — Pump station serial communication, SCADA remote I/O
- Manufacturing / Automotive — PLC-to-drive Modbus RTU, robot cell serial networks
- Power Generation — Substation IEC 61850 serial backplane, relay panel wiring
- Mining & Heavy Industry — Long-run fieldbus in high-vibration, high-EMI conveyor systems
Typical installation: cable tray in control rooms, direct burial in outdoor plant perimeters, conduit runs inside motor control centers.
Get the Right Cable for Your Installation — Talk to Us
We stock the Belden 9843 in standard cuts and can supply custom lengths with your choice of jacket material, connector terminations (DB9, M12, open wire), and pull-string configurations. Need a cable assembly for a specific fieldbus topology or a quantity quote for a plant turnaround? Send us your spec sheet or drawing — our applications team responds within one business day.Request a quote for Belden 9843 today.