The RS 485 protocol is standard for sending serial data. It uses a pair of wires to send a differential signal over distances up to 4000 feet without a repeater. The differential signal makes it very robust, RS-485 is one of the most popular communications methods used in industrial applications where it’s noise immunity and long-distance capability are a perfect fit. RS-485 is capable of multi-drop communications – up to 32 nodes
RS-485 can be configured for their half or full duplex. Half duplex typically uses one pair of wires, full duplex requires two pair.
RS-485 Tech Tip: Always run a signal ground with RS-485
| Typical Data rates: |
Up to 115,200 baud |
| Max Distance: |
4000 feet |
| Cabling Requirements: |
Twisted Pair plus signal ground |
| Duplex: |
Half or Full depending on configuration |
| Multidrop: |
Up to 32 nodes |
| RS-485 Tech Support Tip: |
Always run a signal ground with RS-485 |
| Common Applications: |
Industrial Equipment, Modbus, Machine to Machine (M2M) communications |
Pros:
- Long distance
- Noise immunity
- Multidrop capable
- Used in many popular fieldbuses
Cons
- Physical layer only, no protocol specified
- Not inherently isolated – use of isolated products recommended