{"id":2522,"date":"2026-09-16T11:54:50","date_gmt":"2026-09-16T03:54:50","guid":{"rendered":"https:\/\/www.syycable.com\/?p=2522"},"modified":"2026-09-17T12:20:05","modified_gmt":"2026-09-17T04:20:05","slug":"rs485-vs-rs232-vs-rs422-industrial-guide","status":"publish","type":"post","link":"https:\/\/www.syycable.com\/zh\/rs485-vs-rs232-vs-rs422-industrial-guide\/","title":{"rendered":"RS485 vs RS232 vs RS422: Wiring, Termination & Distance Limits for Industrial Networks"},"content":{"rendered":"

Three Serial Standards, Three Jobs<\/h2>\n

RS485 vs RS232 vs RS422 is the serial-standard choice that decides whether an industrial bus stays up or drops out. RS232, RS485 and RS422 are not interchangeable. Picking wrong causes the dropouts engineers blame on “bad cable.” For the full industrial serial cable<\/a> range\u2014including USB-to-serial converters<\/a>\u2014start with the topology.<\/p>\n

\"USB<\/figure>\n

For the electrical standard, see Wikipedia: RS-485 (EIA-485)<\/a>.<\/p>\n

Comparison at a Glance<\/h2>\n\n\n\n\n\n
Std<\/th>\nTopology<\/th>\nMax distance<\/th>\nNoise immunity<\/th>\n<\/tr>\n
RS232<\/td>\nPoint-to-point<\/td>\n~15 m<\/td>\nLow<\/td>\n<\/tr>\n
RS422<\/td>\n1 driver, multi-drop<\/td>\n~1200 m<\/td>\nHigh (diff)<\/td>\n<\/tr>\n
RS485<\/td>\nMulti-drop, multi-master<\/td>\n~1200 m<\/td>\nHigh (diff)<\/td>\n<\/tr>\n<\/table>\n

The RS485 Termination Rule<\/h2>\n

RS485 runs over ~50 m at high baud need a 120 \u03a9 termination resistor at each end of the bus. Missing it = reflections = intermittent CRC errors. Spec it:<\/strong> ask whether the device or the cable supplies termination.<\/p>\n

Why RS232 Still Ships<\/h2>\n

For a single PLC-to-HMI link under 15 m, RS232 is simple and ubiquitous. Don’t force RS485 where point-to-point is enough.<\/p>\n

The 3 Wiring Mistakes<\/h2>\n