Cable Specification for Modbus-RTU/RS-485


Thread Starter

Ivan R. Leite

I need urgently, please!
I need modbus-rtu cable electrical stand RS-485:
1 - What the best cable specification for this case?
2 - The distance is small < 50m non necessary the resistor, ok?
3 - What the stand color for modbus cables?

Curt Wuollet

Just Google Belden rs485, but really, many people carry RS485 wire. I've used a couple miles from Automation Direct with no complaints. For a spec just get cable for RS485.

No, it's never good to omit termination. For short distances it'll work, but because of standing waves some lengths will work and some won't, for maybe 5 cents, it will eliminate a variable and give you better signals. Do yourself a favor and look up the 10 ways to make your RS485 network bulletproof. Done right, it is superbly reliable. Done haphazardly you'll have random weirdness that's really hard to figure out. I don't understand why so many people have a problem with a 5 cent termination resistor.

The cables I've seen most often use red and green or blue and white. And the spendy purple cable is just RS485 cable too. You can get jackets in almost any color.