RS485 speed vs distance

murali kandasamy

Hi,

I want to know what is the maximum practical data rate possible using RS485 for a distance of 300m. Are there any calculators/ references which mention the practical achievable limits?

over 11 years ago

0 Avi Chami1 over 11 years ago

Mastermind 7395 points

http://www.weidmuller.ca/system/files/webfm/downloads/pdfs/literature/SIP02_991635_RS-485_Primer.pdf

0 murali kandasamy over 11 years ago in reply to Avi Chami1

Intellectual 350 points

Thank you for the reference. The document specifies a conservative speed of 300kbps over 300m cable. Can this speed be increased? Maxim MAX3291/MAX3292 specifies that pre-emphasis increases the speed/distance limitation. Is it possible to attain 700kbps over 300m?

0 Avi Chami1 over 11 years ago in reply to murali kandasamy

Mastermind 7395 points

You may also want to check this application note

http://www.ti.com/lit/an/slla169/slla169.pdf

0 Thomas Kugelstadt over 11 years ago

TI__Mastermind 28265 points

Hello, please find below two charts for cable-length vs data-rate for RS-485. The upper chart gives distance in feet, the lower one in meters. Regards, Thomas

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RS485 speed vs distance