RS-485 / EtherGate: Daisy Chain Practical Cable Distance

[Scott_MCN]

Greetings All,

I am looking for the practical cable distance limit of an RS-485 Daisy Chain through EtherGate.

My current understanding is that the device limit is roughly a third of the standard 32 devices (6-10), however I could not find any practical documentation on Cable Distance in real-world applications, and am sure that it will be less than 4000m - the standard for RS-485.

Regards, Scott.

[Benji]

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[abhishek_lanjul]

Hi Scott,

According to my knowledge the device limit is 32 device on paper but for practically it is recommended to use

Up to 25-30 device on single daisy chain loop without any repeater to avoid disturbance and fluctuation of data.

And if we are talking about cable distance in real time application it is 4000 feet i.e.,around 1200 m.

Regards,

Abbyshek

[Bojan]

The maximum length of the daisy chain is dependent on the baud rate of the devices.

See table below.

Typical maximum RS-485 Drive Distance

Baud Rate	150-9600	19200	38400	57600	115200
Distance (feet)	4000	3200	3000	2300	1600
Distance (meters)	1220	975	914	701	488

*Note: Based on 24 AWG twisted shielded pair, 0.026 Ohm/ft (0.085 Ohm/m), 13pF/ft(41pF/m) conductor to conductor, 22 Pf/ft (72pF/m) conductor to shield.