Modbus RTU Transmission Speed

Hello Engineers,
i'm recently working on designing a Modbus RTU network over RS485,
i have 13 slaves, the distance between them is 40m, the totale distance is 650m, i will use a twisted paire cable with 22 AWG and 120Ω of characteristic impedance.
I want to know how to calculate the transmission speed of the network.
 
You can calculate all you want, but the key factor is slave wake-up and response time, so in the end, the throughput rate is empirical - it is what it is at a given baud rate. And it assumes 100% functionality - one slave going off line invokes the master's time-out, which extends the total throughput time.

These classic oldie threads have covered the topic in the past

http://www.control.com/thread/1397486168#1397486168

https://control.com/forums/threads/rs485-timing-considerations.952/#post-52329

Slaves from different manufacturers can have different responses.
 
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