FAQ#073 - Which is the maximum number of digitized sensors (RS-485, Modbus), the maximum number of chains and the maximum length of cable in a RS-485 network?

All the SISGEO digital sensors (IPIs, Tilt-meters, RDSs, H-Level etc..) use the serial RS-485 communication protocol.

1. The maximum number of digital sensors in a RS-485 network are 250 (theoretical)
2. The maximum number of digital sensors chains that is possible to connect to Modbus master unit (as OMNIAlog or miniOMNIAlog) are 4.
3. About the maximum distance (with digital sensors configured in "Always On") :

• a. max. 250m (in one chain) from the 1st digital sensor to the last sensor (physical cable length) and:
  - 50 digital sensors for Tiltmeters and H-Level
  - 70 digital sensors for RDS, BH-Profile and IPI
• b. max. 1000m from the 1st digital sensor to Modbus master unit (as OMNIAlog or miniOMNIAlog) with a suitable cable size (i.e. cable 0WE606IPDZH)

NOTE: The sum of 3A and 3B lengths can’t exceed 1000m. The compliance of points 3A and 3B, avoids the excessive voltage drop on the RS-485 line and guarantees the correct RS-485 network operation