SonTek/YSI
ADVField/Hydra Operation Manual (September 1, 2001) 107
Appendix 3. Multiple ADVField/Hydra Operation using RS485
This appendix describes the simultaneous operation of multiple ADVFields/Hydras in RS485
mode. Each system must be hardwired at the factory to use RS485 protocol.
A3.1. Overview
RS485 serial communication protocol allows multiple systems to be controlled from a single
communication line.
•
RS485 uses the same electrical communication protocol as RS422, allowing operation over
total cable lengths up to 1500 m (4500 feet).
•
A RS422/RS232 converter is used to connect the RS485 ADVField/Hydra systems to a stan-
dard PC serial port.
•
Each ADVField/Hydra is configured with a unique system address.
•
All communication is prefaced with a system address; each ADVField/Hydra responds only
to commands directed to its specific address.
•
Operation and data collection for all systems is controlled from a single PC. Data from each
system is stored in a separate data file on the PC.
•
Multiple systems are “daisy-chained” together as shown in Figure 25.
Figure 25 – RS485 Overview
Primary
DAQ computer
Secondary 1
Secondary N
. . .
422/232
converter
Splitter cable B
Splitter cable B
Converter
cable C
Power to
Converter
DB 9
DB 9
DB 25
Splitter cable B
DB 9
Primary cable A
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