YSI DIQ/S 182-MOD System 182 - Manual (Page 113)

System 182 Modbus connection
7 - 1 ba76025e01 02/2012
7 Modbus connection
Note
Further instructions for the installation and operation of a Modbus
network are given in the Internet under www.modbus.org.
7.1 Modbus checklist
The following checklist supports you when planning, projecting and
installing a Modbus plant with the IQ S
ENSOR N ET . For smooth
operation, you should be able to answer all questions with "Yes".
 Is the [bus system] (bus segment) installed without branch lines?
 Was the correct Modbus cable used (cord type A according to
EN 50170)?
 Are the poles of the signal lines A line and B line correctly connected
at all bus connections?
 Is it guaranteed that there is no short-circuit between A line, B line
and cable shielding?
 Is the shielding installed free of interruptions?
 Are the guidelines for shielding and grounding being observed, and
doesn't any unallowed potential equalization current flow
via the shielding?
 Is the maximum cable length (per bus segment) observed for the
corresponding baud rate?
 Do all devices support the required baud rate?
 Are exactly two terminators switched on at the ends of the [bus
system] (bus segment)?
 Are the terminators supplied with voltage so the following applies:
U
B line
- U
A line
> + 500 mV?
 Do all devices have individual bus addresses?
 After changing the bus address, have the devices been restarted
(switched off and on again)?
Note: The DIQ/S 182-MOD does not have to be restarted.
 Do the addresses projected in the master correspond to the actual
addresses?
 After commissioning:
Do all devices signal error-free behavior?
 Is it guaranteed that the Modbus master has consistent access
to the 16 byte sensor data structure?