YSI IQ SensorNet MIQ/A-MOD Module - Manual (Page 21)

MIQ/(A-)MOD Interface for the Modbus RTU
21 ba76021e01 01/2012
3.4 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?
 Have the devices been restarted after changing the bus address,
baud rate or parity (switched off and then on again)?
 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?