Table of Contents
Advertisement
3.2 Safety considerations
3.3 Examples for connecting the SDM-SIO1A to other equipment
3.3.1 RS-485/RS-422 Full duplex, one to one connection example
+12V
G
C1
C2
C3
RG
G
RTS/TD+
TX/TD-
RX/RD+
CTS/RD-
The SDM-SIO1A is considered to be a component of a measurement system that is
installed in an enclosure and wired up in accordance with this manual. Due to
space considerations full details of the maximum ratings of the connections are not
given on the device. Instead the user should study this manual and in particular
Section 2.2.2 to determine the maximum voltages that are applicable to any
terminal before starting an installation.
The RS-485 0V ground reference connection may be needed to ensure all units are
referenced to a common ground voltage. This is more often needed with long cable
runs.
It is advisable to check the difference in ground potential with some caution before
connecting any wires, to ensure the potential differences are reasonably close and
excessive current will not flow between the two ground wires. There is a current
limiting resistor fitted in the RG line in the SDM-SIO1A, but this will not be
adequate in the event of a serious ground fault, e.g. the ground references being
240 V apart, due to faulty AC wiring. If a large potential difference is found please
seek the advice of a qualified electrician before continuing with the installation.
Optional 100R resistors
To logger
R
R
RS485 0V can be connected
straight to 0V but, this is not
recommended for long wire
lengths.
* Note connection order
First RS485
RS485 0V
equipment
RS485 TD+
with
RS485 TD-
termination
RS485 RD+
resistors
RS485 RD-
User Guide
9
Advertisement
Table of Contents
