Wiring Examples For Connecting The Sdm-Sio1A - Campbell SDM-SI01A Product Manual

When connecting multiple SDM devices to a data logger, the SDM connections can either be all
connected by separate wires back to the data logger terminals or, as is common if the SDM
devices are mounted in a row in an enclosure, jumper wires can be used to daisy-chain the same
terminals on each interface together (including power and ground) with one set of wires running
back to the data logger. It is important to keep the total length of SDM wiring as short as
possible.
The connection of the wires to the remote serial device will vary with type of device and method
of communication. It is necessary to work out the best mode of operation of the serial device,
taking into consideration issues such as power consumption, cable lengths (RS-485 being better
than RS-232 for long cables), synchronization of data collection, etc.
NOTE:
If possible, use screened cable for connecting the SDM-SIO1A to remote sensors or devices.
Check the manual of the device for details on where to connect the screen for maximum
effectiveness.
RS-422 mode is functionally the same as RS-485 mode except the connection is limited to a
point-to-point system. Connections and programming for
RS-422 are otherwise identical to full-duplex RS-485.
When operating in RS-232 mode, the SDM-SIO1A also supports hardware handshaking.

Wiring examples for connecting the SDM-SIO1A

connection schemes for the serial devices. Further discussion of different modes of operation is
given in Operation (p. 24).
6.2.1 Wiring examples for connecting the SDM-SIO1A
The exact method of wiring the SDM-SIO1A varies with the type of device it is going to exchange
data with. The variables include the type of interface used (RS-232, RS-485, or RS-422), whether
handshaking is used, whether the connection is full or half duplex, and whether termination
resistors are used (RS-485 and RS-422 only).
Typical wiring for the most common configurations are given as examples in the following
subsections.
(p. 13) provides examples of different
SDM-SIO1A and SDM-SIO4A Serial Input/Output Modules 13