1. Introduction
The SDM-SIO2R Serial Input/Output Module is designed to allow expansion of the number of
serial ports available on a data logger for communicating with intelligent sensors or driving
external displays. It also has built-in power pass-through capabilities. Each SDM-SIO2R provides
two separate communication channels and four different switched voltages.
Figure 1-1. SDM-SIO2R
2. Precautions
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WARNING: Ensure that the 12V power supply for the module is switched off when
connecting the power and ground wires to the SDM-SIO2R. When making connections to
a data logger, always ensure power to the data logger is switched off and connect the
ground (G) wire first.
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WARNING: 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
SDM-SIO2R Serial Input/Output Module with Switched Sensor Power
1
