Up to 8 SDM-SIO2Rs can be connected to a single data logger via the SDM port, allowing the
user to connect 15 different items of equipment to their data logger with ease, in addition to any
connections made to the data logger built-in serial ports. (Note that when using 8 SDM-SIO2Rs,
only one-half of one of the SDM-SIO2Rs will be active. SDM allows for only 15 addresses, and
each SDM-SIO2R requires two addresses. Any of the eight devices can be the one that is only
partially active.) Only one SDM-SIO2R needs to be wired to power and SDM communications on
the data logger. A din rail bus system is used to distribute the pass-through power and
communication to the other devices.
The SDM-SIO2R can also be used in “talk-through” mode to allow a user to talk, via a terminal
program, to a sensor connected to the SDM-SIO2R for test and diagnostic purposes. Please refer
to the data logger manual for further details.
The SDM-SIO2R has four terminals that allow the user to control voltage on or off:
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Sensor 1: 12V
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Sensor 1: V+
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Sensor 2: 12V
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Sensor 2: V+
Voltage to these terminals is controlled through the CRBasic program. See
NOTE:
The SDM-SIO2R is not a power supply. This device must be wired to a power supply that is
capable of delivering the needed voltage and current. The SDM-SIO2R can be thought of as a
pass-through switched voltage device for ease of wiring.
LEDs are used to indicate the presence of power at these terminals:
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If the LED is illuminated, there is voltage at the terminal and the sensor should be receiving
power.
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If the LED is dark, there is no voltage at the indicated terminal.
NOTE:
For proper LED indication the 12V side of the SDM-SIO2R must be powered. If 12V is not
powered, there may be voltage at V+ out even though the LED indicator is dark.
SDM-SIO2R Serial Input/Output Module with Switched Sensor Power
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