National Instruments NI 9411 Operating Instructions And Specifications page 8

Each channel has two pins, DIa and DIb, to which you can
connect digital input signals. The DSUB connector also provides
two connections for supplying power to an external device and
a connection for common. The NI 9411 also has a 2-terminal
screw-terminal connector that provides connections for an external
power supply.
If you do not have a 5 V power supply to directly power the
external device or if you want to simplify wiring, you can connect
an external power supply to the V
NI 9411 screw-terminal connector, and connect the external device
to one of the 5 V
you do not need to connect a power supply to the NI 9411 or
connect the +5 V
Specifications
supply specifications.
Note
connection when connecting more than one wire to a
single terminal on the NI 9411 screw-terminal connector.
Connecting Differential Devices to the NI 9411
You can connect differential devices to the NI 9411. Connect the
device to the DIa and DIb pins on the NI 9411. The NI 9411
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and COM terminals on the
sup
pins. If the external device is already powered,
out
pin to the external device. Refer to the
out
section for information about the external power
You must use 2-wire ferrules to create a secure
7 NI 9411 Operating Instructions and Specifications