© National Instruments Corp. 9 NI 9421/9423
The NI 9421/9423 with screw terminal has a 10-terminal,
detachable screw-terminal connector. The NI 9421 with DSUB has
a 25-pin DSUB connector.
Each channel of the NI 9421/9423 has a DI terminal or pin to which
you can connect voltage or current signals. The NI 9421/9423 also
has COM, a common terminal or pin that is internally connected to
the isolated ground reference of the module.
Note You must use 2-wire ferrules to create a secure
connection when connecting more than one wire to a
single terminal on the NI 9421/9423 with screw terminal.
The NI 9421/9423 has sinking inputs, meaning that when the
external device drives current or applies voltage to the DI terminal
or pin, DI provides a path to COM for the current or voltage. The
NI 9421/9423 internally limits current signals connected to DI. For
more information about input current levels, refer to the
Specifications section.
Yo u can connect 2-, 3-, and 4-wire sourcing-output devices to the
NI 9421/9423. A sourcing-output device drives current or applies
voltage to DI. An example of a sourcing-output device is an open
collector PNP.
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