©
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
yo
u
can connect voltage or c
u
rrent signals. The NI 9421/9423 also
has COM, a common terminal or pin that is internally connected to
the isolated gro
u
nd reference of the mod
u
le.
Note
Yo
u
m
u
st
u
se 2-wire ferr
u
les to create a sec
u
re
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 inp
u
ts, meaning that when the
external device drives c
u
rrent or applies voltage to the DI terminal
or pin, DI provides a path to COM for the c
u
rrent or voltage. The
NI 9421/9423 internally limits c
u
rrent signals connected to DI. For
more information abo
u
t inp
u
t c
u
rrent levels, refer to the
Specifications
section.
Yo
u
can connect 2-, 3-, and 4-wire so
u
rcing-o
u
tp
u
t devices to the
NI 9421/9423. A so
u
rcing-o
u
tp
u
t device drives c
u
rrent or applies
voltage to DI. An example of a so
u
rcing-o
u
tp
u
t device is an open
collector PNP.
