NI 9425 Operating Instructions and Specifications
8
ni.com
Each channel has a DI pin to which yo
u
can connect a digital inp
u
t
signal. The NI 9425 has fo
u
r common pins, COM, that are
internally connected to the isolated reference of the mod
u
le.
The NI 9425 has sinking inp
u
ts, meaning that when the device
drives a c
u
rrent or applies a voltage to the DI pin, the pin provides
a path to COM for the c
u
rrent or voltage. The NI 9425 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
section.
Yo
u
can connect 2-, 3-, and 4-wire so
u
rcing-o
u
tp
u
t
devices to
the NI 9425. A so
u
rcing-o
u
tp
u
t device drives c
u
rrent or applies
voltage to the DI pin. An example of a so
u
rcing-o
u
tp
u
t device is an
open collector PNP.
Connect the so
u
rcing-o
u
tp
u
t device to the DI pin on the NI 9425.
Connect the common of the external device to the COM pin. Refer
to Fig
u
re 2 for an ill
u
stration of connecting a device to the
NI 9425.
