National Instruments NI USB-9421 用户手册
NI USB-9421 User Guide and Specifications
12
ni.com
Figure 7. Pin Assignments
Connecting Devices to the NI USB-9421
The NI USB-9421 has sinking inputs, meaning that when current goes
through or voltage is applied to the DI terminal or pin, DI provides a path
to ground for the current or voltage. The NI USB-9421 internally limits
current signals connected to DI. For more information about input current
protection, refer to the
through or voltage is applied to the DI terminal or pin, DI provides a path
to ground for the current or voltage. The NI USB-9421 internally limits
current signals connected to DI. For more information about input current
protection, refer to the
section.
You can connect 2-, 3-, and 4-wire sourcing-output devices to the
NI USB-9421. A sourcing-output device drives current or applies voltage
to DI. An example of a sourcing-output device is a PNP open collector.
NI USB-9421. A sourcing-output device drives current or applies voltage
to DI. An example of a sourcing-output device is a PNP open collector.
Connect the output of the sourcing-output device to DI on the
NI USB-9421. Connect the common of the external device to the COM
terminal or pin. Figure 8 shows a possible configuration.
NI USB-9421. Connect the common of the external device to the COM
terminal or pin. Figure 8 shows a possible configuration.
COM
NC
COM
COM
NC
COM
COM
NC
COM
COM
NC
COM
COM
NC
COM
COM
NC
COM
COM
NC
COM
COM
NC
COM
COM
DI0
NC
DI1
DI2
NC
DI3
DI4
NC
DI5
DI6
NC
DI7
NC
DI1
DI2
NC
DI3
DI4
NC
DI5
DI6
NC
DI7
1
2
3
4
5
6
7
8
9
2
3
4
5
6
7
8
9
10
11
12
13
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
15
16
17
18
19
20
21
22
23
24
25
0
3
4
7