National Instruments NI 9423 User manual

OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9421/9423
8-Channel Sinking Digital Input Modules
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NI 9421/9423 2 ni.com
This document describes how to use the National Instruments 9421
and National Instruments 9423 and includes specifications and
terminal assignments for the NI 9421/9423. In this document, the
NI 9421 with screw terminal, NI 9421 with DSUB, and NI 9423
are referred to inclusively as the NI 9421/9423. Visit ni.com/
info and enter rdsoftwareversion to determine which
software youneed for the modules youare using. For information
about installing, configuring, and programming the system, refer to
the system documentation. Visit ni.com/info and enter
cseriesdoc for information about C Series documentation.
Note The safety guidelines and specifications in this
document are specific to the NI 9421/9423. The other
components in the system might not meet the same safety
ratings and specifications. Refer to the documentation for
each component in the system to determine the safety
ratings and specifications for the entire system. Visit
ni.com/info and enter cseriesdoc for information
about C Series documentation.

© National Instruments Corp. 3 NI 9421/9423
Safety Guidelines
Operate the NI 9421/9423 only as described in these operating
instructions.
Hot Surface This icon denotes that the component may be
hot. Touching this component may result in bodily injury.
Safety Guidelines for Hazardous Voltages
Yo ucan connect hazardous voltages to the NI 9421/9423 with
screw terminal only. Do not connect hazardous voltages to the
NI 9421 with DSUB.
If hazardous voltages are connected to the module, take the
following precautions. A hazardous voltage is a voltage greater
than 42.4 Vpk or 60 VDC to earth ground.
Caution Ensure that hazardous voltage wiring is
performed only by qualified personnel adhering to local
electrical standards.
Caution Do not mix hazardous voltage circuits and
human-accessible circuits on the same module.

NI 9421/9423 4 ni.com
Caution Make sure that devices and circuits connected to
the module are properly insulated from human contact.
Caution When module terminals are hazardous voltage
LIVE (>42.4 Vpk/60 VDC), youmust ensure that devices
and circuits connected to the module are properly
insulated from human contact. Youmust use the NI 9932
connector backshell kit to ensure that the terminals are
not accessible.
Figure 1 shows the NI 9932 connector backshell.
Note Yo ucan use the NI 9932 connector backshell only
with the NI 9421/9423 with screw terminal.

© National Instruments Corp. 5 NI 9421/9423
Figure 1. NI 9932 Connector Backshell
Safety Guidelines for Hazardous Locations
The NI 9421/9423 is suitable for use in Class I, Division 2,
Groups A, B, C, D, T4 hazardous locations; Class I, Zone 2,
AEx nC IIC T4, and Ex nC IIC T4 hazardous locations; and
nonhazardous locations only. Follow these guidelines if youare
installing the NI 9421/9423 in a potentially explosive environment.
Not following these guidelines may result in serious injury or
death.

NI 9421/9423 6 ni.com
Caution Do not disconnect I/O-side wires or connectors
unless power has been switched off or the area is known
to be nonhazardous.
Caution Do not remove modules unless power has been
switched off or the area is known to be nonhazardous.
Caution Substitution of components may impair
suitability for Class I, Division 2.
Caution For Zone 2 applications, install the system
in an enclosure rated to at least IP 54 as defined by
IEC 60529 and EN 60529.
Caution For Zone 2 applications, connected signals must
be within the following limit:
Capacitance.......................... 0.2 μF max
Special Conditions for Hazardous Locations Use in Europe
This equipment has been evaluated as Ex nC IIC T4 equipment
under DEMKO Certificate No. 03 ATEX 0324020X. Each module
is marked II 3G and is suitable for use in Zone 2 hazardous
locations, in ambient temperatures of –40 °C ≤Ta ≤70 °C. If you

© National Instruments Corp. 7 NI 9421/9423
are using the NI 9421/9423 in Gas Group IIC hazardous locations,
youmust use the device in an NI chassis that has been evaluated as
Ex nC IIC T4, EEx nC IIC T4, Ex nA IIC T4, or Ex nL IIC T4
equipment.
Special Conditions for Marine Applications
Some modules are Lloyd’s Register (LR) Type Approved for
marine applications. To verify Lloyd’s Register certification, visit
ni.com/certification and search for the LR certificate, or
look for the Lloyd’s Register mark on the module.
Caution To meet radio frequency emission requirements
for marine applications, use shielded cables and install
the system in a metal enclosure. Suppression ferrites
must be installed on power supply inputs near power
entries to modules and controllers. Power supply and
module cables must be separated on opposite sides of the
enclosure and must enter and exit through opposing
enclosure walls.

NI 9421/9423 8 ni.com
Connecting the NI 9421/9423
The NI 9421/9423 provides connections for eight digital input
channels.
Figure 2. NI 9421/9423 Terminal and Pin Assignments
DI0
DI1
DI2
DI3
DI4
DI5
DI6
DI7
NC
COM
03
47
0
1
2
3
4
5
6
7
8
9
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
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
03
47

© 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
youcan 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 Yo umust 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 ucan 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.

NI 9421/9423 10 ni.com
Connect the output of the sourcing-output device to DI on the
NI 9421/9423. Connect the common of the external device to the
COM terminal or pin. Refer to Figure 3 for an illustration of
connecting a device to the NI 9421/9423.
Figure 3. Connecting a Device to the NI 9421/9423 (3-Wire Device Shown)
NI 9421/9423
+
–
Sourcing-Output
Device
COM
DI
External
Power
Supply