OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9478
16-Channel, 0–50 V, Sinking Digital Output Module
with Programmable Current Limits
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This document describes how to use the National Instruments 9478
and includes specifications and pin assignments for the NI 9478.
Vis it ni.com/info and enter rdsoftwareversion to determine
which software you need for the modules you are using. For
information about installing, configuring, and programming the
system, refer to the system documentation. Visit
and enter
cseriesdoc for information about C Series
ni.com/info
documentation.
Note The safety guidelines and specifications in this
document are specific to the NI 9478. 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.
NI 9478 Operating Instructions and Specifications 2 ni.com
Safety Guidelines
Operate the NI 9478 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 Locations
The NI 9478 is suitable for use in Class I, Division 2, Groups A, B,
C, D, T4 haza rdous locations; Class I, Zone 2, AEx nA IIC T4, and
Ex nA IIC T4 hazardous locations; and nonhazardous locations
only. Follow these guidelines if you are installing the NI 9478 in a
potentially explosive environment. Not following these guidelines
may result in serious injury or death.
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.
© National Instruments Corp. 3 NI 9478 Operating Instructions and Specifications
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, install a protection
device across the external power supply and the COM
pin. The device must prevent the external power supply
voltage from exceeding 70 V if there is a transient
overvoltage condition.
Special Conditions for Hazardous Locations Use in Europe
This equipment has been evaluated as Ex nA IIC T4 equipment
under DEMKO Certificate No. 07 ATEX 0626664X. Each module
is marked II 3G and is suitable for use in Zone 2 hazardous
locations. If you are using the NI 9478 in Gas Group IIC hazardous
locations or in ambient temperatures of –40 °C ≤ Ta ≤ 70 °C, you
must use the device in an NI chassis that has been evaluated as
EEx nC IIC T4, Ex nA IIC T4, or Ex nL IIC T4 equipment.
NI 9478 Operating Instructions and Specifications 4 ni.com
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.
© National Instruments Corp. 5 NI 9478 Operating Instructions and Specifications
Connecting the NI 9478
The NI 9478 has a 37-pin DSUB connector that provides
connections for the 16 digital output channels.
1
COM
COM
COM
COM
COM
COM
COM
COM
Vsup
Vsup
COM
COM
COM
COM
COM
COM
COM
COM
Figure 1. NI 9478 Pin Assignments
NI 9478 Operating Instructions and Specifications 6 ni.com
DO0
20
2
DO1
21
3
DO2
22
4
DO3
23
5
DO4
24
6
DO5
25
7
DO6
26
8
DO7
27
9
Vsup
28
10
Vsup
29
11
DO8
30
12
DO9
31
13
DO10
32
14
DO11
33
15
DO12
34
16
DO13
35
17
DO14
36
18
DO15
37
19
NC
Each channel of the NI 9478 has a DO pin to which you can
connect the load you want to control. Each channel also has a COM
pin. National Instruments recommends you provide independent
COM wiring for each channel to minimize current flow in the
COM wiring. The COM pins are all connected together internally.
Yo u must connect an external power supply to the NI 9478. This
power supply provides the current for the devices you connect to
the module. Connect the positive lead of the power supply to V
sup
and the negative lead of the power supply to COM.
Caution Do not remove or insert modules if the external
power supply connected to the V
pin is powered on.
sup
The NI 9478 has current sinking outputs, meaning the DO pin is
driven to COM when the channel is turned on.
Yo u can directly connect the NI 9478 to a variety of industrial
devices such as solenoids, motors, actuators, relays, and lamps.
Make sure the devices you connect to the NI 9478 are compatible
with the output specifications of the module. Refer to the
Specifications section for more information about the output
specifications.
© National Instruments Corp. 7 NI 9478 Operating Instructions and Specifications
Connect the device to DO and the positive lead of the power
supply. Refer to Figure 2 for an illustration of how to connect
a device to the NI 9478.
V
sup
Cable
Clamp
NI 9478
DO
COM
Device
External
+
Powe r
–
Supply
Figure 2. Connecting a Device to the NI 9478
Yo u must connect the V
pin to the power supply to enable a
sup
weak cable clamping diode that protects the module from cable
inductance flyback. This flyback voltage results from small
amounts of energy stored in the inductance of the cabling. Refer
to the Using Long Cables section for more information about
protection from cable inductance flyback. You still must install an
external flyback diode when switching inductive loads. Refer to the
Protecting the Module from Flyback Voltages section for more
information about installing a flyback diode.
NI 9478 Operating Instructions and Specifications 8 ni.com
Protecting the Module from Flyback Voltages
If the module is switching an inductive or energy-storing device
such as a solenoid, motor, or relay, and the device does not have
flyback protection, install an external flyback diode as shown in
Figure 3. Refer to the Using Long Cables section for more
information about protection from cable inductance flyback.
V
sup
Cable
Clamp
NI 9478
Figure 3. Connecting a Flyback Diode to the NI 9478
© National Instruments Corp. 9 NI 9478 Operating Instructions and Specifications
DO
COM
Device
External
+
Power
–
Supply
Using Long Cables
The inductance of the cabling that connects the NI 9478, the loads,
and the external supply stores up energy when a channel is on and
passing current through the cables. Each time a channel is turned
off, the energy stored in the cables is released as flyback voltage
and dissipates as heat in the NI 9478. The total power dissipated in
the module increases with higher switching frequencies, higher
currents, and longer cable lengths. The cable length is the total
distance from the digital output pin of the NI 9478 channel,
through the load, through the external power supply, and back
to the COM pin, as shown in Figure 4.
V
sup
Load
Cable
Clamp
DO
Cable
Length
NI 9478
COM
Figure 4. Cable Length of the NI 9478
NI 9478 Operating Instructions and Specifications 10 ni.com
External
+
Power
–
Supply
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