National Instruments NI 9871 User manual
OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9871
4-Port, RS485/RS422 Serial Module
NI 9871 Operating Instructions 2 ni.com
This document describes how to use the National Instruments 9871
and includes specifications and pin assignments for the NI 9871.
Visit 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 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 9871. 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.
Safety Guidelines
Operate the NI 9871 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.
© National Instruments Corp. 3 NI 9871 Operating Instructions
Safety Guidelines for Hazardous Locations
The NI 9871 is suitable for use in Class I, Division 2, Groups A, B,
C, D, T4 hazardous locations; Class I, Zone 2, AEx nA II T4 and
Ex nA II T4 hazardous locations; and nonhazardous locations only.
Follow these guidelines if you are installing the NI 9871 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.
Caution Substitution of components may impair
suitability for Class I, Division 2.
Caution For Zone 2 applications, install the
CompactRIO system in an enclosure rated to at least
IP 54 as defined by IEC 60529 and EN 60529.
NI 9871 Operating Instructions 4 ni.com
Caution For Zone 2 applications, install a protection
device between the RS485/RS422 signal cables and the
NI 9871 RJ-50 jacks (ports 1–4). The device must
prevent the RS485/RS422 signal-to-signal or
signal-to-COM voltage from exceeding 23 V if there is a
transient overvoltage condition.
Caution For Zone 2 applications, install a protection
device between the external power supply and the
NI 9871 Vsup and COM pins. The device must prevent the
Vsup-to-COM voltage from exceeding 39 V if there is a
transient overvoltage condition.
Special Conditions for Hazardous Locations 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 9871 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 or controller that has been
evaluated as EEx nC IIC T4, Ex nA IIC T4, or Ex nL IIC T4
equipment.
© National Instruments Corp. 5 NI 9871 Operating Instructions
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 9871 Operating Instructions 6 ni.com
Wiring the NI 9871
The NI 9871 has four RJ-50 receptacles that provide connections
for four RS485/RS422 devices.
Table 1. RS485/RS422 Port Pinout
RJ-50 Pin Signal Name*
1No Connect
2TXD–
3TXD+
4RTS–
5CTS–
6RXD–
7RXD+
8RTS+
9CTS+
10 GND
* These signals are shared by all four RJ-50 connectors on the NI 9871.
RJ50 Jack
NC
TXD–
TXD+
RTS–
CTS–
RXD–
RXD+
RTS+
CTS+
COM
1
2
3
4
5
6
7
8
9
10
© National Instruments Corp. 7 NI 9871 Operating Instructions
The cables included with your kit convert the RJ-50 pinout to the
standard NI pinout, as shown in Table 2.
Table 2. Pin Assignments for RS485/RS422 DB-9 Male Connector
Connector Pin Signal
1GND
2CTS+
3RTS+
4RXD+
5RXD–
6CTS–
7RTS–
8TXD+
9TXD–
6
7
8
9
1
2
3
4
5
NI 9871 Operating Instructions 8 ni.com
You must connect an external power supply to the NI 9871.
This power supply provides the power for the RS485/RS422
transceivers on the module. You can use the included female
four-position pigtail to connect to an external voltage source.
Figure 1 lists the connections between an external voltage source
(of +8 V to +28 V) and the NI 9871.
Figure 1. Four-Position External Power Connector
1V
SUP 2V
SUP 3COM 4COM
1
3
4
2
© National Instruments Corp. 9 NI 9871 Operating Instructions
Figure 2 shows the method of power connection to the NI 9871
module. Attach an isolated power supply to the Vsup and COM
terminals using the included pigtail.
Figure 2. Powering the NI 9871 from an Isolated Power Source
Figure 3 shows how to use the optional y-adapter (available at
ni.com/serial) to connect power to more than one module
using the same power source. One y-adapter is needed for each
Red (+)
Black (–)
NI P/N 198159-XX:
Female Microfit
Pigtail
V+
V–
Any 8 - 28 V
Isolated
Power Supply
NI 9871 Operating Instructions 10 ni.com
additional module. Ensure that the power supply can handle
maximum power requirements for all modules connected.
Caution All connections must be made before power is
applied.
Figure 3. Powering Multiple Modules from a Single Power Supply
Red (+)
Black (–)
NI P/N 198303-XX:
Male Microfit
Y-Adapter
NI P/N 198159-XX:
Female Microfit
Pigtail
V+
V–
Any 8 - 28 V
Isolated
Power Supply
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