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 your system may not meet the same safety
ratings and specifications. Refer to the documentation for
each component in your system to determine the safety
ratings and specifications for the entire system.

© National Instruments 3 NI 9871 Operating Instructions
Safety Guidelines
Caution Do not operate the NI 9871 in a manner not
specified in the user manual or operating instructions.
Product misuse can result in a hazard. You can
compromise the safety protection built into the product if
the product is damaged in any way. If the product is
damaged, return it to National Instruments for repair.
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 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.

NI 9871 Operating Instructions 4 ni.com
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.
Caution For Zone 2 applications, install a protection
device between the RS232 signal cables and the NI 9871
RJ-50 jacks (ports 1–4). The device must prevent the
RS232 signal-to-signal or signal-to-COM voltage from
exceeding 35 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.

© National Instruments 5 NI 9871 Operating Instructions
Special Conditions for Safe 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.
Special Guidelines for Marine Applications
Some modules are Lloyd’s Register (LR) Type Approved for
marine (shipboard) applications. To verify Lloyd’s Register
certification for a module, visit ni.com/certification and
search for the LR certificate, or look for the Lloyd’s Register mark
on the product label.
Caution In order to meet the EMC requirements for
marine applications, install the module in a shielded
enclosure with shielded and/or filtered power and
input/output ports. In addition, take precautions when
designing, selecting, and installing measurement probes
and cables to ensure that the desired EMC performance is
attained.

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 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.
Caution To ensure the specified EMC performance, do not
connect the power input to a d.c. mains supply or to any
supply requiring a connecting cable longer than 30 m
(100 ft.). A d.c. mains supply is a local d.c. electricity supply
network in the infrastructure of a certain site or building.

© National Instruments 9 NI 9871 Operating Instructions
Figure 1. Four-Position External Power Connector
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.
1V
SUP 2V SUP 3COM 4COM
1
3
4
2

NI 9871 Operating Instructions 10 ni.com
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
additional module. Ensure that the power supply can handle
maximum power requirements for all modules connected.
Red (+)
Black (–)
NI P/N 198159-XX:
Female Microfit
Pigtail
V+
V–
Any 8 - 28 V
Isolated
Power Supply