National Instruments SCXI -1122 User manual

© Copyright 1993, 1999 National Instruments Corporation.
All Rights Reserved.
User Manual
Sixteen-Channel Isolated Transducer Multiplexer Module for Signal
Conditioning
September 1999 Edition
Part Number 320516B-01
SCXI -1122
TM

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Warranty
The SCXI-1122 is warranted against defects inmaterials and workmanshipfora period ofone yearfromthe date of
shipment, as evidenced by receipts or other documentation. National Instruments will, at its option, repair or replace
equipment that provesto be defective during the warranty period. This warranty includes parts and labor.
A Return Material Authorization (RMA) number must be obtained from the factory and clearly marked on the
outside of thepackage before any equipment will be accepted for warranty work. National Instruments will pay the
shipping costs of returning to the owner parts which are covered by warranty.
National Instruments believesthat the information in this document is accurate.The document has been carefully
reviewed fortechnical accuracy. In theevent that technical or typographical errors exist,National Instruments
reserves the right to makechangesto subsequent editions of this document without prior notice to holders of this
edition. Thereader should consult National Instruments if errors are suspected. In no event shall National
Instruments be liable for any damages arising out of orrelated to this document or the information contained in it.
EXCEPT AS SPECIFIED HEREIN, NATIONALINSTRUMENTS MAKESNO WARRANTIES, EXPRESSOR IMPLIED, AND
SPECIFICALLY DISCLAIMS ANYWARRANTY OF MERCHANTABILITY OR FITNESS FOR APARTICULAR PURPOSE.
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negligence. Anyaction against National Instruments must be brought within one year after the cause of action
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Product and company namesmentioned herein are trademarks or trade names oftheir respective companies.

WARNING REGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS
(1) NATIONAL INSTRUMENTS PRODUCTS ARE NOT DESIGNED WITH COMPONENTS AND TESTING
FOR A LEVEL OF RELIABILITY SUITABLE FOR USE IN OR IN CONNECTION WITH SURGICAL
IMPLANTS OR AS CRITICAL COMPONENTS IN ANY LIFE SUPPORT SYSTEMS WHOSE FAILURE TO
PERFORM CAN REASONABLY BE EXPECTED TO CAUSE SIGNIFICANT INJURY TO A HUMAN.
(2) IN ANY APPLICATION, INCLUDING THE ABOVE, RELIABILITY OF OPERATION OF THE
SOFTWARE PRODUCTS CAN BE IMPAIRED BY ADVERSE FACTORS, INCLUDING BUT NOT LIMITED
TO FLUCTUATIONS IN ELECTRICAL POWER SUPPLY, COMPUTER HARDWARE MALFUNCTIONS,
COMPUTER OPERATING SYSTEM SOFTWARE FITNESS, FITNESS OF COMPILERS AND
DEVELOPMENT SOFTWARE USED TO DEVELOP AN APPLICATION, INSTALLATION ERRORS,
SOFTWARE AND HARDWARE COMPATIBILITY PROBLEMS, MALFUNCTIONS OR FAILURES OF
ELECTRONIC MONITORING OR CONTROL DEVICES, TRANSIENT FAILURES OF ELECTRONIC
SYSTEMS (HARDWARE AND/OR SOFTWARE), UNANTICIPATED USES OR MISUSES, OR ERRORS ON
THE PART OF THE USER OR APPLICATIONS DESIGNER (ADVERSE FACTORS SUCH AS THESE ARE
HEREAFTER COLLECTIVELY TERMED “SYSTEM FAILURES”). ANY APPLICATION WHERE A
SYSTEM FAILURE WOULD CREATE A RISK OF HARM TO PROPERTY OR PERSONS (INCLUDING THE
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ELECTRONIC SYSTEM DUE TO THE RISK OF SYSTEM FAILURE. TO AVOID DAMAGE, INJURY, OR
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PROTECT AGAINST SYSTEM FAILURES, INCLUDING BUT NOT LIMITED TO BACK-UP OR SHUT
DOWN MECHANISMS. BECAUSE EACH END-USER SYSTEM IS CUSTOMIZED AND DIFFERS FROM
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DESIGNER MAY USE NATIONAL INSTRUMENTS PRODUCTS IN COMBINATION WITH OTHER
PRODUCTS IN A MANNER NOT EVALUATED OR CONTEMPLATED BY NATIONAL INSTRUMENTS,
THE USER OR APPLICATION DESIGNER IS ULTIMATELY RESPONSIBLE FOR VERIFYING AND
VALIDATING THE SUITABILITY OF NATIONAL INSTRUMENTS PRODUCTS WHENEVER NATIONAL
INSTRUMENTS PRODUCTS ARE INCORPORATED IN A SYSTEM OR APPLICATION, INCLUDING,
WITHOUT LIMITATION, THE APPROPRIATE DESIGN, PROCESS AND SAFETY LEVEL OF SUCH
SYSTEM OR APPLICATION.

© National Instruments Corporation v SCXI-1122 User Manual
Contents
About This Manual.............................................................................................................ix
Organization of This Manual .........................................................................................ix
Conventions Used in This Manual.................................................................................x
The National Instruments Documentation Set...............................................................xi
Related Documentation..................................................................................................xi
Customer Communication .............................................................................................xii
Chapter 1
Introduction ..........................................................................................................................1-1
What Your Kit Should Contain......................................................................................1-1
Software Programming Choices ....................................................................................1-2
LabVIEW and LabWindows Application Software ..........................................1-2
NI-DAQ Driver Software...................................................................................1-2
Register-Level Programming.............................................................................1-4
Optional Equipment .......................................................................................................1-4
Custom Cables ...................................................................................................1-5
Unpacking ......................................................................................................................1-5
Chapter 2
Configuration and Installation.......................................................................................2-1
Module Configuration....................................................................................................2-1
Digital Signal Connections ................................................................................2-3
Analog Configuration ........................................................................................2-3
Current-Loop Receivers.........................................................................2-4
Hardware Installation.....................................................................................................2-6
Chapter 3
Signal Connections .............................................................................................................3-1
Front Connector .............................................................................................................3-3
Front Signal Connection Descriptions ...............................................................3-4
Analog Input Channel Signal Connections............................................3-5
Excitation Channel Signal Connections.................................................3-8
Excitation Level .........................................................................3-8
Using the Internal Half-Bridge Completion...............................3-9
Temperature Sensor Connection........................................................................3-9
Rear Signal Connector ...................................................................................................3-10
Rear Signal Connection Descriptions ................................................................3-11
Analog Output Signal Connections........................................................3-11
Digital I/O Signal Connections..............................................................3-12
Chapter 4
Theory of Operation ..........................................................................................................4-1
Functional Overview......................................................................................................4-1
Rear Signal Connector, SCXIbus Connector, and SCXIbus Interface ..............4-3
Digital Control Circuitry....................................................................................4-3
Analog Circuitry ................................................................................................4-3
Analog Input Channels...........................................................................4-3
Excitation Output Channels ...................................................................4-5

Contents
SCXI-1122 User Manual vi © National Instruments Corporation
Chapter 5
Calibration.............................................................................................................................5-1
Overview........................................................................................................................5-1
Calibration Procedure ....................................................................................................5-1
Calibration Equipment Requirements................................................................5-1
Gain and Offset Calibration ...............................................................................5-2
Excitation Calibration ........................................................................................5-4
Appendix A
Specifications........................................................................................................................A-1
Analog Input ..................................................................................................................A-1
Excitation .......................................................................................................................A-3
Physical ..........................................................................................................................A-3
Environment...................................................................................................................A-3
Appendix B
Customer Communication...............................................................................................B-1
Glossary......................................................................................................................Glossary-1
Index ................................................................................................................................Index-1

Contents
© National Instruments Corporation vii SCXI-1122 User Manual
Figures
Figure1-1. The Relationship between the Programming Environment, NI-DAQ, and
Your Hardware................................................................................................... 1-3
Figure2-1. SCXI-1122 Parts Locator Diagram.................................................................... 2-2
Figure3-1. SCXI-1122 Front Connector Pin Assignments..................................................3-3
Figure3-2. Ground-Referenced Signal Connection with High Common-Mode Voltage.... 3-6
Figure3-3. Floating Signal Connection Referenced to Chassis Ground for Better SNR..... 3-6
Figure3-4. Floating AC-Coupled Signal Connection Referenced
to Chassis Ground for Better SNR.....................................................................3-6
Figure3-5. AC-Coupled Signal Connection with High Common-Mode Voltage............... 3-7
Figure3-6. Avoiding Relay Wear by Sampling and Averaging Rather Than
Single-Sample Channel Scanning...................................................................... 3-8
Figure3-7. Connecting a Quarter-Bridge Strain Gauge to Channel 0.................................. 3-9
Figure3-8. SCXI-1122 Rear Signal Connector Pin Assignments........................................ 3-10
Figure4-1. SCXI-1122 Block Diagram................................................................................ 4-2
Figure4-2. Series Connection with Current Excitation........................................................ 4-6
Figure4-3. Four-Wire Scan Connection with Multiplexed Current Excitation................... 4-6
Tables
Table2-1. Digital Signal Connection Jumper Settings....................................................... 2-3
Table2-2. Jumper W1 Settings........................................................................................... 2-4
Table2-3. User-Defined Current Receiver Resistors.......................................................... 2-4
Table3-1. Maximum Load per Excitation Channel............................................................ 3-9
Table3-2. SCXIbus to SCXI-1122 Rear Signal Connector to DAQ Board Pin
Equivalences...................................................................................................... 3-13
Table4-1. Sense/Current Output Channel Associations..................................................... 4-4
Table4-2. Pros and Cons of Two-Wire and Four-Wire Connections
with Current Excited Transducers...................................................................... 4-7
Table5-1. Maximum Allowable Error Ranges................................................................... 5-4

© National Instruments Corporation ix SCXI-1122 User Manual
About This Manual
This manual describes the electrical and mechanical aspects of the SCXI-1122 and contains
information concerning its operation. The SCXI-1122 is a member of the National Instruments
Signal Conditioning eXtensions for Instrumentation (SCXI) Series for the National Instruments
DAQ plug-in boards. This module is designed for signal conditioning of strain gauges, RTDs,
thermistors, thermocouples, volt and millivolt sources, and 4 to 20 mA sources or 0 to 20 mA
process-current sources where high common-mode voltages exist. The SCXI-1122 operates as 16
isolated input channels, one isolated current excitation channel, and one voltage excitation channel.
All 16 channels are isolated from earth ground but not from each other. The excitation circuits are
both isolated from earth ground, the input channels, and between each other.
Organization of This Manual
The SCXI-1122 User Manual is organized as follows:
Chapter 1, Introduction, describes the SCXI-1122; lists the contents of your SCXI-1122 kit;
describes the optional software, optional equipment, and custom cables; and explains how to
unpack the SCXI-1122.
Chapter 2, Configuration and Installation, describes how to configure the SCXI-1122
jumpers and how to install the SCXI-1122 into the SCXI chassis.
Chapter 3, Signal Connections, describes the input and output signal connections to the
SCXI-1122 module via the SCXI-1122 front connector and rear signal connector. This
chapter also includes specifications and connection instructions for the signals on the
SCXI-1122 connectors.
Chapter 4, Theory of Operation, contains a functional overview of the SCXI-1122 module
and explains the operation of each functional unit making up the SCXI-1122.
Chapter 5, Calibration, discusses the calibration procedures for the SCXI-1122.
Appendix A, Specifications, lists the specifications for the SCXI-1122.
Appendix B, Customer Communication, contains forms you can use to request help from
National Instruments or to comment on our products.
The Glossary contains an alphabetical list and description of terms used in this manual,
including abbreviations, acronyms, metric prefixes, mnemonics, symbols, and terms.
The Index contains an alphabetical list of key terms and topics in this manual, including the
page where you can find each one.

About This Manual
SCXI-1122 User Manual x © National Instruments Corporation
Conventions Used in This Manual
The following conventions are used in this manual.
bold italic Bold italic text denotes a note, caution, or warning.
italic Italic text denotes emphasis, a cross reference, or an introduction to a key
concept.
Lab board Lab board refers to the Lab-LC, Lab-NB, Lab-PC, and Lab-PC+ boards
unless otherwise noted.
MC MC refers to the Micro Channel series computers.
MIO board MIO board refers to the National Instruments multichannel I/O DAQ
boards, AT-MIO-16, MC-MIO-16, AT-MIO-16F-5,
AT-MIO-16X, AT-MIO-16D, AT-MIO-64F-5, NB-MIO-16, and
NB-MIO-16X, unless otherwise noted.
monospace Lowercase text in this font denotes text or characters that are to be literally
input from the keyboard, sections of code, programming examples, and
syntax examples. This font is also used for the proper names of disk
drives, paths, directories, programs, subprograms, subroutines, device
names, functions, variables, filenames, and extensions, and for statements
and comments taken from program code.
NB NB refers to the NuBus series computers.
PC PC refers to the IBM PC/XT, the IBM PC AT, and compatible computers.
SCXIbus SCXIbus refers to the backplane in the chassis. A signal on the backplane
is referred to as the SCXIbus <signal name> line (or signal). The
SCXIbus descriptor may be omitted when the meaning is clear.
Descriptions of all SCXIbus signals are in Chapter 3, Signal Connections.
Slot 0 Slot 0 refers to the power supply and control circuitry in the SCXI chassis.
Abbreviations, acronyms, metric prefixes, mnemonics, symbols, and terms are listed in the
Glossary.
!This symbol refers to a caution that must be taken when operating this
equipment. This symbol is found on the equipment and near the explanation of
the caution in the manual.

About This Manual
© National Instruments Corporation xi SCXI-1122 User Manual
The National Instruments Documentation Set
The SCXI-1122 User Manual is one piece of the documentation set for your SCXI system. You
should have six types of manuals. Use these different types of manuals as follows:
•Getting Started with SCXI–This is the first manual you should read. It gives an overview of
the SCXI system and contains the most commonly needed information for the modules,
chassis, and software.
• Your SCXI module user manuals–These manuals contain detailed information about signals
connections and module configuration. They also explain in greater detail how the module
works and application hints.
• Your DAQ board user manuals–These manuals have detailed information about the DAQ
board that plugs into your computer. Use these manuals for board installation and
configuration instructions, specification information about your DAQ board, and application
hints.
• Software manuals–Examples of software manuals you might have are the LabVIEW and
LabWindows®manual sets and the NI-DAQ manuals. After you have set up your hardware
system, use either the application software (LabVIEW or LabWindows) manuals or the
NI-DAQ manuals to help you write your application. If you have a large and complicated
system, it is worthwhile to look through the software manuals before you configure your
hardware.
• Accessory manuals–These are the terminal block and cable assembly installation guides.
They explain how to physically connect the relevant pieces of the system together. Consult
these when you are making your connections.
• SCXI chassis manuals–These manuals contain maintenance information on the chassis,
installation instructions, and information for making custom modules.
Related Documentation
The following National Instruments manual contains detailed information for the register-level
programmer:
•SCXI-1122 Register-Level Programmer Manual (part number 340696-01)
This manual is available from National Instruments by request. If you are using NI-DAQ,
LabVIEW, or LabWindows,you should not need the register-level programmer manual. Using
NI-DAQ, LabVIEW, or LabWindows is quicker and easier than and as flexible as using the low-
level programming described in the register-level programmer manual. Refer to Software
Programming Choices in Chapter 1, Introduction, of this manual to learn about your
programming options.

About This Manual
SCXI-1122 User Manual xii © National Instruments Corporation
Customer Communication
National Instruments wants to receive your comments on our products and manuals. We are
interested in the applications you develop with our products, and we want to help if you have
problems with them. To make it easy for you to contact us, this manual contains comment and
configuration forms for you to complete. These forms are in Appendix B, Customer
Communication, at the end of this manual.

© National Instruments Corporation 1-1 SCXI-1122 User Manual
Chapter 1
Introduction
This chapter describes the SCXI-1122; lists the contents of your SCXI-1122 kit; describes the
optional software, optional equipment, and custom cables; and explains how to unpack the
SCXI-1122.
The SCXI-1122 has 16 isolated input channels and two isolated excitation channels. The
SCXI-1122 is a module for signal conditioning of strain gauges, RTDs, thermistors,
thermocouples, volt and millivolt sources, 4 to 20 mA current sources, and 0 to 20 mA process-
current sources. The SCXI-1122 can operate in two modes–two-wire scan mode with all 16
input channels used for input, or the four-wire scan mode with the eight upper channels
configured as sense leads for connecting inputs and the lower eight channels configured as
current output channels. The SCXI-1122 inputs are multiplexed to a single output, which drives
a single DAQ board channel.
The SCXI-1122 operates with full functionality with the National Instruments MIO-16,
Lab-PC+, and the SCXI-1200 boards. You can use the Lab and PC-LPM-16 boards with the
SCXI-1122, but these boards cannot scan the module. These boards can perform only single-
channel reads. You can multiplex several SCXI-1122s into a single channel, thus greatly
increasing the number of isolated analog input signals that you can digitize.
You can add the SCXI-1322 shielded terminal block, which has screw terminals to which you
can easily attach the input signals to the SCXI-1122. In addition, the SCXI-1322 has a
temperature sensor for cold-junction compensation of thermocouples. This cold-junction
reference (CJR) is multiplexed with the 16 input channels.
What Your Kit Should Contain
The contents of the SCXI-1122 kit (part number 776572-22) are listed as follows:
Kit Component Part Number
SCXI-1122 module 182366-01
SCXI-1122 User Manual 320516-01
If your kit is missing any of the components, contact National Instruments.
Detailed specifications of the SCXI-1122 are listed in Appendix A, Specifications.

Introduction Chapter 1
SCXI-1122 User Manual 1-2 © National Instruments Corporation
Software Programming Choices
There are four options to choose from when programming your National Instruments plug-in
DAQ board and SCXI hardware. You can use LabVIEW, LabWindows, NI-DAQ, or register-
level programming software.
LabVIEW and LabWindows Application Software
LabVIEW and LabWindows are innovative program development software packages for data
acquisition and control applications. LabVIEW uses graphical programming, whereas
LabWindows enhances traditional programming languages. Both packages include extensive
libraries for data acquisition, instrument control, data analysis, and graphical data presentation.
LabVIEW currently runs on three different platforms–AT/MC/EISA computers running
Microsoft Windows, the Macintosh platform, and the Sun SPARCstation platform. LabVIEW
features interactive graphics, a state-of-the-art user interface, and a powerful graphical
programming language. The LabVIEW Data Acquisition VI Library, a series of VIs for using
LabVIEW with National Instruments boards, is included with LabVIEW. The LabVIEW Data
Acquisition VI Libraries are functionally equivalent to the NI-DAQ software.
LabWindows has two versions–LabWindows for DOS is for use on PCs running DOS, and
LabWindows/CVI is for use on PCs running Windows and Sun SPARCstations.
LabWindows/CVI features interactive graphics, a state-of-the-art user interface, and uses the
ANSI standard C programming language. The LabWindows Data Acquisition Library, a series
of functions for using LabWindows with National Instruments boards, is included with
LabWindows for DOS and LabWindows/CVI. The LabWindows Data Acquisition libraries are
functionally equivalent to the NI-DAQ software.
Using LabVIEW or LabWindows software will greatly diminish the development time for your
data acquisition and control application. Part numbers for these software products are as follows:
Software Part Number
LabVIEW for Windows 776670-01
LabVIEW for Macintosh 776141-01
LabWindows for DOS 776475-01
LabWindows/CVI for Windows 776800-01
NI-DAQ Driver Software
The NI-DAQ driver software is included at no charge with all National Instruments DAQ boards.
NI-DAQ has an extensive library of functions that you can call from your application
programming environment. These functions include routines for analog input (A/D conversion),
buffered data acquisition (high-speed A/D conversion), analog output (D/A conversion),
waveform generation, digital I/O, counter/timer operations, SCXI, RTSI, self-calibration,
messaging, and acquiring data to extended memory.

Chapter 1 Introduction
© National Instruments Corporation 1-3 SCXI-1122 User Manual
NI-DAQ also internally addresses many of the complex issues between the computer and the
plug-in board such as programming interrupts and DMA controllers. NI-DAQ maintains a
consistent software interface among its different versions so that you can change platforms with
minimal modifications to your code. Figure 1-1 illustrates the relationship between NI-DAQ and
LabVIEW and LabWindows. You can see that the data acquisition parts of LabVIEW and
LabWindows are functionally equivalent to the NI-DAQ software.
LabWindows
(PC)
LabVIEW 
(PC or Macintosh)
Conventional 
Programming 
Environment 
(PC or Macintosh)

NI-DAQ
Driver Software
Data Acquisition
Boards or
SCXI Hardware
Personal 
Computer
or
Workstation
Figure 1-1. The Relationship between the Programming Environment,
NI-DAQ, and Your Hardware
The National Instruments PC, AT, and MC Series DAQ boards are packaged with NI-DAQ
software for PC compatibles. NI-DAQ software for PC compatibles comes with language
interfaces for Professional BASIC, Turbo Pascal, Turbo C, Turbo C++, Borland C++, and
Microsoft C for DOS; and Visual Basic, Turbo Pascal, Microsoft C with SDK, and Borland C++
for Windows. You can use your SCXI-1122, together with other PC, AT, and MC Series DAQ
boards and SCXI hardware, with NI-DAQ software for PC compatibles.
The National Instruments NB Series DAQ boards are packaged with NI-DAQ software for
Macintosh. NI-DAQ software for Macintosh comes with language interfaces for MPW C,
THINK C, Pascal, and Microsoft QuickBASIC. Any language that uses Device Manager
Toolbox calls can access NI-DAQ software for Macintosh. You can use NB Series DAQ boards
and SCXI hardware with NI-DAQ software for Macintosh.

Introduction Chapter 1
SCXI-1122 User Manual 1-4 © National Instruments Corporation
Register-Level Programming
The final option for programming any National Instruments DAQ hardware is to write register-
level software. Writing register-level programming software can be very time consuming and
inefficient, and is not recommended for most users. The only users who should consider writing
register-level software should meet at least one of the following criteria:
• National Instruments does not support your operating system or programming language.
• You are an experienced register-level programmer who is more comfortable writing your
own register-level software.
Always consider using NI-DAQ, LabVIEW, or LabWindows to program your National
Instruments DAQ hardware. Using the NI-DAQ, LabVIEW, or LabWindows software is easier
than and as flexible as register-level programming, and can save you weeks of development time.
The SCXI-1122 User Manual and your software manuals contain complete instructions for
programming your DAQ board with NI-DAQ, LabVIEW, or LabWindows. If you are using
NI-DAQ, LabVIEW, or LabWindows to control your board, you should not need the register-
level programmer manual. The SCXI-1122 Register-Level Programmer Manual contains low-
level programming details, such as register maps, bit descriptions, and register programming
hints, that you will need only for register-level programming. Some hardware user manuals
include register map descriptions and register programming hints. If your manual does not
contain a register map description and you want to obtain the register-level programmer manual,
please fill out the Register-Level Programmer Manual Request Form at the end of this manual
and send it to National Instruments.
Optional Equipment
Equipment Part Number
SCXI-1322 front terminal block 776573-22
SCXI-1340 cable assembly 776574-40
SCXI-1341 Lab-NB/Lab-PC/Lab-PC+ cable assembly 776574-41
SCXI-1342 PC-LPM-16 cable assembly 776574-42
SCXI-1343 rear screw terminal adapter 776574-43
SCXI-1344 Lab-LC cable assembly 776574-44
SCXI-1345 shielded cable with adapter, 1 m
2 m
5 m
10 m
776574-451
776574-452
776574-455
776574-450
SCXI-1350 multichassis adapter 776575-50
SCXI process-current resistor kit1776582-01
Standard ribbon cable, 0.5 m
1.0 m 180524-05 180524-10
1 Resistor kit needed to perform current measurements. (See pages 2-4)
Refer to Chapter 3, Signal Connections, and to your cable installation guide for additional
information on cabling, connectors, and adapters.

Chapter 1 Introduction
© National Instruments Corporation 1-5 SCXI-1122 User Manual
Custom Cables
The SCXI-1122 rear signal connector is a 50-pin male ribbon-cable header. The manufacturer
part number that National Instruments uses for this header is as follows:
• AMP Inc. (part number 1-103310-0)
The mating connector for the SCXI-1122 rear signal connector is a 50-position polarized
ribbon-socket connector with strain relief. National Instruments uses a polarized or keyed
connector to prevent inadvertent upside-down connection to the SCXI-1122. Recommended
manufacturer part numbers for this mating connector are as follows:
• Electronic Products Division/3M (part number 3425-7650)
• T&B/Ansley Corporation (part number 609-5041CE)
Standard 50-conductor, 28 AWG, stranded ribbon cables that you can use with these connectors
are as follows:
• Electronic Products Division/3M (part number 3365/50)
• T&B/Ansley Corporation (part number 171-50)
The SCXI-1122 front connector is a 48-pin DIN C male connector. The manufacturer part
number that National Instruments uses for this connector is as follows:
• ERNI (part number 913523)
The mating connector for the SCXI-1122 front connector is a 48-pin DIN C female connector.
National Instruments uses a polarized connector to prevent inadvertent upside-down connection
to the SCXI-1122. The manufacturer part number that National Instruments uses for this
connector is as follows:
• ERNI (part number 913524; right-angle pins)
Unpacking
Your SCXI-1122 module is shipped in an antistatic package to prevent electrostatic damage to
the module. Electrostatic discharge can damage several components on the module. To avoid
such damage in handling the module, take the following precautions.
• Ground yourself via a grounding strap or by holding a grounded chassis such as your SCXI
chassis.
• Touch the antistatic package to a metal part of your SCXI chassis before removing the
module from the package.
• Remove the module from the package and inspect the module for loose components or any
other sign of damage. Notify National Instruments if the module appears damaged in any
way. Do not install a damaged module into your SCXI chassis.
•Never touch the exposed pins of connectors.

© National Instruments Corporation 2-1 SCXI-1122 User Manual
Chapter 2
Configuration and Installation
This chapter describes how to configure the SCXI-1122 jumpers and how to install the
SCXI-1122 into the SCXI chassis.
Module Configuration
The SCXI-1122 contains two jumpers that are shown in the parts locator diagram in Figure 2-1.
Jumper W2 connects a pullup resistor to the SERDATOUT signal on the rear signal connector.
Jumper W1 configures the guard and the analog output ground, and enables the
pseudodifferential reference mode.
You must use software to further configure the module. Refer to your software manuals, or to
the SCXI-1122 Register-Level Programmer Manual if you are a register-level programmer.

Configuration and Installation Chapter 2
SCXI-1122 User Manual 2-2 © National Instruments Corporation
Figure 2-1. SCXI-1122 Parts Locator Diagram

Chapter 2 Configuration and Installation
© National Instruments Corporation 2-3 SCXI-1122 User Manual
Digital Signal Connections
Note: If nothing is cabled to the SCXI-1122 rear signal connector, the position of
jumper W2 is irrelevant.
The SCXI-1122 has one jumper–jumper W2–for communication between the DAQ board and
the SCXIbus, shown in Table 2-1.
Table 2-1. Digital Signal Connection Jumper Settings
Jumper Description Configuration
DAQ board to
SCXIbus
communication
Position 1 (pullup)–Use this setting
for a single-chassis system.
Connects a 2.2 kΩpullup resistor to
the SERDATOUT line. (factory
setting)
W2
1
W2
Position 3 (unmarked position, no
pullup)–Use this setting for
additional chassis in a multichassis
system. No pullup resistor is
connected to the SERDATOUT line.
W2
1
If a module is not connected to a DAQ board, the position of W2 is irrelevant. The MISO line
on the SCXI-1122 module is for reading the Module ID Register, the Status Register, and the
EEPROM. National Instruments software does not read the Module ID automatically–you must
indicate to the software which module is in which slot.
An open-collector driver (a driver that actively drives low or goes to high-impedance state,
relying on a pullup resistor to make the signal line go high) drives the SERDATOUT line. When
using a single chassis, set jumper W2 in position 1 on the SCXI-1122 that is connected to the
DAQ board. In this setting, the module drives MISO to SERDATOUT and connects the
necessary pullup resistor to the SERDATOUT line. When using multiple chassis, set jumper W2
to position 1 on only one of the SCXI-1122s that are cabled to the DAQ board. It does not
matter which of the SCXI-1122s that are cabled to the DAQ board has the pullup connected. Set
jumper W2 in position 3 on all of the other SCXI-1122 modules that are cabled to the DAQ
board because if too many pullup resistors are attached to the SERDATOUT line, the drivers
cannot drive the line low.
Analog Configuration
The SCXI-1122 has one analog configuration jumper–jumper W1–for grounding, shielding, and
reference mode selection, shown in Table 2-2.

Configuration and Installation Chapter 2
SCXI-1122 User Manual 2-4 © National Instruments Corporation
Table 2-2. Jumper W1 Settings
Jumper Description Configuration
Grounding,
shielding, and
reference mode
selection
Unconnected position (factory setting)
W1
B
AR0 R1 R2
Connects the analog reference to the
analog output ground AOGND (pins 1
and 2 on the rear signal connector).
Select this configuration if you are
using an RSE DAQ board. Do not use
a differential input DAQ board when
jumper W1 is in this position.
B
AR0 R1 R2
W1
Connects SCXIbus guard to the analog
reference
B
AR0 R1 R2
W1
W1
Enables the pseudodifferential
reference mode and connects the
analog reference to the OUTREF pin
on the rear signal connector. Select
this mode when the SCXI-1122 has to
operate with DAQ boards that have a
nonreferenced single-ended (NRSE)
input. Do not use differential input
DAQ boards when jumper W1 is in
this position.
B
AR0 R1 R2
W1
Current-Loop Receivers
The SCXI-1122 has pads for transforming individual channels to current-to-voltage converters.
National Instruments offers an SCXI process current pack, which consists of a package of four
249 Ω, 0.1%, 5 ppm, 1/4 W resistors. You can find the part number for this kit in the Optional
Equipment section of Chapter 1, Introduction. Table 2-3 shows the input channel and its
corresponding resistor reference designator.
Table 2-3. User-Defined Current Receiver Resistors
Input Channel Resistor Reference Designator
0R1
1R2
2R3
3R4
(continues)