National Instruments NI PXI-7831R User Manual

Reconfigurable I/O

NI PXI-7831R User Manual

Reconfigurable I/O Devices for PXI/CompactPCI Bus Computers

NI PXI-7831R User Manual

April 2003 Edition

Part Number 370489A-01

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The NI PXI-7831R is warranted against defects in materials and workmanship for a period of one year from the date of shipment, as evidenced
by receipts or other documentation. National Instruments will, at its option, repair or replace equipment that proves to be defective during the
warranty period. This warranty includes parts and labor.

The media on which you receive National Instruments software are warranted not to fail to execute programming instructions, due to defects
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Determining FCC Class

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Consult the FCC Web site at

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www.fcc.gov for more information.

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To obtain the DoC for this product, click Declaration of Conformity at
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ni.com/hardref.nsf/. This Web site lists the DoCs

Contents

About This Manual

Conventions ...................................................................................................................vii

Reconfigurable I/O Documentation...............................................................................viii

Related Documentation..................................................................................................viii

Chapter 1
Introduction

About the Reconfigurable I/O Devices..........................................................................1-1

Using PXI with CompactPCI.........................................................................................1-2

What You Need to Get Started ......................................................................................1-3

Getting Started with Windows 2000/XP .........................................................1-3

Getting Started with the RT Module ...............................................................1-4

Overview of Reconfigurable I/O ...................................................................................1-5

Reconfigurable I/O Concept............................................................................1-5

Reconfigurable I/O Architecture .....................................................................1-6

Reconfigurable I/O Applications.....................................................................1-8

Software Development ..................................................................................................1-8

FPGA Module .................................................................................................1-9

RT Module.......................................................................................................1-9

Cables and Optional Equipment ....................................................................................1-9

Custom Cabling .............................................................................................................1-10

Unpacking......................................................................................................................1-11

Safety Information .........................................................................................................1-11

Flexible Functionality .......................................................................1-5

User-Defined I/O Resources .............................................................1-6

Device-Embedded Logic and Processing .........................................1-6

Chapter 2
Hardware Overview of the NI PXI-7831R

Analog Input ..................................................................................................................2-2

Input Modes.....................................................................................................2-3

Input Range .....................................................................................................2-3

Connecting Analog Input Signals ..................................................................................2-4

Types of Signal Sources ................................................................................................2-5

Floating Signal Sources...................................................................................2-6

Ground-Referenced Signal Sources ................................................................2-6

Input Modes ...................................................................................................................2-6

Differential Connection Considerations (DIFF Input Mode)..........................2-8

© National Instruments Corporation v NI PXI-7831R User Manual

Contents

Analog Output ............................................................................................................... 2-14

Connecting Analog Output Signals ............................................................................... 2-14

Digital I/O...................................................................................................................... 2-15

Connecting Digital I/O Signals ..................................................................................... 2-15

PXI Trigger Bus ............................................................................................................ 2-18

PXI Local Bus ............................................................................................................... 2-19

Switch Settings .............................................................................................................. 2-20

Power Connections........................................................................................................ 2-21

Field Wiring Considerations.......................................................................................... 2-21

Chapter 3
Calibration

Loading Calibration Constants ...................................................................................... 3-1

Internal Calibration........................................................................................................ 3-1

External Calibration....................................................................................................... 3-2

Differential Connections for Ground-Referenced Signal Sources ... 2-8
Differential Connections for Nonreferenced or

Floating Signal Sources ................................................................. 2-9

Single-Ended Connection Considerations ...................................................... 2-11

Single-Ended Connections for Floating

Signal Sources (RSE Input Mode)................................................. 2-12

Single-Ended Connections for Grounded

Signal Sources (NRSE Input Mode)..............................................2-12

Common-Mode Signal Rejection Considerations........................................... 2-13

Appendix A
Specifications

Appendix B
Connecting I/O Signals

Appendix C
Using the SCB-68 Shielded Connector Block

Appendix D
Technical Support and Professional Services

Glossary

NI PXI-7831R User Manual vi ni.com

About This Manual

This manual describes the electrical and mechanical aspects of the
National Instruments PXI-7831R device and contains information
concerning its operation and programming.

The NI PXI-7831R device is a Reconfigurable I/O (RIO) device.
The NI PXI-7831R contains eight independent, 16-bit analog input (AI)
channels, eight independent, 16-bit analog output (AO) channels, and
96 digital I/O (DIO) lines.

Conventions

The following conventions appear in this manual:

<> Angle brackets that contain numbers separated by an ellipsis represent a

range of values associated with a bit or signal name—for example,
DIO<3..0>.

» The » symbol leads you through nested menu items and dialog box options

to a final action. The sequence File»Page Setup»Options directs you to
pull down the File menu, select the Page Setup item, and select Options
from the last dialog box.

This icon denotes a note, which alerts you to important information.

This icon denotes a caution, which advises you of precautions to take to
avoid injury, data loss, or a system crash. When this symbol is marked on
the device, refer to the Safety Information section of Chapter 1,

Introduction, for precautions to take.

bold Bold text denotes items that you must select or click in the software, such

as menu items and dialog box options. Bold text also denotes parameter
names and hardware labels.

italic Italic text denotes variables, emphasis, a cross reference, or an introduction

to a key concept. This font also denotes text that is a placeholder for a word
or value that you must supply.

monospace Text in this font denotes text or characters that you should enter 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,

© National Instruments Corporation vii NI PXI-7831R User Manual

About This Manual

programs, subprograms, subroutines, device names, functions, operations,
variables, filenames and extensions, and code excerpts.

Reconfigurable I/O Documentation

The NI PXI-7831R User Manual is one piece of the documentation set for
your RIO system and application. Depending on the hardware and software
you use for your application, you could have any of several types of
documentation. Use the documentation you have as follows:

• Where to Start with the NI PXI-7831R—This document lists what you
need to get started, describes how to unpack and install the hardware,
and contains information about connecting signals to the
NI PXI-7831R.

• NI PXI-7831R User Manual—This manual contains detailed
information about the NI PXI-7831R hardware.

• LabVIEW FPGA Module Release Notes—This document contains
information about installing and getting started with the FPGA
Module.

• LabVIEW FPGA Module User Manual—This manual describes how
to use the FPGA Module.

• LabVIEW Help—This help contains information about using various
virtual instruments (VIs) with the NI PXI-7831R and using the FPGA
Module and the LabVIEW Real-Time (RT) Module.

• LabVIEW Real-Time Module User Manual—This manual contains
information about how to install and use the RT Module.

Related Documentation

The following documents contain information you might find helpful:

• NI Developer Zone tutorial, Field Wiring and Noise Considerations
for Analog Signals, at

• PICMG CompactPCI 2.0 R3.0

• PXI Hardware Specification Revision 2.1

• PXI Software Specification Revision 2.1

NI PXI-7831R User Manual viii ni.com

ni.com/zone

Introduction

This chapter describes the NI PXI-7831R, describes the concept of the
Reconfigurable I/O (RIO) device, lists what you need to get started,
describes the optional software and optional equipment, explains how
to unpack the hardware, and contains safety information about the
NI PXI-7831R.

About the Reconfigurable I/O Devices

Thank you for purchasing the NI PXI-7831R. This RIO device has 96
digital I/O (DIO) lines, 8 independent, 16-bit analog output (AO) channels,
and 8 independent, 16-bit analog input (AI) channels.

A user-reconfigurable field-programmable gate array (FPGA) controls the
digital and analog I/O on the NI PXI-7831R. The FPGA on the RIO device
allows you to define the functionality and timing of the device, whereas
traditional multifunction I/O (MIO) devices have a fixed functionality
provided by an application-specific integrated circuit (ASIC). You can
change the functionality of the FPGA on the RIO device by using
LabVIEW, a graphical programming environment, and the LabVIEW
FPGA Module to create and download a custom virtual instrument (VI) to
the FPGA. You can reconfigure the RIO device with a new VI at any time.
Using LabVIEW, you can graphically design the timing and functionality
of the RIO device without having to learn the low-level programming
language or hardware description language (HDL) that is traditionally used
for FPGA design. If you only have LabVIEW and do not have the FPGA
Module, you cannot create new FPGA VIs but you can create VIs that run
in LabVIEW to control existing FPGA VIs.

1

Some applications require tasks such as real-time, floating-point
processing or data logging while performing I/O and logic on the RIO
device. You can use the LabVIEW Real-Time (RT) Module to perform
these additional applications while also communicating with and
controlling the RIO device.

The RIO device contains flash memory to store VIs for instant loading of
the FPGA when the system is powered on.

© National Instruments Corporation 1-1 NI PXI-7831R User Manual

Chapter 1 Introduction

The PXI chassis has the Real-Time System Integration (RTSI) bus to easily
synchronize several measurement functions to a common trigger or timing
event. The RTSI bus is implemented on the PXI trigger bus on the PXI
backplane. The RTSI bus can route timing and trigger signals between as
many as seven PXI devices in your system.

Refer to Appendix A, Specifications, for detailed specifications of the RIO
device.

Using PXI with CompactPCI

Using PXI compatible products with standard CompactPCI products is an
important feature provided by PXI Hardware Specification Revision 2.1
and PXI Software Specification Revision 2.1. If you use a PXI-compatible
plug-in card in a standard CompactPCI chassis, you cannot use
PXI-specific functions, but you can still use the basic plug-in card
functions. For example, the RTSI bus on the RIO device is available in a
PXI chassis, but not in a CompactPCI chassis.

The CompactPCI specification permits vendors to develop sub-buses that
coexist with the basic PCI interface on the CompactPCI bus. Compatible
operation is not guaranteed between CompactPCI devices with different
sub-buses nor between CompactPCI devices with sub-buses and PXI.
The standard implementation for CompactPCI does not include these
sub-buses. The RIO device works in any standard CompactPCI chassis
adhering to PICMG CompactPCI 2.0 R3.0.

PXI-specific features are implemented on the J2 connector of the
CompactPCI bus. Table 1-1 lists the J2 pins used by the NI PXI-7831R.
The NI PXI-7831R is compatible with any CompactPCI chassis with a
sub-bus that does not drive these lines. Even if the sub-bus is capable of
driving these lines, the RIO device is still compatible as long as those pins
on the sub-bus are disabled by default and are never enabled.

Caution Damage can result if the J2 lines are driven by the sub-bus.

NI PXI-7831R User Manual 1-2 ni.com

Chapter 1 Introduction

Table 1-1. Pins Used by the NI PXI-7831R

NI PXI-7831R Signal PXI Pin Name PXI J2 Pin Number

PXI Trigger<0..7> PXI Trigger<0..7> A16, A17, A18, B15, B18, C18,

E16, E18

PXI Clock 10 MHz PXI Clock 10 MHz E17

PXI Star Trigger PXI Star Trigger D17

LBLSTAR<0..12> LBL<0..12> A1, A19, C1, C19, C20, D1, D2,

D15, D19, E1, E2, E19, E20

LBR<0..12> LBR<0..12> A2, A3, A20, A21, B2, B20, C3,

C21, D3, D21, E3, E15, E21

What You Need to Get Started

This section contains two lists that detail what you need to get started using
the NI PXI-7831R with Windows 2000/XP or the RT Module.

Getting Started with Windows 2000/XP

To set up and use the NI PXI-7831R with Windows 2000/XP, you need the
following items:

❑ NI PXI-7831R

❑ The following software packages:

– LabVIEW version 7.0 or later

– NI Device Drivers CD

– FPGA Module version 7.0 or later (required to develop custom

FPGA VIs for the RIO device)

❑ PXI/CompactPCI chassis and a PXI/CompactPCI embedded

controller, running Windows 2000/XP (or any computer running
Windows 2000/XP and an MXI-3 link to a PXI/CompactPCI chassis)

❑ At least one cable and terminal block for connecting signals to the

NI PXI-7831R

© National Instruments Corporation 1-3 NI PXI-7831R User Manual

Chapter 1 Introduction

❑ The following documents are included on the NI Device Drivers CD

and are also available at

– LabVIEW FPGA Module Release Notes

– LabVIEW FPGA Module User Manual

– Where to Start with the NI PXI-7831R

❑ The LabVIEW Help, which is available by selecting Help»VI,

Function, & How-To Help from LabVIEW.

Getting Started with the RT Module

To set up and use the NI PXI-7831R with the FPGA Module and the
RT Module, you need the following items:

❑ NI PXI-7831R

❑ The following software packages:

– LabVIEW version 7.0 or later

– NI Device Drivers CD

– FPGA Module version 7.0 or later (required to develop custom

FPGA VIs for the RIO device)

– RT Module version 7.0 or later

ni.com/manuals (optional):

❑ PXI/CompactPCI chassis and real-time PXI controller

❑ One of the following host computers, depending upon your

application, running Windows 2000/XP:

–PC

– Laptop computer

– PXI/CompactPCI embedded controller

❑ At least one cable and terminal block for connecting signals to the

NI PXI-7831R

❑ Category 5 (Cat-5) crossover cable (if the real-time PXI system is not

configured on a network). You need a regular network cable if you are
configured on a network.

NI PXI-7831R User Manual 1-4 ni.com

❑ The following documents are included on the NI Device Drivers CD

and are also available at

– LabVIEW FPGA Module Release Notes

– LabVIEW FPGA Module User Manual

– LabVIEW Real-Time Module User Manual

– Where to Start with the NI PXI-7831R

❑ The LabVIEW Help, which is available by selecting Help»VI,

Function, & How-To Help from LabVIEW.

Overview of Reconfigurable I/O

This section introduces the concept of RIO and describes how to use
the reconfigurable FPGA to build high-level functions in hardware.

Refer to Chapter 2, Hardware Overview of the NI PXI-7831R, for
descriptions of the physical I/O resources available on the NI PXI-7831R.

Reconfigurable I/O Concept

The NI PXI-7831R device is based on a reconfigurable FPGA core
surrounded by fixed I/O resources. The behavior of the reconfigurable core
can be configured to better match the requirements of the measurement and
control system. The behavior can be fully user defined and implemented as
a VI, creating an application-specific I/O device. In contrast, a traditional
data acquisition (DAQ) device uses a fixed core with predetermined
functionality.

Chapter 1 Introduction

ni.com/manuals (optional):

Flexible Functionality

Flexible functionality allows the RIO device to match individual
application requirements and to mimic the functionality of fixed I/O
devices, including I/O combinations not available in standard products. For
example, you can configure a RIO device in one application for three 32-bit
quadrature decoders and then reconfigure the RIO device in another
application for eight 16-bit event counters.

In timing and triggering applications, the flexible functionality of the RIO
device makes it an ideal complement to applications based on the RT
module, such as control and hardware-in-the-loop (HIL) simulations. For
example, you can configure the RIO device for a single timed loop in one
application and then reconfigure the device in another application for four
independent timed loops with separate I/O resources.

© National Instruments Corporation 1-5 NI PXI-7831R User Manual

Chapter 1 Introduction

User-Defined I/O Resources

With the RIO device, you can define both the combination of I/O resources
and the I/O resources themselves. You can also create new building blocks
on top of fixed I/O resources. For example, one application might require
an event counter that increments when a rising edge appears on any of three
digital input lines. Another application might require a digital line to be
asserted once an analog input exceeds a programmable threshold. You can
implement these user-defined behaviors in the hardware for fast,
deterministic performance.

Device-Embedded Logic and Processing

You can embed logic and processing in the FPGA of the RIO device.
Typical logic functions include Boolean operations, comparisons, and
basic mathematical operations. You can implement multiple functions
efficiently in the same design, operating sequentially or in parallel. It is
possible to implement more complex algorithms such as control loops,
but the size of the FPGA limits the scope of these algorithms.

Reconfigurable I/O Architecture

Figure 1-1, which illustrates a generic representation of RIO device, shows
an FPGA connected to fixed I/O resources and a bus interface.

Fixed I/O Resource

Fixed I/O Resource

FPGA

Bus Interface

Figure 1-1. High-Level FPGA Functional Overview

Fixed I/O Resource

Fixed I/O Resource

The fixed I/O resources include A/D converters (ADCs), D/A converters
(DACs), digital input or output lines, or other I/O resources. Software
accesses the RIO device through the bus interface, and the FPGA provides

NI PXI-7831R User Manual 1-6 ni.com

Chapter 1 Introduction

the connectivity between the bus interface and the fixed I/O, including any
timing, triggering, processing, and custom I/O required by the application.

Timing, triggering, processing, and custom I/O is provided by consuming
logic in the FPGA. Each fixed I/O resource used by the application
consumes a small portion of the FPGA logic, which is used to perform
basic control of the fixed I/O resource. The bus interface also consumes a
small portion of the FPGA logic to provide software access to the device.

The remaining FPGA logic is available for higher-level functions such as
timing, triggering, and counting. Each of these functions consumes varying
amounts of logic. For example, a typical 32-bit counter consumes 20 times
more logic than a DIO resource, while an 8-bit counter consumes five times
more logic than a DIO resource. Figures 1-2 and 1-3 illustrate the logic
used by the FPGA in two different applications. The application shown in
Figure 1-2 requires many fixed I/O resources, leaving little logic left over
for higher-level functions. The application in Figure 1-3 uses relatively few
I/O resources and has enough logic left over for several large functions.

AI0 AI1 AI2 AI3

DIO<0..7>

Bus Interface

DIO<8..15>

AO3 AO2 AO1 AO0

Figure 1-2. FPGA Logic Use in an Application with Many Fixed I/O Resources

© National Instruments Corporation 1-7 NI PXI-7831R User Manual

Chapter 1 Introduction

Counter

DIO<0..7>

Bus Interface

Figure 1-3. FPGA Logic Use in an Application with Higher-Level Functions

The FPGA is volatile and does not retain the VI when it is powered off.
Therefore, the VI must be reloaded every time power is turned on. The VI
comes from onboard flash memory or from the software over the bus
interface. One advantage to using flash memory is that the VI can start
executing almost immediately after power up, instead of waiting for the
computer to completely boot and load the FPGA. Refer to the LabVIEW
FPGA User Manual for more information about how to store your VI in
flash memory.

Reconfigurable I/O Applications

To create or obtain new VIs for your application, you can use the FPGA
Module, which allows the application to be specified using a subset of
LabVIEW. Arbitrary functionality can be defined for the RIO device. If
you are using the FPGA Module, refer to the FPGA Module examples
located in

LabVIEW 7.0\examples\FPGA.

Software Development

You can use LabVIEW with the FPGA Module to program the
NI PXI-7831R. To develop real-time applications that control the
NI PXI-7831R, you can use the RT Module with LabVIEW and the
FPGA Module.

PID

AO0

NI PXI-7831R User Manual 1-8 ni.com

FPGA Module

Note A software utility installed with the NI-RIO Device Drivers CD allows users without

the FPGA module to configure the NI PXI-7831R analog input mode, synchronize to the
PXI clock, and configure the device to automatically load FPGA VIs when powered on.

RT Module

Chapter 1 Introduction

The FPGA Module enables you to use LabVIEW to create VIs that run on
the RIO device, which contains a reconfigurable FPGA. The FPGA
Module includes a new function palette, which contains functions that run
on the FPGA on the RIO device. These functions can control the I/O,
timing, and logic of the RIO device and can generate interrupts for
synchronization. The FPGA Module synthesizes a VI into a form that can
be downloaded to the FPGA on the RIO device. The Interactive Front Panel
Communication with the FPGA Module allows you to interact with the VI
running on the FPGA. The FPGA Module also includes a palette of
functions for use in LabVIEW for Windows, or when targeting an RT
Module device, that create applications that wait for interrupts and that
control the FPGA by programmatically reading and writing to the device.

The RT Module extends the LabVIEW development environment to
deliver deterministic, real-time performance.

You can develop your RT Module application on a host computer
with graphical programming and then download the program to run on
an independent hardware target with a real-time operating system. The
RT Module allows you to use the NI PXI-7831R in PXI systems being
controlled in real time by a LabVIEW VI.

The NI PXI-7831R plug-in device is designed as a single-point AI, AO, and
DIO complement to the RT Module. Refer to
more information about the RT Module.

ni.com/labviewrt for

Cables and Optional Equipment

NI offers a variety of products to use with your device, including cables,
connector blocks, and other accessories as follows.

© National Instruments Corporation 1-9 NI PXI-7831R User Manual

Chapter 1 Introduction

Table 1-2. Cables and Accessories

Cable Cable Description Accessories

SH68-C68-S Shielded 68-pin VHDCI male

connector to female 0.050 series
D-type connector. The cable is
constructed with 34 twisted wire
pairs plus an overall shield.

NSC68-262650 Non-shielded cable connects from

68-pin VHDCI male connector to
two 26-pin female headers plus one
50-pin female header. The pinout of
these headers allows for direct
connection to 5B backplanes for
analog signal conditioning and SSR
backplanes for digital signal
conditioning.

NSC68-5050 Non-shielded cable connects from

68-pin VHDCI male connector to
two 50-pin female headers. The
pinout of these headers allows for
direct connection to SSR
backplanes for digital signal
conditioning.

Connects to the following standard
68-pin screw terminal blocks:

• SCB-68

• CB-68LP

• CB-68LPR

•TBX-68

26-pin headers can connect to the
following 5B backplanes for analog
signal conditioning:

• 5B08 (8-channel)

• 5B01 (16-channel)

50-pin header can connect to the
following SSR backplanes for digital
signal conditioning:

• 8-channel backplane

• 16-channel backplane

• 32-channel backplane

50-pin headers can connect to the
following SSR backplanes for digital
signal conditioning:

• 8-channel backplane

• 16-channel backplane

• 32-channel backplane

Refer to Appendix B, Connecting I/O Signals, for more information on
using these cables and accessories to connect I/O signals to the PXI-7831R.
For the most up-to-date cabling options, refer to
the sales office nearest to you.

ni.com/catalog or call

Custom Cabling

NI offers a variety of cables that you can use to connect signals to the
NI PXI-7831R. If you need to develop a custom cable, NI provides a
generic un-terminated shielded cable that makes this task easier. The

NI PXI-7831R User Manual 1-10 ni.com

Unpacking

Caution Never touch the exposed pins of connectors.

Chapter 1 Introduction

SHC68-NT-S (NI part #189041-02) connects to the NI PXI-7831R VHDCI
connectors on one end of the cable. The other end of the cable is not
terminated. This cable ships with a wire list identifying which wire
corresponds to which NI PXI-7831R pin. Using this cable, you can quickly
connect the NI PXI-7831R signals that you need to the connector of your
choice without having to connect these signals to the VHDCI connector
end of the cable. Refer to Appendix B, Connecting I/O Signals for the
NI PXI-7831R connector pinouts.

The RIO device is shipped in an antistatic package to prevent electrostatic
damage (ESD) to the device. ESD can damage several components on the
device.

To avoid such damage in handling the device, take the following
precautions:

• Ground yourself using a grounding strap or by holding a grounded
object.

• Touch the antistatic package to a metal part of the computer chassis
before removing the device from the package.

Remove the device from the package and inspect the device for loose
components or any sign of damage. Notify NI if the device appears
damaged in any way. Do not install a damaged device into the computer.

Store the RIO device in the antistatic envelope when not in use.

Safety Information

The following section contains important safety information that you must
follow when installing and using the NI PXI-7831R.

Do not operate the NI PXI-7831R in a manner not specified in this
document. Misuse of the NI PXI-7831R can result in a hazard. You can
compromise the safety protection built into the NI PXI-7831R if the
NI PXI-7831R is damaged in any way. If the NI PXI-7831R is damaged,
return it to NI for repair.

© National Instruments Corporation 1-11 NI PXI-7831R User Manual

Chapter 1 Introduction

Do not substitute parts or modify the NI PXI-7831R except as described in
this document. Use the NI PXI-7831R only with the chassis, modules,
accessories, and cables specified in the installation instructions. You must
have all covers and filler panels installed during operation of the
NI PXI-7831R.

Do not operate the NI PXI-7831R in an explosive atmosphere or where
there may be flammable gases or fumes. If you must operate the
NI PXI-7831R in such an environment, it must be in a suitably rated
enclosure.

If you need to clean the NI PXI-7831R, use a soft, nonmetallic brush. Make
sure that the NI PXI-7831R is completely dry and free from contaminants
before returning it to service.

Operate the NI PXI-7831R only at or below Pollution Degree 2. Pollution
is foreign matter in a solid, liquid, or gaseous state that can reduce dielectric
strength or surface resistivity. The following is a description of pollution
degrees:

• Pollution Degree 1 means no pollution or only dry, nonconductive
pollution occurs. The pollution has no influence.

• Pollution Degree 2 means that only nonconductive pollution occurs in
most cases. Occasionally, however, a temporary conductivity caused
by condensation must be expected.

• Pollution Degree 3 means that conductive pollution occurs, or dry,
nonconductive pollution occurs that becomes conductive due to
condensation.

You must insulate signal connections for the maximum voltage for which
the NI PXI-7831R is rated. Do not exceed the maximum ratings for the
NI PXI-7831R. Do not install wiring while the NI PXI-7831R is live with
electrical signals. Do not remove or add connector blocks when power is
connected to the system. Remove power from signal lines before
connecting them to or disconnecting them from the NI PXI-7831R.

Operate the NI PXI-7831R at or below the installation category

1

marked

on the hardware label. Measurement circuits are subjected to working

voltages

2

and transient stresses (overvoltage) from the circuit to which they

are connected during measurement or test. Installation categories establish

1

Installation categories, also referred to as measurement categories, are defined in electrical safety standard IEC 61010-1.

2

Working voltage is the highest rms value of an AC or DC voltage that can occur across any particular insulation.

NI PXI-7831R User Manual 1-12 ni.com

Chapter 1 Introduction

standard impulse withstand voltage levels that commonly occur in
electrical distribution systems. The following is a description of installation
categories:

• Installation Category I is for measurements performed on circuits not
directly connected to the electrical distribution system referred to as
MAINS

1

voltage. This category is for measurements of voltages from
specially protected secondary circuits. Such voltage measurements
include signal levels, special equipment, limited-energy parts of
equipment, circuits powered by regulated low-voltage sources, and
electronics.

• Installation Category II is for measurements performed on circuits
directly connected to the electrical distribution system. This category
refers to local-level electrical distribution, such as that provided by a
standard wall outlet (for example, 115 V for U.S. or 230 V for Europe).
Examples of Installation Category II are measurements performed on
household appliances, portable tools, and similar products.

• Installation Category III is for measurements performed in the building
installation at the distribution level. This category refers to
measurements on hard-wired equipment such as equipment in fixed
installations, distribution boards, and circuit breakers. Other examples
are wiring, including cables, bus-bars, junction boxes, switches,
socket-outlets in the fixed installation, and stationary motors with
permanent connections to fixed installations.

• Installation Category IV is for measurements performed at the primary
electrical supply installation (<1,000V). Examples include electricity
meters and measurements on primary overcurrent protection devices
and on ripple control units.

1

MAINS is defined as a hazardous live electrical supply system that powers equipment. Suitably rated measuring circuits may
be connected to the MAINS for measuring purposes.

© National Instruments Corporation 1-13 NI PXI-7831R User Manual

Hardware Overview
of the NI PXI-7831R

This chapter presents an overview of the hardware functions and
I/O connectors on the NI PXI-7831R.

Figure 2-1 shows a block diagram for the NI PXI-7831R, and Figure 2-2
shows the parts locator diagrams for the NI PXI-7831R.

Calibration

Amplifier

x8 Channels

Temperature

Calibration

DACs

DACs

Sensor

AISENSE

AIGND

Connector 0 (MIO)

Input Mode Mux

AI+

AI–

Calibration

Mux

Input Mux

Voltage

Reference

16-Bit

DAC

Digital I/O (16)

+

Instrumentation

–

2

x8 Channels

16-Bit

ADC

User-

Configurable

FPGA

on RIO

Devices

Configuration

Control

Configuration

Data/Address/

Control

Flash

Memory

Bus

Interface

PXI Local Bus

RTSI Bus

2

Control

Address/Data

PXI/CompactPCI Bus

Digital I/O (40)

Connector 1 (DIO)

Digital I/O (40)

Connector 2 (DIO)

Figure 2-1. NI PXI-7831R Block Diagram

© National Instruments Corporation 2-1 NI PXI-7831R User Manual