Important Information
Warranty
The NI 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
in materials and workmanship, for a period of 90 days from date of shipment, as evidenced by receipts or other documentation. National
Instruments will, at its option, repair or replace software media that do not execute programming instructions if National Instruments receives
notice of such defects during the warranty period. National Instruments does not warrant that the operation of the software shall be
uninterrupted or error free.
A Return Material Authorization (RMA) number must be obtained from the factory and clearly marked on the outside of the package 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 believes that the information in this document is accurate. The document has been carefully reviewed for technical
accuracy. In the event that technical or typographical errors exist, National Instruments reserves the right to make changes to subsequent
editions of this document without prior notice to holders of this edition. The reader should consult National Instruments if errors are suspected.
In no event shall National Instruments be liable for any damages arising out of or related to this document or the information contained in it.
EXCEPT AS SPECIFIED HEREIN, NATIONAL INSTRUMENTS MAKES NO WARRANTIES, EXPRESS OR IMPLIED, AND SPECIFICALLY DISCLAIMS ANY WARRANTY OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. CUSTOMER’S RIGHT TO RECOVER DAMAGES CAUSED BY FAULT OR NEGLIGENCE ON THE PART OF
NATIONAL INSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER. NATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR
DAMAGES RESULTING FROM LOSS OF DATA, PROFITS, USE OF PRODUCTS, OR INCIDENTAL OR CONSEQUENTIAL DAMAGES, EVEN IF ADVISED OF THE POSSIBILITY
THEREOF. This limitation of the liability of National Instruments will apply regardless of the form of action, whether in contract or tort, including
negligence. Any action against National Instruments must be brought within one year after the cause of action accrues. National Instruments
shall not be liable for any delay in performance due to causes beyond its reasonable control. The warranty provided herein does not cover
damages, defects, malfunctions, or service failures caused by owner’s failure to follow the National Instruments installation, operation, or
maintenance instructions; owner’s modification of the product; owner’s abuse, misuse, or negligent acts; and power failure or surges, fire,
flood, accident, actions of third parties, or other events outside reasonable control.
Copyright
Under the copyright laws, this publication may not be reproduced or transmitted in any form, electronic or mechanical, including photocopying,
recording, storing in an information retrieval system, or translating, in whole or in part, without the prior written consent of National
Instruments Corporation.
Trademarks
CompactRIO™, LabVIEW™, National Instruments™, NI™, ni.com™, NI Developer Zone™, and RTSI™ are trademarks of National Instruments
Corporation.
Product and company names mentioned herein are trademarks or trade names of their respective companies.
Patents
For patents covering National Instruments products, refer to the appropriate location: Help»Patents in your software, the patents.txtfile
on your CD, or ni.com/patents.
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 RISK OF BODILY INJURY AND DEATH) SHOULD
NOT BE RELIANT SOLELY UPON ONE FORM OF ELECTRONIC SYSTEM DUE TO THE RISK OF SYSTEM FAILURE. TO AVOID
DAMAGE, INJURY, OR DEATH, THE USER OR APPLICATION DESIGNER MUST TAKE REASONABLY PRUDENT STEPS TO
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 NATIONAL INSTRUMENTS' TESTING
PLATFORMS AND BECAUSE A USER OR APPLICATION 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.
Download from Www.Somanuals.com. All Manuals Search And Download.
Compliance
Compliance with FCC/Canada Radio Frequency Interference
Regulations
Determining FCC Class
The Federal Communications Commission (FCC) has rules to protect wireless communications from interference. The FCC
places digital electronics into two classes. These classes are known as Class A (for use in industrial-commercial locations only)
or Class B (for use in residential or commercial locations). All National Instruments (NI) products are FCC Class A products.
Depending on where it is operated, this Class A product could be subject to restrictions in the FCC rules. (In Canada, the
Department of Communications (DOC), of Industry Canada, regulates wireless interference in much the same way.) Digital
electronics emit weak signals during normal operation that can affect radio, television, or other wireless products.
All Class A products display a simple warning statement of one paragraph in length regarding interference and undesired
operation. The FCC rules have restrictions regarding the locations where FCC Class A products can be operated.
FCC/DOC Warnings
This equipment generates and uses radio frequency energy and, if not installed and used in strict accordance with the instructions
in this manual and the CE marking Declaration of Conformity*, may cause interference to radio and television reception.
Classification requirements are the same for the Federal Communications Commission (FCC) and the Canadian Department
of Communications (DOC).
Changes or modifications not expressly approved by NI could void the user’s authority to operate the equipment under the
FCC Rules.
Class A
Federal Communications Commission
This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part 15 of the FCC
Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated
in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and
used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this
equipment in a residential area is likely to cause harmful interference in which case the user is required to correct the interference
at their own expense.
Canadian Department of Communications
This Class A digital apparatus meets all requirements of the Canadian Interference-Causing Equipment Regulations.
Cet appareil numérique de la classe A respecte toutes les exigences du Règlement sur le matériel brouilleur du Canada.
Compliance with EU Directives
Users in the European Union (EU) should refer to the Declaration of Conformity (DoC) for information* pertaining to the
CE marking. Refer to the Declaration of Conformity (DoC) for this product for any additional regulatory compliance
information. To obtain the DoC for this product, visit ni.com/hardref.nsf, search by model number or product line,
and click the appropriate link in the Certification column.
*
The CE marking Declaration of Conformity contains important supplementary information and instructions for the user or
installer.
Download from Www.Somanuals.com. All Manuals Search And Download.
About This Manual
Conventions ...................................................................................................................vii
Chapter 1
Reconfigurable I/O Architecture.....................................................................1-4
Software Development ..................................................................................................1-5
LabVIEW FPGA Module................................................................................1-5
LabVIEW Real-Time Module.........................................................................1-6
Cables and Optional Equipment ....................................................................................1-7
Chapter 2
Connecting Analog Input Signals..................................................................................2-5
Types of Signal Sources ................................................................................................2-7
Floating Signal Sources...................................................................................2-7
Ground-Referenced Signal Sources ................................................................2-7
Input Modes ...................................................................................................................2-7
Differential Connection Considerations (DIFF Input Mode)..........................2-9
Differential Connections for Ground-Referenced Signal Sources....2-9
Differential Connections for Nonreferenced
or Floating Signal Sources .............................................................2-10
© National Instruments Corporation
v
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Contents
Connecting Analog Output Signals............................................................................... 2-15
Connecting Digital I/O Signals ..................................................................................... 2-16
RTSI Trigger Bus .......................................................................................................... 2-19
Switch Settings.............................................................................................................. 2-21
Chapter 3
Loading Calibration Constants...................................................................................... 3-1
Internal Calibration........................................................................................................ 3-1
External Calibration....................................................................................................... 3-2
Appendix A
Specifications
Appendix B
Connecting I/O Signals
Appendix C
Appendix D
Technical Support and Professional Services
Glossary
NI 7831R User Manual
vi
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
About This Manual
This manual describes the electrical and mechanical aspects of the
National Instruments 7831R device and contains information concerning
its operation and programming.
The NI 7831R device is a Reconfigurable I/O (RIO) device. The NI 7831R
has 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 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
About This Manual
programs, subprograms, subroutines, device names, functions, operations,
variables, filenames, and extensions.
Reconfigurable I/O Documentation
The NI 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. The documentation includes the following documents:
•
•
Getting Started with the NI 7831R—This document lists what you
need to get started, describes how to unpack and install the hardware
and software, and contains information about connecting I/O signals to
the NI 7831R.
LabVIEW FPGA Module Release Notes—This document contains
information about installing and getting started with the
LabVIEW FPGA Module. Select Start»Program Files»National
Instruments»<LabVIEW>»Module Documents»LabVIEW
FPGA»Release Notes to view this document.
•
•
LabVIEW FPGA Module User Manual—This manual describes how
to use the LabVIEW FPGA Module to create virtual instruments (VIs)
that run on the NI 7831R. Select Start»Program Files»National
Instruments»<LabVIEW>»Module Documents»FPGA User
Interface to view this document.
FPGA Interface User Guide—This manual describes how to control
and communicate with FPGA VIs running on R Series devices. Select
Start»Program Files»National Instruments»<LabVIEW>»
Module Documents»LabVIEW FPGA»LabVIEW FPGA Module
User Manual to view this document.
•
•
LabVIEW Help—This help file contains information about using the
LabVIEW FPGA Module, LabVIEW, and the LabVIEW Real-Time
Module with the NI 7831R. Select Help»VI, Function, & How-To
Help in LabVIEW to view the LabVIEW Help.
LabVIEW Real-Time Module User Manual—This manual contains
information about how to build deterministic applications using the
LabVIEW Real-Time Module.
NI 7831R User Manual
viii
Download from Www.Somanuals.com. All Manuals Search And Download.
ni.com
About This Manual
Related Documentation
The following documents contain information you might find helpful:
•
NI Developer Zone tutorial, Field Wiring and Noise Considerations
for Analog Signals, at ni.com/zone
•
•
•
PICMG CompactPCI 2.0 R3.0
PXI Hardware Specification Revision 2.1
PXI Software Specification Revision 2.1
© National Instruments Corporation
ix
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
1
Introduction
This chapter describes the NI 7831R, describes the concept of the
Reconfigurable I/O device, describes the optional software and equipment,
and contains information about the NI 7831R.
About the NI 7831R
The NI 7831R is an R Series device with 96 digital I/O (DIO) lines, eight
independent, 16-bit analog output (AO) channels, and eight independent,
16-bit analog input (AI) channels.
A user-reconfigurable FPGA (Field-Programmable Gate Array) controls
the digital and analog I/O lines on the NI 7831R. The FPGA on the R Series
device allows you to define the functionality and timing of the device. You
can change the functionality of the FPGA on the R Series device in
LabVIEW using the LabVIEW FPGA Module to create and download a
custom virtual instrument (VI) to the FPGA. Using the FPGA Module, you
can graphically design the timing and functionality of the R Series device.
If you only have LabVIEW but not the FPGA Module, you cannot create
new FPGA VIs, but you can create VIs that run on Windows or an RT target
to control existing FPGA VIs.
Some applications require tasks such as real-time, floating-point
processing or datalogging while performing I/O and logic on the R Series
device. You can use the LabVIEW Real-Time Module to perform these
additional applications while communicating with and controlling the
R Series device.
The R Series device contains flash memory to store VIs for automatic
loading of the FPGA when the system is powered on.
The NI 7831R device uses the Real-Time System Integration (RTSI) bus to
easily synchronize several measurement functions to a common trigger or
timing event. The PXI chassis can accommodate multiple devices. The
NI PCI-7831R accesses the RTSI bus through a RTSI cable connected
© National Instruments Corporation
1-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
between devices. The NI PXI-7831R accesses the RTSI bus through the
PXI trigger lines implemented on the PXI backplane.
Refer to Appendix A, Specifications, for detailed NI 7831R specifications.
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 still can use the basic plug-in card
functions. For example, the RTSI bus on the R Series 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
The standard implementation for CompactPCI does not include these
sub-buses. The R Series device works in any standard CompactPCI chassis
adhering to the PICMG CompactPCI 2.0 R3.0 core specification.
PXI-specific features are implemented on the J2 connector of the
CompactPCI bus. Table 1-1 lists the J2 pins used by the NI 7831R. The
NI 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 R Series 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 7831R User Manual
1-2
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
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 Star Trigger
LBLSTAR<0..12>
PXI Clock 10 MHz
PXI Star Trigger
LBL<0..12>
E17
D17
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
Overview of Reconfigurable I/O
This section explains reconfigurable I/O and describes how to use the
FPGA Module to build high-level functions in hardware.
Refer to Chapter 2, Hardware Overview of the NI 7831R, for descriptions
of the I/O resources on the NI 7831R.
Reconfigurable I/O Concept
The NI 7831R is based on a reconfigurable FPGA core surrounded by fixed
I/O resources for analog and digital input and output. You can configure
the behavior of the reconfigurable core to match the requirements of the
measurement and control system. You can implement this user-defined
behavior as an FPGA VI to create an application-specific I/O device.
Flexible Functionality
Flexible functionality allows the NI 7831R to match individual application
requirements and to mimic the functionality of fixed I/O devices. For
example, you can configure a R Series device in one application for three
32-bit quadrature encoders and then reconfigure the R Series device in
another application for eight 16-bit event counters.
You also can use the R Series device in timing and triggering applications
with the LabVIEW Real-Time Module, such as control and
hardware-in-the-loop (HIL) simulations. For example, you can configure
the R Series 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
1-3
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
User-Defined I/O Resources
You can create your own custom measurements using the 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 after an
analog input exceeds a programmable threshold.
Device-Embedded Logic and Processing
You can implement LabVIEW logic and processing in the FPGA of the
R Series device. Typical logic functions include Boolean operations,
comparisons, and basic mathematical operations. You can implement
in parallel. You can implement more complex algorithms such as control
loops. You are limited only by the size of the FPGA.
Reconfigurable I/O Architecture
Figure 1-1 shows an FPGA connected to fixed I/O resources and a bus
interface. The fixed I/O resources include A/D converters (ADCs), D/A
converters (DACs), and digital I/O lines.
Fixed I/O Resource
Fixed I/O Resource
FPGA
Fixed I/O Resource
Fixed I/O Resource
Bus Interface
Figure 1-1. High-Level FPGA Functional Overview
Software accesses the R Series device through the bus interface, and the
FPGA connects the bus interface and the fixed I/O to make possible timing,
triggering, processing, and custom I/O functions using the LabVIEW
FPGA Module.
NI 7831R User Manual
1-4
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
The FPGA logic provides timing, triggering, processing, and custom I/O
measurements. Each fixed I/O resource used by the application uses a small
portion of the FPGA logic that controls the fixed I/O resource. The bus
interface also uses 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. The functions use varied amounts of logic.
You can place useful applications in the FPGA. How much FPGA space
your application requires depends on your need for I/O recovery, I/O, and
logic algorithms.
The FPGA does not retain the VI when it is powered off, so you must reload
the VI each time you power on. You can load the VI from onboard flash
memory or from 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 Module User Manual for more
information about how to store your VI in flash memory.
Reconfigurable I/O Applications
You can use the LabVIEW FPGA Module to create or acquire new VIs for
your application. The FPGA Module allows you to define custom
functionality for the R Series device using a subset of LabVIEW
functionality. Refer to the FPGA Module examples located in the
<LabVIEW>\examples\FPGAdirectory for examples of FPGA VIs.
Software Development
You can use LabVIEW with the LabVIEW FPGA Module to program the
NI 7831R. To develop real-time applications that control the NI 7831R,
you can use LabVIEW with the LabVIEW Real-Time Module.
LabVIEW FPGA Module
The FPGA Module enables you to use LabVIEW to create VIs that run on
the FPGA of the R Series device. Use the FPGA Module VIs and functions
to control the I/O, timing, and logic of the R Series device and to generate
Guide, available by selecting Start»Program Files»National
Instruments»<LabVIEW>»Module Documents»FPGA Interface User
Guide, for information about the FPGA Interface functions.
© National Instruments Corporation
1-5
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
You can use Interactive Front Panel Communication to communicate
directly with the VI running on the FPGA. You can use Programmatic
FPGA Interface Communication to programmatically control and
communicate with FPGA VIs from host VIs.
Use the FPGA Interface functions when you target LabVIEW for Windows
or an RT target to create host VIs that wait for interrupts and control the
FPGA by reading and writing the FPGA VI running on the R Series device.
Note If you use the R Series device without the FPGA Module, you can use the Download
VI or Attributes to Flash Memory utility available by selecting Start»Program Files»
National Instruments»NI-RIO to download precomplied FPGA VIs to the flash memory
of the R Series device. This utility is installed by the NI-RIO CD. You also can use the
utility to configure the analog input mode, to synchronize the clock R Series device to the
PXI clock (for NI PXI-7831R only), and to configure when the VI loads from flash
memory.
LabVIEW Real-Time Module
The LabVIEW Real-Time Module extends the LabVIEW development
environment to deliver deterministic, real-time performance.
You can write host VIs that run in Windows or on RT targets to
communicate with FPGA VIs that run on the NI 7831R. You can develop
Real-Time VIs with LabVIEW and the LabVIEW Real-Time Module, and
then download the VIs to run on a hardware target with a real-time
operating system. The LabVIEW Real-Time Module allows you to use the
NI 7831R in RT Series PXI systems being controlled in real time by a VI.
The NI 7831R plug-in device is designed as a single-point AI, AO, and DIO
complement to the LabVIEW Real-Time Module. Refer to the LabVIEW
Real-Time Module User Manual and the LabVIEW Help, available by
selecting Help»VI, Function, & How-To Help, for more information
about the LabVIEW Real-Time Module.
NI 7831R User Manual
1-6
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
Cables and Optional Equipment
National Instruments offers a variety of products you can use with R Series
devices, including cables, connector blocks, and other accessories, as
shown in Table 1-2.
Table 1-2. Cables and Accessories
NI 7831R
Cable
Cable Description
Connector
Accessories
SH68-C68-S
Shielded 68-pin VHDCI
male connector to female
0.050 series D-type
MIO or DIO Connects to the following
standard 68-pin screw
terminal blocks:
connector. The cable is
constructed with 34 twisted
wire pairs and an overall
shield.
• SCB-68
• CB-68LP
• CB-68LPR
• TBX-68
SMC68-68-RMIO
Shielded 68-pin VHDCI
male connector to female
0.050 series D-type
MIO only
Connects to the following
standard 68-pin screw
terminal blocks:
connector. The cable is
constructed with individually
shielded twisted-pairs for the
analog input channels plus an
additional shield around all
the analog signals. This cable
provides superior noise
immunity on the MIO
connector.
• SCB-68
• CB-68LP
• CB-68LPR
• TBX-68
© National Instruments Corporation
1-7
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
Table 1-2. Cables and Accessories (Continued)
NI 7831R
Cable
NSC68-262650
Cable Description
Connector
Accessories
Non-shielded cable connects MIO only
from 68-pin VHDCI male
connector to two 26-pin
26-pin headers can connect
to the following 5B
backplanes for analog signal
conditioning:
female headers plus one
50-pin female header. The
pinout of these headers
• 5B08 (8-channel)
• 5B01 (16-channel)
allows for direct connection
to 5B backplanes for analog
signal conditioning and SSR
backplanes for digital signal
conditioning.
50-pin header can connect to
the following SSR
backplanes for digital signal
conditioning:
• 8-channel backplane
• 16-channel backplane
• 32-channel backplane
NSC68-5050
Non-shielded cable connects DIO only
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.
50-pin headers can connect
to the following SSR
backplanes for digital signal
• 8-channel backplane
• 16-channel backplane
• 32-channel backplane
Refer to Appendix B, Connecting I/O Signals, for more information about
using these cables and accessories to connect I/O signals to the NI 7831R.
Refer to ni.com/catalogfor the most current cabling options.
Custom Cabling
NI offers a variety of cables for connecting signals to the NI 7831R. If you
need to develop a custom cable, a nonterminated shielded cable is available
from NI. The SHC68-NT-S connects to the NI 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 the wires that correspond to each
NI 7831R pin. Using this cable, you can quickly connect the NI 7831R
signals that you need to the connector of your choice. Refer to Appendix B,
Connecting I/O Signals, for the NI 7831R connector pinouts.
NI 7831R User Manual
1-8
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
Safety Information
The following section contains important safety information that you must
follow when installing and using the NI 7831R.
Do not operate the NI 7831R in a manner not specified in this document.
Misuse of the NI 7831R can result in a hazard. You can compromise the
safety protection built into the NI 7831R if the NI 7831R is damaged in any
way. If the NI 7831R is damaged, return it to NI for repair.
Do not substitute parts or modify the NI 7831R except as described in this
document. Use the NI 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 7831R.
Do not operate the NI 7831R in an explosive atmosphere or where there
might be flammable gases or fumes. If you must operate the NI 7831R in
such an environment, it must be in a suitably rated enclosure.
If you need to clean the NI 7831R, use a soft, nonmetallic brush. Make sure
that the NI 7831R is completely dry and free from contaminants before
returning it to service.
Operate the NI 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—No pollution or only dry, nonconductive
pollution occurs. The pollution has no influence.
•
Pollution Degree 2—Only nonconductive pollution occurs in most
cases. Occasionally, however, a temporary conductivity caused by
condensation can be expected.
•
Pollution Degree 3—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 7831R is rated. Do not exceed the maximum ratings for the
NI 7831R. Do not install wiring while the NI 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 7831R.
© National Instruments Corporation
1-9
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 1
Introduction
Operate the NI 7831R at or below the installation category1 listed in the
section Maximum working voltage, in Appendix A, Specifications.
Measurement circuits are subjected to working voltages2 and transient
stresses (overvoltage) from the circuit to which they are connected during
measurement or test. Installation categories establish standard impulse
withstand voltage levels that commonly occur in electrical distribution
systems. The following list describes installation categories:
•
Installation Category I—Measurements performed on circuits not
directly connected to the electrical distribution system referred to as
MAINS3 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—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—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—Measurements performed at the primary
electrical supply installation (<1,000 V). Examples include electricity
meters and measurements on primary overcurrent protection devices
and on ripple control units.
1
Installation categories, also referred to as measurement categories, are defined in electrical safety standard IEC 61010-1.
2
3
Working voltage is the highest rms value of an AC or DC voltage that can occur across any particular insulation.
MAINS is defined as a hazardous live electrical supply system that powers equipment. Suitably rated measuring circuits can
be connected to the MAINS for measuring purposes.
NI 7831R User Manual
1-10
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
2
Hardware Overview
of the NI 7831R
This chapter presents an overview of the hardware functions and
I/O connectors on the NI 7831R.
Figure 2-1 shows a block diagram for the NI 7831R. Figure 2-2 shows the
parts locator diagram for the NI PXI-7831R. Figure 2-3 shows the parts
locator diagram for the NI PCI-7831R.
Calibration
DACs
Configuration
Control
Flash
Memory
Input Mux
AI+
AI–
+
16-Bit
ADC
Instrumentation
Amplifier
–
x8 Channels
Input Mode Mux
AISENSE
AIGND
User-
Voltage
Temperature
Sensor
Control
Reference
Bus
Interface
Configurable
FPGA on RIO
Devices
Data/Address/
Control
Calibration
Mux
Address/Data
2
Calibration
DACs
16-Bit
DAC
x8 Channels
Digital I/O (16)
Digital I/O (40)
PXI Local Bus (NI PXI-7831R only)
RTSI Bus
Digital I/O (40)
Figure 2-1. NI 7831R Block Diagram
© National Instruments Corporation
2-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
SW1
Figure 2-3. Parts Locator Diagram for the NI PCI-7831R
Analog Input
The NI 7831R has eight independent, 16-bit AI channels that you
can sample simultaneously or at different rates. The input mode is
software-configurable, and the input range is fixed at 10 V. The
converters return data in two’s complement format. Table 2-1 shows the
ideal output code returned for a given AI voltage.
© National Instruments Corporation
2-3
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Table 2-1. Ideal Output Code and AI Voltage Mapping
Output Code (Hex)
(Two’s Complement)
Input Description
AI Voltage
9.999695
Full-scale range –1 LSB
Full-scale range –2 LSB
Midscale
7FFF
7FFE
0000
8001
8000
—
9.999390
0.000000
Negative full-scale range +1 LSB
Negative full-scale range
Any input voltage
–9.999695
–10.000000
Output Code
---------------------------------
× 10.0 V
32,768
Input Modes
The NI 7831R input mode is software configurable. The input channels
support three input modes—differential (DIFF), referenced single-ended
(RSE), and nonreferenced single-ended (NRSE). The selected input mode
applies to all the input channels. Table 2-2 describes the three input modes.
Table 2-2. Available Input Modes for the NI 7831R
Input Mode
Description
DIFF
When the NI 7831R is configured in DIFF input mode, each channel uses two
AI lines. The positive input pin connects to the positive terminal of the onboard
instrumentation amplifier. The negative input pin connects to the negative input
of the instrumentation amplifier.
RSE
When the NI 7831R is configured in RSE input mode, each channel uses only its
positive AI pin. This pin connects to the positive terminal of the onboard
instrumentation amplifier. The negative input of the instrumentation amplifier
connects internally to the AI ground (AIGND).
NRSE
When the NI 7831R is configured in NRSE input mode, each channel uses only
its positive AI pin. This pin connects to the positive terminal of the onboard
instrumentation amplifier. The negative input of the instrumentation amplifier on
each AI channel connects internally to the AISENSE input pin.
The NI 7831R AI range is fixed at 10 V.
NI 7831R User Manual
2-4
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Connecting Analog Input Signals
The AI signals for the NI 7831R are AI<0..7>+, AI<0..7>–, AIGND, and
AISENSE. The AI<0..7>+ and AI<0..7>– signals are connected to the
eight AI channels of the NI 7831R. For all input modes, the AI<0..7>+
signals are connected to the positive input of the instrumentation amplifier
on each channel. The signal connected to the negative input of the
instrumentation amplifier depends on how you configure the input mode of
the device.
In differential input mode, signals connected to AI<0..7>– are routed to the
negative input of the instrumentation amplifier for each channel. In RSE
input mode, the negative input of the instrumentation amplifier for each
channel is internally connected to AIGND. In NRSE input mode, the
AISENSE signal is connected internally to the negative input of the
instrumentation amplifier for each channel. In DIFF and RSE input modes,
AISENSE is not used.
Caution Exceeding the differential and common-mode input ranges distorts the input
signals. Exceeding the maximum input voltage rating can damage the NI 7831R and the
computer. NI is not liable for any damage resulting from such signal connections. The
maximum input voltage ratings are listed in Table B-2, NI 7831R I/O Signal Summary.
AIGND is a common AI signal that is routed directly to the ground tie point
point to the NI 7831R if necessary.
Connection of AI signals to the NI 7831R depends on the input mode of the
AI channels you are using and the type of input signal source. With
different input modes, you can use the instrumentation amplifier in
different ways. Figure 2-4 shows a diagram of the NI 7831R
instrumentation amplifier.
© National Instruments Corporation
2-5
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Vin+
+
Instrumentation
Amplifier
+
Measured
Voltage
Vm
–
Vin–
–
Vm = [Vin+ – Vin–]
Figure 2-4. NI 7831R Instrumentation Amplifier
The instrumentation amplifier applies common-mode voltage rejection
and presents high input impedance to the AI signals connected to the
NI 7831R. Input multiplexers on the device route signals to the positive and
negative inputs of the instrumentation amplifier. The instrumentation
amplifier converts two input signals to a signal that is the difference
between the two input signals. The amplifier output voltage is referenced to
the device ground. The NI 7831R ADC measures this output voltage when
it performs A/D conversions.
You must reference all signals to ground either at the source device or at the
NI 7831R. If you have a floating source, reference the signal to ground by
using RSE input mode or the DIFF input mode with bias resistors. Refer to
the Differential Connections for Nonreferenced or Floating Signal Sources
section of this chapter for more information about these input modes. If you
have a grounded source, do not reference the signal to AIGND. You can
avoid this reference by using DIFF or NRSE input modes.
NI 7831R User Manual
2-6
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Types of Signal Sources
When configuring the input channels and making signal connections,
you must first determine whether the signal sources are floating or ground
referenced. The following sections describe these two signal types.
Floating Signal Sources
A floating signal source is not connected to the building ground system but
instead has an isolated ground-reference point. Some examples of floating
signal sources are outputs of transformers, thermocouples, battery-powered
devices, optical isolator outputs, and isolation amplifiers. An instrument or
device that has an isolated output is a floating signal source. You must
connect the ground reference of a floating signal to the NI 7831R AIGND
through a bias resistor to establish a local or onboard reference for the
signal. Otherwise, the measured input signal varies as the source floats out
of the common-mode input range.
Ground-Referenced Signal Sources
A ground-referenced signal source is connected to the building system
ground, so it is already connected to a common ground point with respect
to the NI 7831R, assuming that the computer is plugged into the same
power system. Instruments or devices with nonisolated outputs that plug
into the building power system are ground referenced signal sources.
The difference in ground potential between two instruments connected to
the same building power system is typically between 1 and 100 mV. This
difference can be much higher if power distribution circuits are improperly
connected. If a grounded signal source is improperly measured, this
difference might appear as a measurement error. The connection
instructions for grounded signal sources are designed to eliminate this
ground potential difference from the measured signal.
Input Modes
The following sections discuss single-ended and differential measurements
and considerations for measuring both floating and ground-referenced
signal sources.
Figure 2-5 summarizes the recommended input mode for both types of
signal sources.
© National Instruments Corporation
2-7
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Signal Source Type
Floating Signal Source
Grounded Signal Source
(Not Connected to Building Ground)
Examples
Examples
• Ungrounded Thermocouples
• Signal Conditioning with
Isolated Outputs
• Plug-in Instruments with
Nonisolated Outputs
Input
• Battery Devices
AI<i>(+)
AI<i>(+)
+
+
+
–
+
–
V1
V1
AI<i>(–)
AI<i>(–)
–
–
Differential
(DIFF)
AIGND<i>
AIGND<i>
See text for information on bias resistors.
NOT RECOMMENDED
AI<i>
AI
+
+
+
–
+
–
V1
V1
AIGND<i>
–
–
Single-Ended —
Ground
+
V
–
g
Referenced
(RSE)
AIGND
Ground-loop losses, Vg, are added to
measured signal.
AI<i>
AI<i>
+
+
+
–
+
–
V1
V1
AISENSE
AISENSE
–
–
Single-Ended —
Nonreferenced
(NRSE)
AIGND<i>
AIGND<i>
See text for information on bias resistors.
Figure 2-5. Summary of Analog Input Connections
NI 7831R User Manual
2-8
Download from Www.Somanuals.com. All Manuals Search And Download.
ni.com
Chapter 2
Hardware Overview of the NI 7831R
Differential Connection Considerations (DIFF Input Mode)
In DIFF input mode, the NI 7831R measures the difference between the
positive and negative inputs. DIFF input mode is ideal for measuring
ground-referenced signals from other devices. When using DIFF input
mode, the input signal connects to the positive input of the instrumentation
amplifier and its reference signal, or return, connects to the negative input
of the instrumentation amplifier.
Use differential input connections for any channel that meets any of the
following conditions:
•
•
The input signal is low-level (less than 1 V).
The leads connecting the signal to the NI 7831R are greater than
3 m (10 ft).
•
•
The input signal requires a separate ground-reference point or return
signal.
The signal leads travel through noisy environments.
Differential signal connections reduce noise pickup and increase
common-mode noise rejection. Differential signal connections also allow
instrumentation amplifier.
Differential Connections for Ground-Referenced
Signal Sources
Figure 2-6 shows how to connect a ground-referenced signal source to a
channel on the NI 7831R configured in DIFF input mode.
© National Instruments Corporation
2-9
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
AI+
+
Ground-
Referenced
Signal
+
–
AI–
Instrumentation
Amplifier
Vs
+
–
Source
Measured
Voltage
Vm
–
Common-
Mode
Noise and
Ground
+
–
Vcm
x8 Channels
AISENSE
AIGND
Potential
I/O Connector
DIFF Input Mode Selected
Figure 2-6. Differential Input Connections for Ground-Referenced Signals
With this connection type, the instrumentation amplifier rejects both the
between the signal source and the NI 7831R ground, shown as Vcm
in Figure 2-6. In addition, the instrumentation amplifier can reject
common-mode noise pickup in the leads connecting the signal sources to
the device. The instrumentation amplifier can reject common-mode signals
when V+in and V–in (input signals) are both within their specified input
input ranges.
Differential Connections for Nonreferenced or
Floating Signal Sources
Figure 2-7 shows how to connect a floating signal source to a channel on
the NI 7831R configured in DIFF input mode.
NI 7831R User Manual
2-10
Download from Www.Somanuals.com. All Manuals Search And Download.
ni.com
Chapter 2
Hardware Overview of the NI 7831R
AI+
AI–
+
Bias
Resistors
(see text)
+
–
Floating
Signal
Source
Instrumentation
Amplifier
Vs
+
–
Measured
Voltage
Vm
–
Bias
Current
Return
Paths
x8 Channels
AISENSE
AIGND
I/O Connector
DIFF Input Mode Selected
Figure 2-7. Differential Input Connections for Nonreferenced Signals
Figure 2-7 shows two bias resistors connected in parallel with the signal
leads of a floating signal source. If you do not use the resistors and the
source is truly floating, the source might not remain within the
common-mode signal range of the instrumentation amplifier, causing
erroneous readings. You must reference the source to AIGND by
connecting the positive side of the signal to the positive input of the
instrumentation amplifier and connecting the negative side of the signal to
AIGND and to the negative input of the instrumentation amplifier without
resistors. This connection works well for DC-coupled sources with low
source impedance, less than 100 Ω.
For larger source impedances, this connection leaves the differential signal
path significantly out of balance. Noise that couples electrostatically onto
the positive line does not couple onto the negative line because it is
connected to ground. Hence, this noise appears as a differential-mode
signal instead of a common-mode signal, and the instrumentation amplifier
does not reject it. In this case, instead of directly connecting the negative
line to AIGND, connect it to AIGND through a resistor that is about 100
times the equivalent source impedance. The resistor puts the signal path
nearly in balance. About the same amount of noise couples onto both
connections, which yields better rejection of electrostatically coupled
noise. Also, this input mode does not load down the source, other than the
very high-input impedance of the instrumentation amplifier.
© National Instruments Corporation
2-11
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
You can fully balance the signal path by connecting another resistor of the
same value between the positive input and AIGND, as shown in Figure 2-7.
This fully balanced input mode offers slightly better noise rejection but has
the disadvantage of loading down the source with the series combination
(sum) of the two resistors. If, for example, the source impedance is 2 kΩ
and each of the two resistors is 100 kΩ, the resistors load down the source
with 200 kΩ and produce a –1% gain error.
Both inputs of the instrumentation amplifier require a DC path to ground
for the instrumentation amplifier to work. If the source is AC coupled
(capacitively coupled), the instrumentation amplifier needs a resistor
between the positive input and AIGND. If the source has low-impedance,
choose a resistor that is large enough not to significantly load the source but
small enough not to produce significant input offset voltage as a result of
input bias current, typically 100 kΩ to 1 MΩ. In this case, connect the
negative input directly to AIGND. If the source has high output impedance,
balance the signal path as previously described using the same value
resistor on both the positive and negative inputs. Loading down the source
causes some gain error.
Single-Ended Connection Considerations
When the NI 7831R AI signal is referenced to a ground that can be shared
with other input signals, it forms a single-ended connection. The input
signal connects to the positive input of the instrumentation amplifier and
the ground connects to the negative input of the instrumentation amplifier.
You can use single-ended input connections for any input signal that meets
the following conditions:
•
•
The input signal is high-level (>1 V).
The leads connecting the signal to the NI 7831R are less than
3 m (10 ft).
•
The input signal can share a common reference point with other
signals.
Use DIFF input connections for greater signal integrity for any input signal
that does not meet the preceding conditions.
You can configure in software the NI 7831R channels for RSE or NRSE
input modes. Use the RSE input mode for floating signal sources. In this
case, the NI 7831R provides the reference ground point for the external
signal. Use the NRSE input mode for ground-referenced signal sources. In
this case, the external signal supplies its own reference ground point and the
NI 7831R should not supply one.
NI 7831R User Manual
2-12
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
In single-ended input modes, electrostatic and magnetic noise couples into
the signal connections more than in differential input modes. The coupling
is the result of differences in the signal path. Magnetic coupling
is proportional to the area between the two signal conductors. Electrical
two conductors.
Single-Ended Connections for Floating Signal
Sources (RSE Input Mode)
Figure 2-8 shows how to connect a floating signal source to a channel on
the NI 7831R configured for RSE input mode.
AI+
AI–
+
Instrumentation
Amplifier
+
–
Measured
Voltage
–
Vm
+
–
Floating
Signal
Source
Vs
x8 Channels
AISENSE
AIGND
I/O Connector
RSE Input Mode Selected
Figure 2-8. Single-Ended Input Connections for Nonreferenced or Floating Signals
Single-Ended Connections for Grounded Signal
Sources (NRSE Input Mode)
To measure a grounded signal source with a single-ended input mode, you
must configure the NI 7831R in the NRSE input mode. Then connect the
signal to the positive input of the NI 7831R instrumentation amplifier and
connect the signal local ground reference to the negative input of the
instrumentation amplifier. The ground point of the signal should be
connected to AISENSE. Any potential difference between the NI 7831R
ground and the signal ground appears as a common-mode signal at both the
© National Instruments Corporation
2-13
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
positive and negative inputs of the instrumentation amplifier. The
instrumentation amplifier rejects this difference. If the input circuitry of a
NI 7831R is referenced to ground in RSE input mode, this difference in
ground potentials appears as an error in the measured voltage.
Figure 2-9 shows how to connect a grounded signal source to a channel on
the NI 7831R configured for NRSE input mode.
AI+
AI–
+
Ground-
Referenced
Signal
+
–
Instrumentation
Amplifier
Vs
+
–
Source
Measured
Voltage
–
Vm
Common-
Mode
Noise and
Ground
+
–
x8 Channels
Vcm
AISENSE
AIGND
Potential
I/O Connector
Figure 2-9. Single-Ended Input Connections for Ground-Referenced Signals
Common-Mode Signal Rejection Considerations
Figures 2-6 and 2-9 show connections for signal sources that are already
referenced to some ground point with respect to the NI 7831R. In these
ground potential differences between the signal source and the device.
With differential input connections, the instrumentation amplifier can
reject common-mode noise pickup in the leads connecting the signal
sources to the device. The instrumentation amplifier can reject
common-mode signals when V+in and V–in (input signals) are both within
their specified input ranges. Refer to Appendix A, Specifications, for more
information about input ranges.
NI 7831R User Manual
2-14
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Analog Output
The NI 7831R has eight 16-bit AO channels. The bipolar output range is
fixed at 10 V. Some applications require that the AO channels power on
to known voltage levels. To set the power-on levels, you can configure the
NI 7831R to load and run your VI when the system powers on. This VI can
set the AO channels to the desired voltage levels. The VI interprets data
written to the DAC in two’s complement format. Table 2-3 shows the ideal
AO voltage generated for a given input code.
Table 2-3. Ideal Output Voltage and Input Code Mapping
Input Code (Hex)
Output Description
Full-scale range –1 LSB
Full-scale range –2 LSB
Midscale
AO Voltage
9.999695
9.999390
0.000000
–9.999695
(Two’s Complement)
7FFF
7FFE
0000
8001
Negative full-scale range,
+1 LSB
Negative full-scale range
Any output voltage
–10.000000
—
8000
AO Voltage
------------------------------
× 32,768
10.0 V
Note If your VI does not set the output value for an AO channel, then the AO channel
voltage output will be undefined.
Connecting Analog Output Signals
The AO signals are AO <0..7> and AOGND.
AO <0..7> are the eight available AO channels. AOGND is the ground
reference signal for the AO channels.
Figure 2-10 shows how to make AO connections to the NI 7831R.
© National Instruments Corporation
2-15
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
AO0
Channel 0
+
–
Load
VOUT 0
AOGND0
x8 Channels
NI 7831R
Figure 2-10. Analog Output Connections
Digital I/O
The NI 7831R has 96 bidirectional DIO lines that you can individually
configure for either input or output. When the system powers on, the DIO
lines are high-impedance. To set another power-on state, you can configure
the NI 7831R to load a VI when the system powers on. This VI can then set
the DIO lines to any power-on state.
Connecting Digital I/O Signals
The DIO signals on the NI 7831R MIO connector are DGND and
and DIO<0..39>. The DIO<0..n> signals make up the DIO port and DGND
is the ground reference signal for the DIO port. The NI 7831R has one MIO
and two DIO connectors for a total of 96 DIO lines.
Refer to Figure B-1, NI 7831R Connector Locations, and Figure B-2,
NI 7831R I/O Connector Pin Assignments, for the connector locations and
the I/O connector pin assignments on the NI 7831R.
The DIO lines on the NI 7831R are TTL-compatible. When configured as
inputs, they can receive signals from 5 V TTL, 3.3 V LVTTL, 5 V CMOS,
signals to 5 V TTL, 3.3 V LVTTL, and 3.3 V LVCMOS devices. Because
the digital outputs provide a nominal output swing of 0 to 3.3 V
(3.3 V TTL), the DIO lines cannot drive 5 V CMOS logic levels.
NI 7831R User Manual
2-16
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
To interface to 5 V CMOS devices, you must provide an external pull-up
resistor to 5 V. This resistor pulls up the 3.3 V digital output from the
NI 7831R to 5 V CMOS logic levels. Refer to Appendix A, Specifications,
for detailed DIO specifications.
Caution Exceeding the maximum input voltage ratings, listed in Table B-2, NI 7831R I/O
Signal Summary, can damage the NI 7831R and the computer. NI is not liable for any
damage resulting from such signal connections.
Caution Do not short the DIO lines of the NI 7831R directly to power or to ground. Doing
so can damage the NI 7831R by causing excessive current to flow through the DIO lines.
provide higher current sourcing or sinking capability. If you connect
multiple digital output lines in parallel, your application must drive all of
these lines simultaneously to the same value. If you connect digital lines
together and drive them to different values, excessive current can flow
through the DIO lines and damage the NI 7831R. Refer to Appendix A,
Specifications, for more information about DIO specifications.
© National Instruments Corporation
2-17
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Figure 2-11 shows signal connections for three typical DIO applications.
LED
TTL or
LVCMOS
Compatible
Devices
+5 V
DGND
†
*
DIO<4..7>
DIO<0..3>
5 V CMOS
TTL, LVTTL, CMOS, or LVCMOS Signal
+5 V
Switch
DGND
I/O Connector
NI 7831R
*
3.3 V CMOS
†
Use a pull-up resistor when driving 5 V CMOS devices.
Figure 2-11. Example Digital I/O Connections
Figure 2-11 shows DIO<0..3> configured for digital input and DIO<4..7>
configured for digital output. Digital input applications include receiving
TTL, LVTTL, CMOS, or LVCMOS signals and sensing external device
states, such as the state of the switch shown in the figure. Digital output
applications include sending TTL or LVCMOS signals and driving external
devices, such as the LED shown in Figure 2-11.
The NI 7831R SH68-C68-S shielded cable contains 34 twisted pairs of
conductors. To maximize the digital I/O available on the NI 7831R, some
of the DIO lines are twisted with power or ground and some DIO lines are
twisted with other DIO lines. To obtain maximum signal integrity, place
edge-sensitive or high-frequency digital signals on the DIO lines that are
NI 7831R User Manual
2-18
Download from Www.Somanuals.com. All Manuals Search And Download.
ni.com
Chapter 2
Hardware Overview of the NI 7831R
other DIO lines can couple noise onto each other, use these lines for static
signals or non-edge-sensitive, low-frequency digital signals. Examples of
high-frequency or edge-sensitive signals include clock, trigger, pulse-width
modulation (PWM), encoder, and counter signals. Examples of static
signals or non-edge-sensitive, low-frequency signals include LEDs,
switches, and relays. Table 2-4 summarizes these guidelines.
Table 2-4. DIO Signal Guidelines for the NI 7831R
SH68-C68-S Shielded Cable
Signal Pairing
Recommended Types
of Digital Signals
Digital Lines
Connector 0, DIO<0..7>;
Connector 1, DIO<0..27>;
Connector 2, DIO<0..27>
DIO line paired with power
or ground
All types—high-frequency or
low-frequency signals,
edge-sensitive or
non-edge-sensitive signals
Connector 0, DIO<8..15>;
Connector 1, DIO<28..39>;
Connector 2, DIO<28..39>
DIO line paired with another
DIO line
Static signals or
non-edge-sensitive,
low-frequency signals
RTSI Trigger Bus
The NI 7831R can send and receive triggers through the RTSI trigger bus.
The RTSI bus provides eight shared triggers lines that connect to all the
devices on the bus. In PXI, the trigger lines are shared between all the PXI
slots in a bus segment. In PCI, the RTSI bus is implemented through a
ribbon cable connected to the RTSI connector on each device that needs to
access the RTSI bus.
You can use the RTSI trigger lines to synchronize the NI 7831R to any
other device that supports RTSI triggers. On the NI PCI-7831R, the RTSI
trigger lines are labeled RTSI/TRIG<0..6> and RTSI/OSC. On the
NI PXI-7831R, the RTSI trigger lines are labeled PXI/TRIG<0..7>. In
addition, the NI PXI-7831R can use the PXI star trigger line to send or
receive triggers from a device plugged into Slot 2 of the PXI chassis. The
PXI star trigger line on the NI PXI-7831R is PXI/STAR.
The NI 7831R can configure each RTSI trigger line either as an input or an
output signal. Because each trigger line on the RTSI bus is connected in
parallel to all the other RTSI devices on the bus, only one device should
drive a particular RTSI trigger line at a time. For example, if one
NI PXI-7831R is configured to send out a trigger pulse on PXI/TRIG0,
© National Instruments Corporation
2-19
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
the remaining devices on that PXI bus segment must have PXI/TRIG0
configured as an input.
Caution Do not drive the same RTSI trigger bus line with the NI 7831R and another device
simultaneously. Such signal driving can damage both devices. NI is not liable for any
damage resulting from such signal driving.
For more information on using and configuring triggers, select Help»VI,
Function, & How-To Help in LabVIEW to view the LabVIEW Help.
Refer to the PXI Hardware Specification Revision 2.1 and PXI Software
Specification Revision 2.1 at pxisa.orgfor more information about PXI
triggers.
PXI Local Bus (for NI PXI-7831R only)
The NI PXI-7831R can communicate with other PXI devices using the PXI
local bus. The PXI local bus is a daisy-chained bus that connects each PXI
peripheral slot with its adjacent peripheral slot on either side. For example,
the right local bus lines from a PXI peripheral slot connect to the left local
bus lines of the adjacent slot on the right. Each local bus is 13 lines wide.
All of these lines connect to the FPGA on the NI PXI-7831R. The PXI local
bus right lines on the NI PXI-7831R are PXI/LBR<0..12>. The PXI local
bus left lines on the NI PXI-7831R are PXI/LBLSTAR<0..12>.
The NI PXI-7831R can configure each PXI local bus line either as an input
or an output signal. Only one device can drive the same physical local bus
line at a time. For example, if the NI PXI-7831R is configured to drive a
signal on PXI/LBR 0, the device in the slot immediately to the right must
have its PXI/LBLSTAR 0 line configured as an input.
Caution Do not drive the same PXI local bus line with the NI PXI-7831R and another
device simultaneously. Such signal driving can damage both devices. NI is not liable for
any damage resulting from such signal driving.
The NI PXI-7831R local bus lines are only compatible with 3.3 V signaling
LVTTL and LVCMOS levels.
Caution Do not enable the local bus lines on an adjacent device if the device drives
anything other than 0–3.3V LVTTL signal levels on the NI PXI-7831R. Enabling the lines
enabling such lines.
NI 7831R User Manual
2-20
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
The left local bus lines from the left peripheral slot of a PXI backplane
(Slot 2) are routed to the star trigger lines of up to 13 other peripheral slots
in a two-segment PXI system. This configuration provides a dedicated,
delay-matched trigger signal between the first peripheral slot and the
other peripheral slots for precise trigger timing signals. For example, an
NI PXI-7831R in Slot 2 can send an independent trigger signal to each
device plugged into Slots <3..15> using the PXI/LBLSTAR<0..12>. Each
device receives its trigger signal on its own dedicated star trigger line.
Caution Do not configure the NI 7831R and another device to drive the same physical star
trigger line simultaneously. Such signal driving can damage the NI 7831R and the other
device. NI is not liable for any damage resulting from such signal driving.
Refer to the PXI Hardware Specification Revision 2.1 and PXI Software
PXI triggers.
Switch Settings
Refer to Figure 2-2 for the location of switch SW1 on the NI PXI-7831R
and Figure 2-3 for the location of switch SW1 on the NI PCI-7831R. For
normal operation, switch 1 is in the OFF position. To prevent a VI stored
in flash memory from loading to the FPGA at power up, move switch 1 to
the ON position, as shown in Figure 2-12.
ON
ON
1 2 3
1 2 3
a. Normal Operation (Default)
b. Prevent VI From Loading
Figure 2-12. Switch Settings on Switch SW1
Complete the following steps to prevent a VI stored in flash memory from
loading to the FPGA:
1. Power off and unplug the PXI/CompactPCI chassis or PCI computer.
2. Remove the NI 7831R from the PXI/CompactPCI chassis or PCI
computer.
3. Move switch 1 to the ON position, as shown in Figure 2-12b.
© National Instruments Corporation
2-21
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
4. Reinsert the NI 7831R into the PXI/CompactPCI chassis or PCI
computer. Refer to the Installing the Hardware section of the Getting
Started with the NI 7831R document for installation instructions.
5. Plug in and power on the PXI/CompactPCI chassis or PCI computer.
After completing this procedure, a VI stored in flash memory does not load
to the FPGA at power-on. You can use software to configure the NI 7831R
if necessary. To return to the defaults of loading from flash memory, repeat
the previous procedure but return switch 1 to the OFF position in step 3.
You can use this switch to enable/disable the ability to load from flash. In
addition to this switch, you must configure the device with the software to
autoload.
Note When the NI 7831R is powered on with switch 1 in the ON position, the analog
circuitry does not return properly calibrated data. Move the switch to the ON position only
while you are using software to reconfigure the NI 7831R for the desired power-up
behavior. Afterward, return switch 1 to the OFF position.
Power Connections
Two pins on each I/O connector supply 5 V from the computer power
supply using a self-resetting fuse. The fuse resets automatically within a
few seconds after the overcurrent condition is removed. The +5V pins are
referenced to DGND and can power external digital circuitry. The
NI 7831R has the following power rating:
+4.50 to +5.25 VDC at 1 A (250 mA max per +5V pin, 1 A max total for
all +5V lines on the device)
Caution Do not connect the +5V power pins directly to analog or digital ground or to any
other voltage source on the NI 7831R or any other device under any circumstance. Doing
so can damage the NI 7831R and the computer. NI is not liable for damage resulting from
such a connection.
NI 7831R User Manual
2-22
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 2
Hardware Overview of the NI 7831R
Field Wiring Considerations
Environmental noise can seriously affect the measurement accuracy of the
device if you do not take proper care when running signal wires between
signal sources and the device. The following recommendations mainly
apply to AI signal routing to the device. They also apply to signal routing
in general.
Take the following precautions to minimize noise pickup and maximize
measurement accuracy:
•
•
Use differential AI connections to reject common-mode noise.
Use individually shielded, twisted-pair wires to connect AI signals to
the device. With this type of wire, the signals attached to the positive
and negative inputs are twisted together and then covered with a shield.
You then connect this shield only at one point to the signal source
ground. This kind of connection is required for signals traveling
through areas with large magnetic fields or high electromagnetic
interference.
•
Route signals to the device carefully. Keep cabling away from noise
sources. The most common noise source in a PXI DAQ system is the
video monitor. Keep the monitor and the analog signals as far apart as
possible.
Use the following recommendations for all signal connections to the
NI 7831R:
•
Separate NI 7831R signal lines from high-current or high-voltage
lines. These lines can induce currents in or voltages on the NI 7831R
signal lines if they run in parallel paths at a close distance. To reduce
the magnetic coupling between lines, separate them by a reasonable
distance if they run in parallel or run the lines at right angles to each
other.
•
•
Do not run signal lines through conduits that also contain power lines.
Protect signal lines from magnetic fields caused by electric motors,
welding equipment, breakers, or transformers by running them through
special metal conduits.
Refer to the NI Developer Zone tutorial, Field Wiring and Noise
Considerations for Analog Signals, at ni.com/zonefor more information.
© National Instruments Corporation
2-23
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
3
Calibration
Calibration is the process of determining and/or adjusting the accuracy of
an instrument to minimize measurement and output voltage errors. On the
NI 7831R, onboard calibration DACs (CalDACs) correct these errors.
Because the analog circuitry handles calibration, the data read from the
AI channels or written to the AO channels in the FPGA VI is already
calibrated.
Three levels of calibration are available for the NI 7831R to ensure the
accuracy of its analog circuitry. The first level, loading calibration
constants, is the fastest, easiest, and least accurate. The intermediate level,
internal calibration, is the preferred method of assuring accuracy in your
application. The last level, external calibration, is the slowest, most
difficult, and most accurate.
Loading Calibration Constants
The NI 7831R is factory calibrated before shipment at approximately 25 °C
to the levels indicated in Appendix A, Specifications. The onboard
nonvolatile flash memory stores the calibration constants for the device.
Calibration constants are the values that were written to the CalDACs to
achieve calibration in the factory. The NI 7831R hardware reads these
constants from the flash memory and loads them into the CalDACs at
power-on. This occurs before you load a VI into the FPGA.
Internal Calibration
With internal calibration, the NI 7831R can measure and correct almost all
of its calibration-related errors without any external signal connections.
NI provides software to perform an internal calibration. This internal
calibration process, which generally takes less than two minutes, is the
preferred method of assuring accuracy in your application. Internal
calibration minimizes the effects of any offset and gain drifts, particularly
those due to changes in temperature. During the internal calibration
process, the AI and AO channels are compared to the NI 7831R onboard
voltage reference. The offset and gain errors in the analog circuitry are
calibrated out by adjusting the CalDACs to minimize these errors.
© National Instruments Corporation
3-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Chapter 3
Calibration
If you have NI-RIO installed, you can find the internal calibration utility at
Start»All Programs»National Instruments»NI-RIO»device»Calibrate
7831R Device. Device is the NI PXI-7831R or NI PCI-7831R device.
Immediately after internal calibration, the only significant residual
calibration error is gain error due to time and temperature drift of the
onboard voltage reference. You can minimize gain errors by performing an
external calibration. If you are primarily taking relative measurements, then
you can ignore a small amount of gain error and self-calibration is
sufficient.
The flash memory on the NI 7831R stores the results of an internal
calibration so the CalDACs automatically load with the newly calculated
calibration constants the next time the NI 7831R is powered on.
External Calibration
An external calibration refers to calibrating your device with a known
external reference rather than relying on the onboard reference. The
NI 7831R has an onboard calibration reference to ensure the accuracy of
self-calibration. The reference voltage is measured at the factory and stored
in the flash memory for subsequent internal calibrations. Externally
calibrate the device annually or more often if you use it at extreme
temperatures.
During the external calibration process, the onboard reference value is
re-calculated. This compensates for any time or temperature drift-related
errors in the onboard reference that might have occurred since the last
calibration. You can save the results of the external calibration process to
flash memory so that the NI 7831R loads the new calibration constants the
next time it is powered on. The device uses the newly measured onboard
reference level for subsequent internal calibrations.
To externally calibrate your device, use an external reference several times
more accurate than the device itself.
Refer to the NI 7831R Calibration Procedure for a detailed calibration
procedure for the NI 7831R, available by clicking Manual Calibration
Procedures at ni.com/calibration.
NI 7831R User Manual
3-2
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
A
Specifications
This appendix lists the specifications of the NI 7831R. These specifications
are typical at 25 °C unless otherwise noted.
Analog Input
Input Characteristics
Number of channels ............................... 8
Input modes............................................ DIFF, RSE, NRSE
(software-selectable; selection
applies to all 8 channels)
Type of ADC.......................................... Successive approximation
Resolution .............................................. 16 bits, 1 in 65,536
Conversion time ..................................... 4 µs
Maximum sampling rate ........................ 200 kS/s (per channel)
Input impedance
Powered on ..................................... 10 GΩ in parallel with 100 pF
Powered off..................................... 4 kΩ min
Overload.......................................... 4 kΩ min
Input signal range................................... 10 V
Input bias current ................................... 2 nA
Input offset current................................. 1 nA
Input coupling ........................................ DC
Maximum working voltage
(signal + common mode) ....................... Inputs should remain
within 12 V of ground
© National Instruments Corporation
A-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix A
Specifications
Overvoltage protection ........................... 42 V
Data transfers..........................................Interrupts, programmed I/O
Accuracy Information
Relative
Absolute Accuracy
Accuracy
Noise +
Quantization
(µV)
Absolute
Accuracy
at Full
Scale
( mV)
Nominal Range (V)
Positive Negative
% of Reading
24
Resolution (µV)
Temp
Drift
(%/°C)
Full
Full
Offset Single
Single
Point Averaged
Scale
Scale
Hours
1 Year
(µV)
Point Averaged
10.0
–10.0
0.0496 0.0507
2542
1779 165
0.0005
7.78
2170 217
Note: Accuracies are valid for measurements following an internal calibration. Measurement accuracies are listed for
operational temperatures within 1 °C of internal calibration temperature and 10 °C of external or factory-calibration
temperature. Temp drift applies only if ambient is greater than 10 °C of previous external calibration.
DC Transfer Characteristics
INL.......................................................... 3 LSB typ, 6 LSB max
DNL........................................................–1.0 to +2.0 LSB max
No missing codes resolution...................16 bits typ, 15 bits min
CMRR, DC to 60 Hz ..............................86 dB
Dynamic Characteristics
Bandwidth
Small signal (–3 dB)........................650 kHz
Large signal (1% THD)...................55 kHz
System noise...........................................1.8 LSBrms
(including quantization)
NI 7831R User Manual
A-2
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix A
Specifications
Settling Time
Accuracy
Step Size
20.0 V
2.0 V
16 LSB
7.5 µs
2.7 µs
1.7 µs
4 LSB
10.3 µs
4.1 µs
2.9 µs
2 LSB
40 µs
5.1 µs
3.6 µs
0.2 V
Crosstalk................................................. –80 dB, DC to 100 kHz
Analog Output
Output Characteristics
Number of channels ............................... 8 single-ended, voltage output
Resolution .............................................. 16 bits, 1 in 65,536
Update time............................................ 1.0 µs
Max update rate...................................... 1 MS/s
Type of DAC.......................................... Enhanced R-2R
Data transfers ......................................... Interrupts, programmed I/O
Accuracy Information
Absolute Accuracy
Absolute
Accuracy at
Nominal Range (V)
% of Reading
Positive Full
Scale
Negative Full
Scale
Temp Drift
(%/°C)
Full Scale
(mV)
24 Hours
1 Year
Offset (µV)
10.0
–10.0
0.0335
0.0351
2366
0.0005
5.88
Note: Accuracies are valid for analog output following an internal calibration. Analog output accuracies are listed for
operation temperatures within 1 °C of internal calibration temperature and 10 °C of external or factory calibration
temperature. Temp Drift applies only if ambient is greater than 10 °C of previous external calibration.
© National Instruments Corporation
A-3
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix A
Specifications
DC Transfer Characteristics
INL.......................................................... 0.5 LSB typ, 4.0 LSB max
DNL........................................................ 0.5 LSB typ, 1 LSB max
Monotonicity ..........................................16 bits, guaranteed
Voltage Output
Range...................................................... 10 V
Output coupling ......................................DC
Output impedance...................................1.25 Ω
Current drive........................................... 2.5 mA
Protection................................................Short-circuit to ground
Power-on state ........................................User configurable
Dynamic Characteristics
Settling time
Accuracy
Step Size
20.0 V
2.0 V
16 LSB
6.0 µs
2.2 µs
1.5 µs
4 LSB
6.2 µs
2.9 µs
2.6 µs
2 LSB
7.2 µs
3.8 µs
3.6 µs
0.2 V
Slew rate .................................................10 V/µs
Noise.......................................................150 µVrms, DC to 1 MHz
Glitch energy
at midscale transition.............................. 200 mV for 3 µs
Digital I/O
Number of channels................................96 input/output
Compatibility..........................................TTL
NI 7831R User Manual
A-4
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix A
Specifications
Digital logic levels
Level
Min
0.0 V
2.0 V
—
Max
0.8 V
5.5 V
0.4 V
Input low voltage (VIL)
Input high voltage (VIH)
Output low voltage (VOL),
where IOUT = –Imax (sink)
Output high voltage (VOH),
where IOUT = Imax (source)
2.4 V
—
Maximum output current
I
max (source)..................................... 5.0 mA
max (sink)........................................ 5.0 mA
I
Input leakage current.............................. 10 µA
Power-on state........................................ Programmable, by line
Data transfers ......................................... Interrupts, programmed I/O
Protection
Input................................................ –0.5 to 7.0 V
Output ............................................. Short-circuit (up to eight lines
may be shorted at a time)
Reconfigurable FPGA
Number of logic slices ........................... 5,120
Equivalent number of logic cells .... 11,520
Available embedded RAM..................... 81,920 bytes
Timebase ................................................ 40, 80, 120, 160, or 200 MHz
Timebase reference sources
NI PCI-7831R................................. Onboard clock only
NI PXI-7831R................................. Onboard clock, phase-locked to
PXI 10 MHz clock
Timebase accuracy
Onboard clock................................. 100 ppm, 250 ps jitter
© National Instruments Corporation
A-5
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix A
Specifications
Phase locked to PXI 10 MHz
Clock(NI PXI-7831R only) ....................Adds 350 ps jitter, 300 ps skew
Additional frequency dependent jitter
40 MHz............................................None
80 MHz............................................400 ps
120 MHz..........................................720 ps
160 MHz..........................................710 ps
200 MHz..........................................700 ps
Calibration
Recommended warm-up time.................15 minutes
Calibration interval.................................1 year
Onboard calibration reference
DC level...........................................5.000 V ( 3.5 mV)
(actual value stored
in Flash memory)
Temperature coefficient................... 5 ppm/°C max
Long-term stability.......................... 20 ppm/
1,000 h
Note Refer to Calibration Certificates at ni.com/calibrationto generate a
calibration certificate for the NI 7831R.
Bus Interface
PXI (NI PXI-7831R only) ......................Master, slave
PCI (NI PCI-7831R only).......................Master, slave
Power Requirement
+5 VDC ( 5%) .......................................450 mA (typ), 700 mA (max)
(does not include current drawn
from the +5 V line on the
I/O connectors)
(does not include current sourced
by the digital outputs. To
calculate the total current sourced
NI 7831R User Manual
A-6
Download from Www.Somanuals.com. All Manuals Search And Download.
ni.com
Appendix A
Specifications
by the digital outputs use the
following equation:
j
current sourced on channel i
∑
i = 1
Where j is the number of digital outputs being used to source current.
Power available at I/O connectors ......... +4.50 to +5.25 VDC at 1 A total,
250 mA per I/O connector pin
Physical
Dimensions (not including connectors)
NI PXI-7831R................................. 16 cm by 10 cm (6.3 in. by 3.9 in.)
NI PCI-7831R................................. 17 cm by 11 cm (6.7 in. by 4.3 in.)
I/O connectors........................................ Three 68-pin female high-density
VHDCI type
Maximum Working Voltage
Maximum working voltage refers to the signal voltage plus the
common-mode voltage.
Channel-to-earth..................................... 12 V, Installation Category I
Channel-to-channel ................................ 24 V, Installation Category I
Environmental
The NI 7831R is intended for indoor use only.
Operating Environment
Using 40 MHz timebase......................... 0 to 55 °C, tested in accordance
with IEC-60068-2-1 and
IEC-60068-2-2
Using 80 MHz timebase......................... 0 to 55 °C in all NI PXI chassis
except the following:
0 to 40 °C when installed in an
NI PXI-1000/B or NI PXI-101X
© National Instruments Corporation
A-7
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix A
Specifications
chassis, tested in accordance with
IEC-60068-2-1 and
IEC-60068-2-2
Relative humidity range..........................10 to 90%, noncondensing, tested
in accordance with
IEC-60068-2-56
Altitude ...................................................2,000 m at 25 °C ambient
temperature
Storage Environment
Ambient temperature range ....................–20 to 70 °C tested in accordance
with IEC-60068-2-1 and
IEC-60068-2-2
Relative humidity range..........................5 to 95%, noncondensing, tested
in accordance with
IEC-60068-2-56
Note Clean the device with a soft, non-metallic brush. Make sure that the device is
completely dry and free from contaminants before returning it to service.
Shock and Vibration (for NI PXI-7831R Only)
Operational Shock ..................................30 g peak, half-sine, 11 ms pulse
Tested in accordance with
IEC-60068-2-27. Test profile
developed in accordance with
MIL-PRF-28800F.
Random Vibration
Operating.........................................5 to 500 Hz, 0.3 grms
Nonoperating...................................5 to 500 Hz, 2.4 grms
Tested in accordance with
IEC-60068-2-64. Nonoperating
test profile exceeds the
requirements of
MIL-PRF-28800F, Class 3.
NI 7831R User Manual
A-8
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix A
Specifications
Safety
This product is designed to meet the requirements of the following
standards of safety for electrical equipment for measurement, control,
and laboratory use:
•
•
•
IEC 61010-1, EN 61010-1
UL 3111-1, UL 61010B-1
CAN/CSA C22.2 No. 1010.1
Note Refer to the product label, or visit ni.com/hardref.nsf, search by model number
or product line, and click the appropriate link in the Certification column for UL and other
safety certifications.
Electromagnetic Compatibility
Emissions ............................................... EN 55011 Class A at 10 m
FCC Part 15A above 1 GHz
Immunity................................................ EN 61326:1997 + A2: 2001,
Table 1
EMC/EMI............................................... CE, C-Tick, and FCC Part 15
(Class A) compliant
Note For full EMC compliance, operate this device with shielded cabling.
CE Compliance
This product meets the essential requirements of applicable European
Directives, as amended for CE marking, as follows:
Low-Voltage Directive (safety) ............. 73/23/EEC
Electromagnetic Compatibility
Directive (EMC) .................................... 89/336/EEC
Note Refer to the Declaration of Conformity (DoC) for this product for any additional
regulatory compliance information. Visit ni.com/hardref.nsf, search by model
number or product line, and click the appropriate link in the Certification column to obtain
the DoC for this product.
© National Instruments Corporation
A-9
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
B
Connecting I/O Signals
This appendix describes how to make input and output signal connections
The NI 7831R has two DIO connectors with 40 DIO lines per connector,
and one MIO connector with eight AI lines, eight AO lines, and 16 DIO
lines.
Figure B-1 shows the I/O connector locations for the NI PXI-7831R and
the NI PCI-7831R.
NI PXI-7831R
Reconfigurable I/O
Figure B-1. NI 7831R Connector Locations
© National Instruments Corporation
B-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix B
Connecting I/O Signals
Figure B-2 shows the I/O connector pin assignments for the I/O connectors
on the NI 7831R. The DIO connector pin assignment applies to
connectors <1..2> on the NI 7831R. The MIO connector pin assignment
applies to connector 0 on the NI 7831R.
34 68
34 68
DIO38
AI0–
DIO39
DIO37
DIO35
DIO33
DIO31
DIO29
DIO27
DIO26
DIO25
DIO24
DIO23
DIO22
DIO21
DIO20
DIO19
DIO18
DIO17
AI0+
DIO36 33 67
DIO34 32 66
AIGND1 33 67
AI1– 32 66
AIGND0
AI1+
31 65
30 64
31 65
30 64
DIO32
DIO30
AI2–
AI2+
AIGND3
AIGND2
AI3+
DIO28 29 63
+5V 28 62
+5V 27 61
DGND 26 60
AI3– 29 63
AI4– 28 62
AI4+
AIGND5 27 61
AI5– 26 60
AIGND4
AI5+
DGND
DGND 24 58
AI6–
AIGND7 24 58
25 59
25 59
AI6+
AIGND6
AI7+
23 57
22 56
21 55
23 57
22 56
21 55
DGND
DGND
DGND
AI7–
No Connect
AOGND0
AISENSE
AO0
DGND 20 54
19 53
AOGND1 20 54
19 53
AO1
DGND
AOGND2
AO2
DGND 18 52
DGND 17 51
AOGND3 18 52
AOGND4 17 51
AO3
DIO16
AO4
16 50
15 49
16 50
15 49
DGND
DGND
AOGND5
AOGND6
DIO15
DIO14
AO5
AO6
DGND 14 48
DGND 13 47
DGND 12 46
DGND 11 45
DGND 10 44
AOGND7 14 48
DIO14 13 47
DIO12 12 46
DIO10 11 45
DIO8 10 44
DIO13
DIO12
DIO11
DIO10
DIO9
DIO8
DIO7
DIO6
DIO5
DIO4
DIO3
DIO2
DIO1
DIO0
AO7
DIO15
DIO13
DIO11
DIO9
DIO7
DIO6
DIO5
DIO4
DIO3
DIO2
DIO1
DIO0
+5V
DGND
DGND
9
8
7
6
5
4
3
2
1
43
42
41
40
39
38
37
36
35
DGND
DGND
9
8
7
6
5
4
3
2
1
43
42
41
40
39
38
37
36
35
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
+5V
DIO Connector Pin Assignment
MIO Connector Pin Assignment
Figure B-2. NI 7831R I/O Connector Pin Assignments
To access the signals on the I/O connectors, you must connect a cable from
the I/O connector to a signal accessory. Plug the small VHDCI connector
end of the cable into the appropriate I/O connector and connect the other
end of the cable to the appropriate signal accessory.
NI 7831R User Manual
B-2
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix B
Connecting I/O Signals
.
Table B-1. I/O Connector Signal Descriptions
Signal Name
Reference
Direction
Description
+5V
DGND
Output
+5 VDC Source—These pins supply 5 V from the computer
power supply using a self-resetting 1 A fuse. No more than
250 mA should be pulled from a single pin.
AI<0..7>+
AI<0..7>–
AIGND
AIGND
AIGND
—
Input
Input
—
Positive input for Analog Input channels 0 through 7.
Negative input for Analog Input channels 0 through 7.
Analog Input Ground—These pins are the reference point for
single-ended measurements in RSE configuration and the
bias current return point for differential measurements.
All three ground references—AIGND, AOGND, and
DGND—are connected to each other on the NI 7831R.
AISENSE
AO<0..7>
AOGND
AIGND
AOGND
—
Input
Output
—
Analog Input Sense—This pin serves as the reference node
for AI <0..7> when the device is configured for NRSE mode.
Analog Output channels 0 through 7. Each channel can
source or sink up to 2.5 mA.
Analog Output Ground—The analog output voltages
are referenced to this node. All three ground
references—AIGND, AOGND, and DGND—are
connected to each other on the NI 7831R.
DGND
—
—
Digital Ground—These pins supply the reference for the
digital signals at the I/O connector and the 5 V supply.
All three ground references—AIGND, AOGND, and
DGND—are connected to each other on the NI 7831R.
DIO<0..15>
Connector 0
DGND
Input or
Output
Digital I/O signals.
DIO<0..39>
Connector <1..2>
Caution Connections that exceed any of the maximum ratings of input or output signals
on the NI 7831R can damage the NI 7831R and the computer. Maximum input ratings for
each signal are in the Protection column of Table B-2. NI is not liable for any damage
resulting from such signal connections
© National Instruments Corporation
B-3
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix B
Connecting I/O Signals
Table B-2. NI 7831R I/O Signal Summary
Signal
Type and
Direction
Impedance
Input/
Output
Protection
(Volts)
On/Off
Source
Sink
Signal Name
(mA at V)
(mA at V)
Rise Time
Bias
—
+5V
DO
AI
—
—
—
—
—
—
—
—
AI<0..7>+
10 GΩ in
parallelwith
100 pF
42/35
2 nA
AI<0..7>–
AI
10 GΩ in
parallelwith
100 pF
42/35
—
—
—
2 nA
AIGND
AO
AI
—
—
—
—
—
—
—
—
—
AISENSE
10 GΩ in
parallelwith
100 pF
42/35
2 nA
AO<0..7>
AO
1.25 Ω
Short-
circuit to
ground
2.5 at 10
2.5 at –10
10 V/µs
—
AOGND
DGND
AO
DO
—
—
—
—
—
—
—
—
—
—
—
—
—
—
DIO<0..15>
Connector 0
DIO
–0.5
to +7.0
5.0 at 2.4
5.0 at 0.4
12 ns
DIO<0..39>
Connector <1..2>
AI = Analog Input
AO = Analog Output
DIO = Digital Input/Output
DO = Digital Output
Connecting to CompactRIO Extension I/O Chassis
You can use the CompactRIO R Series Expansion chassis and CompactRIO
I/O modules with the NI 7831R. Refer to the CompactRIO R Series
Expansion System Installation Instructions for information about
connecting the chassis to the NI 7831R.
NI 7831R User Manual
B-4
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix B
Connecting I/O Signals
Connecting to 5B and SSR Signal Conditioning
NI provides cables that allow you to connect signals from the NI 7831R
directly to 5B backplanes for analog signal conditioning and SSR
backplanes for digital signal conditioning.
The NSC68-262650 cable connects the signals on the NI 7831R MIO
connector directly to 5B and SSR backplanes. This cable has a 68-pin male
VHDCI connector on one end that plugs into the NI 7831R MIO connector.
The other end of this cable provides two 26-pin female headers plus one
50-pin female header.
One of the 26-pin headers contains all the NI 7831R analog input signals.
You can plug this connector directly into a 5B backplane for analog input
signal conditioning. The NI 7831R AI<0..7> correspond to the 5B
backplane channels <0..7> in sequential order. Configure the AI channels
to use the NRSE input mode when using 5B signal conditioning.
The other 26-pin header contains all the NI 7831R analog output signals.
You can plug this connector directly into a 5B backplane for AO signal
conditioning. The NI 7831R AO<0..7> correspond to the 5B backplane
channels <0..7> in sequential order.
The 50-pin header contains the 16 DIO lines available on the NI 7831R
MIO connector. You can plug this header directly into an SSR backplane
for digital signal conditioning. DIO lines <0..15> correspond to the 5B
backplane Slots <0..15> in sequential order.
The 5B connector pinouts are compatible with eight-channel 5B08
backplanes and 16-channel 5B01 backplanes. Because the NI 7831R has
eight AI channels, you have access to the first eight channels in a
16-channel backplane. The SSR connector pinout is compatible with
eight-, 16-, 24-, and 32-channel SSR backplanes. You can connect to an
SSR backplane containing a number of channels unequal to the 16 DIO
lines available on the 50-pin header. In this case, you have access to only
the channels that exist on both the SSR backplane and the NSC68-262650
cable 50-pin header.
Figure B-3 shows the connector pinouts when using the NSC68-262650
cable.
© National Instruments Corporation
B-5
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix B
Connecting I/O Signals
NC
NC
NC
NC
NC
1
3
5
7
9
2
4
6
8
10
NC
NC
NC
NC
NC
NC
NC
NC
11 12
13 14
15 16
17 18
19 20
21 22
23 24
25 26
27 28
29 30
31 32
33 34
35 36
37 38
39 40
41 42
43 44
45 46
47 48
49 50
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DIO15
DIO14
DIO13
DIO12
DIO11
DIO10
DIO9
DIO8
DIO7
DIO6
DIO5
DIO4
DIO3
DIO2
DIO1
DIO0
+5V
AO0
AOGND0
AO1
AO2
AOGND2
AO3
AO4
AOGND4
AO5
AO6
AOGND6
AO7
1
3
5
7
9
2
4
6
8
10
NC
NC
AOGND1
NC
NC
AOGND3
NC
NC
AOGND5
NC
NC
AI0+
AIGND0
AI1+
AI2+
AIGND2
AI3+
AI4+
AIGND4
AI5+
AI6+
AIGND6
AI7+
1
3
5
7
9
2
4
6
8
10
AI0–
AI1–
AIGND1
AI2–
AI3–
AIGND3
AI4–
AI5–
AIGND5
AI6–
AI7–
11 12
13 14
15 16
17 18
19 20
21 22
23 24
25 26
11 12
13 14
15 16
17 18
19 20
21 22
23 24
25 26
AOGND7
NC
AIGND7
NC
NC
AISENSE
AO 0–7 Connector
Pin Assignment
AI 0–7 Connector
Pin Assignment
DIO 0–15 Connector
Pin Assignment
Figure B-3. Connector Pinouts when Using NSC68-262650 Cable
The NSC68-5050 cable connects the signals on the NI 7831R DIO
connectors directly to SSR backplanes for digital signal conditioning. This
cable has a 68-pin male VHDCI connector on one end that plugs into the
NI 7831R DIO connectors. The other end of this cable provides two 50-pin
female headers.
You can plug each of these 50-pin headers directly into an 8-, 16-, 24-, or
32-channel SSR backplane for digital signal conditioning. One of the
50-pin headers contains DIO<0..23> from the NI 7831R DIO connector.
These lines correspond to Slots <0..23> on an SSR backplane in sequential
order. The other 50-pin header contains DIO<24..39> from the NI 7831R
DIO connector. These lines correspond to Slots <0..15> on an SSR
backplane in sequential order. You can connect to an SSR backplane
containing a number of channels unequal to the number of lines on the
NI 7831R User Manual
B-6
Download from Www.Somanuals.com. All Manuals Search And Download.
ni.com
Appendix B
Connecting I/O Signals
NSC68-5050 cable header. In this case, you have access only to the
channels that exist on both the SSR backplane and the NSC68-5050 cable
header you are using.
Figure B-4 shows the connector pinouts when using the NSC68-5050
cable.
DIO23
DIO22
DIO21
DIO20
DIO19
DIO18
DIO17
DIO16
DIO15
DIO14
DIO13
DIO12
DIO11
DIO10
DIO9
DIO8
DIO7
DIO6
DIO5
DIO4
DIO3
DIO2
DIO1
1
3
5
7
9
2
4
6
8
10
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
1
3
5
7
9
2
4
6
8
10
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
11 12
13 14
15 16
17 18
19 20
21 22
23 24
25 26
27 28
29 30
31 32
33 34
35 36
37 38
39 40
41 42
43 44
45 46
47 48
49 50
11 12
13 14
15 16
17 18
19 20
21 22
23 24
25 26
27 28
29 30
31 32
33 34
35 36
37 38
39 40
41 42
43 44
45 46
47 48
49 50
NC
DIO39
DIO38
DIO37
DIO36
DIO35
DIO34
DIO33
DIO32
DIO31
DIO30
DIO29
DIO28
DIO27
DIO26
DIO25
DIO24
+5V
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DIO0
+5V
DIO 0–23 Connector
Pin Assignment
DIO 24–39 Connector
Pin Assignment
Figure B-4. Connector Pinouts when Using the NSC68-5050 Cable
© National Instruments Corporation
B-7
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
C
Using the SCB-68
Shielded Connector Block
This appendix describes how to connect input and output signals to the
NI 7831R with the SCB-68 shielded connector block.
The SCB-68 has 68 screw terminals for I/O signal connections. To use the
SCB-68 with the NI 7831R, you must configure the SCB-68 as a
general-purpose connector block. Refer to Figure C-1 for the
general-purpose switch configuration.
S5 S4 S3
S1
S2
Figure C-1. General-Purpose Switch Configuration for the SCB-68 Terminal Block
After configuring the SCB-68 switches, you can connect the I/O signals to
the SCB-68 screw terminals. Refer to Appendix B, Connecting I/O Signals,
for the connector pin assignments for the NI 7831R. After connecting
I/O signals to the SCB-68 screw terminals, you can connect the SCB-68 to
the NI 7831R with the SH68-C68-S shielded cable.
© National Instruments Corporation
C-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
D
Technical Support and
Professional Services
Visit the following sections of the National Instruments Web site at
ni.comfor technical support and professional services:
•
Support—Online technical support resources at ni.com/support
include the following:
–
Self-Help Resources—For immediate answers and solutions,
visit the award-winning National Instruments Web site for
software drivers and updates, a searchable KnowledgeBase,
product manuals, step-by-step troubleshooting wizards, thousands
of example programs, tutorials, application notes, instrument
drivers, and so on.
–
Free Technical Support—All registered users receive free Basic
Service, which includes access to hundreds of Application
Engineers worldwide in the NI Developer Exchange at
ni.com/exchange. National Instruments Application Engineers
make sure every question receives an answer.
•
•
•
Training and Certification—Visit ni.com/trainingfor
self-paced training, eLearning virtual classrooms, interactive CDs,
and Certification program information. You also can register for
instructor-led, hands-on courses at locations around the world.
System Integration—If you have time constraints, limited in-house
technical resources, or other project challenges, NI Alliance Program
members can help. To learn more, call your local NI office or visit
ni.com/alliance.
Declaration of Conformity (DoC)—A DoC is our claim of
compliance with the Council of the European Communities using
the manufacturer’s declaration of conformity. This system affords
the user protection for electronic compatibility (EMC) and product
safety. You can obtain the DoC for your product by visiting
ni.com/hardref.nsf.
•
Calibration Certificate—If your product supports calibration,
you can obtain the calibration certificate for your product at
ni.com/calibration.
© National Instruments Corporation
D-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Appendix D
Technical Support and Professional Services
If you searched ni.comand could not find the answers you need, contact
your local office or NI corporate headquarters. Phone numbers for our
worldwide offices are listed at the front of this manual. You also can visit
the Worldwide Offices section of ni.com/niglobalto access the branch
office Web sites, which provide up-to-date contact information, support
phone numbers, email addresses, and current events.
NI 7831R User Manual
D-2
ni.com
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
Symbol
Prefix
pico
Value
10–12
10–9
10– 6
10–3
103
p
n
nano
micro
milli
kilo
µ
m
k
M
G
mega
giga
106
109
Numbers/Symbols
°
Degrees.
>
≥
<
≤
–
Greater than.
Greater than or equal to.
Less than.
Less than or equal to.
Negative of, or minus.
Ohms.
Ω
/
Per.
%
Percent.
Plus or minus.
Positive of, or plus.
+
© National Instruments Corporation
G-1
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
Square root of.
+5V
+5 VDC source signal.
A
A
Amperes.
A/D
AC
ADC
Analog-to-digital.
Alternating current.
Analog-to-digital converter—An electronic device, often an integrated
circuit, that converts an analog voltage to a digital number.
AI
Analog input.
AI<i>
AIGND
AISENSE
AO
Analog input channel signal.
Analog input ground signal.
Analog input sense signal.
Analog output.
AO<i>
AOGND
ASIC
Analog output channel signal.
Analog output ground signal.
Application-Specific Integrated Circuit—A proprietary semiconductor
component designed and manufactured to perform a set of specific
functions.
B
bipolar
A signal range that includes both positive and negative values (for example,
–5 to +5 V).
NI 7831R User Manual
G-2
© National Instruments Corporation
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
C
C
Celsius.
CalDAC
CH
Calibration DAC.
Channel—Pin or wire lead to which you apply or from which you read the
analog or digital signal. Analog signals can be single-ended or differential.
For digital signals, you group channels to form ports. Ports usually consist
of either four or eight digital channels.
cm
Centimeter.
CMOS
CMRR
Complementary metal-oxide semiconductor.
Common-mode rejection ratio—A measure of an instrument’s ability to
reject interference from a common-mode signal, usually expressed in
decibels (dB).
common-mode voltage
CompactPCI
Any voltage present at the instrumentation amplifier inputs with respect to
amplifier ground.
Refers to the core specification defined by the PCI Industrial Computer
Manufacturer’s Group (PICMG).
D
D/A
Digital-to-analog.
DAC
Digital-to-analog converter—An electronic device, often an integrated
circuit, that converts a digital number into a corresponding analog voltage
or current.
DAQ
dB
Data acquisition—A system that uses the computer to collect, receive, and
generate electrical signals.
Decibel—The unit for expressing a logarithmic measure of the ratio of
two signal levels: dB = 20log10 V1/V2, for signals in volts.
DC
Direct current.
DGND
DIFF
Digital ground signal.
Differential mode.
© National Instruments Corporation
G-3
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
DIO
Digital input/output.
DIO<i>
DMA
Digital input/output channel signal.
Direct memory access—A method by which data can be transferred
to/from computer memory from/to a device or memory on the bus while the
processor does something else. DMA is the fastest method of transferring
data to/from computer memory.
DNL
DO
Differential nonlinearity—A measure in LSB of the worst-case deviation of
code widths from their ideal value of 1 LSB.
Digital output.
E
EEPROM
Electrically erasable programmable read-only memory—ROM that can be
erased with an electrical signal and reprogrammed.
F
FPGA
Field-Programmable Gate Array.
FPGA VI
A configuration that is downloaded to the FPGA and that determines the
functionality of the hardware.
G
glitch
An unwanted signal excursion of short duration that is usually unavoidable.
H
h
Hour.
HIL
Hz
Hardware-in-the-loop.
Hertz.
NI 7831R User Manual
G-4
© National Instruments Corporation
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
I
I/O
Input/output—The transfer of data to/from a computer system involving
communications channels, operator interface devices, and/or data
acquisition and control interfaces.
INL
Relative accuracy.
L
LabVIEW
Laboratory Virtual Instrument Engineering Workbench. LabVIEW is a
graphical programming language that uses icons instead of lines of text to
create programs.
LSB
Least significant bit.
M
m
Meter.
max
Maximum.
MIMO
min
Multiple input, multiple output.
Minimum.
MIO
Multifunction I/O.
monotonicity
A characteristic of a DAC in which the analog output always increases as
the values of the digital code input to it increase.
mux
Multiplexer—A switching device with multiple inputs that sequentially
connects each of its inputs to its output, typically at high speeds, in order to
measure several signals with a single analog input channel.
© National Instruments Corporation
G-5
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
N
noise
An undesirable electrical signal—Noise comes from external sources such
as the AC power line, motors, generators, transformers, fluorescent lights,
CRT displays, computers, electrical storms, welders, radio transmitters,
and internal sources such as semiconductors, resistors, and capacitors.
Noise corrupts signals you are trying to send or receive.
NRSE
Nonreferenced single-ended mode—All measurements are made with
respect to a common (NRSE) measurement system reference, but the
voltage at this reference can vary with respect to the measurement system
ground.
O
OUT
Output pin—A counter output pin where the counter can generate various
TTL pulse waveforms.
P
PCI
Peripheral Component Interconnect—A high-performance expansion bus
architecture originally developed by Intel to replace ISA and EISA. It is
achieving widespread acceptance as a standard for PCs and work-stations.
PCI offers a theoretical maximum transfer rate of 132 MB/s.
port
(1) A communications connection on a computer or a remote controller.
(2) A digital port, consisting of four or eight lines of digital input and/or
output.
ppm
pu
Parts per million.
Pull-up.
PWM
PXI
Pulse-width modulation.
PCI eXtensions for Instrumentation—An open specification that builds off
the CompactPCI specification by adding instrumentation-specific features.
NI 7831R User Manual
G-6
© National Instruments Corporation
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
R
RAM
Random-access memory—The generic term for the read/write memory that
is used in computers. RAM allows bits and bytes to be written to it as well
as read from. Various types of RAM are DRAM, EDO RAM, SRAM, and
VRAM.
resolution
The smallest signal increment that can be detected by a measurement
system. Resolution can be expressed in bits, in proportions, or in percent of
full scale. For example, a system has 12-bit resolution, one part in 4,096
resolution, and 0.0244% of full scale.
RIO
rms
Reconfigurable I/O.
Root mean square.
RSE
Referenced single-ended mode—All measurements are made with respect
to a common reference measurement system or a ground. Also called a
grounded measurement system.
RTSI
Real-time system integration bus—The timing and triggering bus that
connects multiple devices directly. This allows for hardware
synchronization across devices.
S
s
Seconds.
Samples.
S
S/s
Samples per second—Used to express the rate at which a DAQ board
samples an analog signal.
signal conditioning
slew rate
The manipulation of signals to prepare them for digitizing.
The voltage rate of change as a function of time. The maximum slew rate
of an amplifier is often a key specification to its performance. Slew rate
limitations are first seen as distortion at higher signal frequencies.
© National Instruments Corporation
G-7
NI 7831R User Manual
Download from Www.Somanuals.com. All Manuals Search And Download.
Glossary
T
THD
Total harmonic distortion—The ratio of the total rms signal due to
harmonic distortion to the overall rms signal, in decibel or a percentage.
thermocouple
A temperature sensor created by joining two dissimilar metals. The
junction produces a small voltage as a function of the temperature.
TTL
Transistor-transistor logic.
two’s complement
Given a number x expressed in base 2 with n digits to the left of the radix
point, the (base 2) number 2n – x.
V
V
Volts.
VDC
VHDCI
VI
Volts direct current.
Very high density cabled interconnect.
Virtual instrument—Program in LabVIEW that models the appearance and
function of a physical instrument.
VIH
VIL
Volts, input high.
Volts, input low.
VOH
VOL
Vrms
Volts, output high.
Volts, output low.
Volts, root mean square.
W
waveform
Multiple voltage readings taken at a specific sampling rate.
NI 7831R User Manual
G-8
© National Instruments Corporation
Download from Www.Somanuals.com. All Manuals Search And Download.
|