National Instruments NI 4350 User Manual
NI 4350
User Manual
Temperature and Voltage Measurement Instruments
NI 4350 User Manual
May 1998 Edition
Part Number 321566B-01
© Copyright 1997, 1998 National Instruments Corporation. All rights reserved.
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Important Information
Warranty
The NI 4350 instruments are 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 workm anship, f or a period of 90 days fr om date of ship ment, as evid enced
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 p arts whic h are co vered by w arran ty.
National Instruments believes that the information in this manual 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 Instrum ents be liable for
any damages arising out of or related to this document or the information contained in it.
XCEPT AS SPECIFIED HEREIN
E
SPECIFICALLY DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
USTOMER’S RIGHT TO RECOVER DAMAGES CAUSED BY FAULT OR NEGLIGENCE ON THE PART OF NATIONAL
C
NSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER
I
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
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.
ATIONAL INSTRUMENTS MAKES NO WARRANTIES, EXPRESS OR IMPLIED, AND
, N
.
ATIONAL INSTRUMENTS
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. This limitation of the liability of National
Copyright
Under the copyright laws, this publ ication may not be r eproduced or tr ansmitted in any form, electron ic 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
BridgeVIEW™, CVI™, LabVIEW™, NI-DAQ™, and VirtualBench™ are trademarks of National Instruments
Corporation.
Product and company names listed are trademarks or trade names of their respective companies.
WARNING REGARDING MEDICAL AND CLINICAL USE OF NATIONAL INSTRUMENTS PRODUCTS
National Instruments products are not designed with components and testing intended to ensure a level of reliability
suitable for use in treatment and diagnosis of humans. Applications of National Instruments products involving
medical or clinical treatment can create a potential for accidental injury caused by product failure, or by errors on the
part of the user or application designer. Any use or application of National Instruments products for or involving
medical or clinical treatment must be performed by properly trained and qualified medical personnel, and al l traditional
medical safeguards, equipment, and procedures that are appropriate in the particular situation to prevent serious injury
or death should always continue to be used when National Instruments products are being used. National Instruments
products are NOT intended to be a substitute for any form of esta blishe d process, proced ure, or equipm ent used to
monitor or safeguard human health and safety in medical or clinical treatment.
About This Manual
Organization of This Manual........................................................................................ix
Conventions Used in This Manual................................................................................x
National Instruments Documentation.... ................................................................. ......xi
Customer Communication. ................................................................. ..........................xi
Chapter 1
Introduction
About the NI 4350 Instruments ....................................................................................1-1
What You Need to Get Started.....................................................................................1-2
Unpacking.....................................................................................................................1-3
Software Programming Choices...................................................................................1-4
National Instruments Application Software................................................... 1-4
VirtualBench...................................................................................................1-4
NI435X Instrument Driver and NI-DAQ .......................................................1-5
Optional Equipment....................................... .................................. .............................1-6
Contents
Chapter 2
Installation and Configuration
Software Installation.....................................................................................................2-1
Hardware Installation....................................................................................................2-1
Configuration................................................................................................................2-4
Power Considerations for the NI 4350 (USB)..............................................................2-5
Chapter 3
NI 4350 Operation
Warming up Your NI 4350 Instrument.........................................................................3-1
Choosing a Measurement Mode ...................................................................................3-1
Choosing a Range.........................................................................................................3-1
Choosing a Reading Rate..............................................................................................3-2
Knowing Your Signal Source.......................................................................................3-4
Floating Signal Source ................................................................................... 3-4
Ground-Referenced Signal Source.................................................................3-4
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Contents
Using Programmable Ground-Referencing.................................................................. 3-4
Using Programmable Open-Thermocouple Detection .................................................3-5
Measuring Temperature with Thermocouples..............................................................3-6
Connecting Your Thermocouple....................................................................3-8
Input Ranges ..................................................................................................3-8
Optimizing Measurements............................................................................. 3-8
Auto-Zero ............................. ... ........................................................3-9
Programmable Ground-Referencing........................................... ..... 3-9
Programmable Open-Thermocouple Detection............................... 3-10
AC Noise Effects.............................................................................3-10
Thermal EMF .................................................................................. 3-10
Measuring DC Voltage................................................................................................. 3-11
Connecting Your DC Voltage Signal............................................................. 3-11
Input Ranges ..................................................................................................3-11
Optimizing Measurements............................................................................. 3-12
Auto-Zero ............................. ... ........................................................3-12
Programmable Ground-Referencing........................................... ..... 3-12
Programmable Open-Thermocouple Detection............................... 3-13
Source Impedance............................................................................ 3-13
AC Noise Effects.............................................................................3-13
Thermal EMF .................................................................................. 3-13
Measuring Temperature with RTDs and Thermistors and Measuring Resistance....... 3-14
Introduction to RTDs..................................................................................... 3-14
Relationship of Resistance and Temperature in RTDs.................... 3-14
Connecting Your RTD................................................................................... 3-16
Introduction to Thermistors ........................................................................... 3-18
Resistance-Temperature Characteristic of Thermistors...................3-20
Connecting Your Thermistor .........................................................................3-20
Connecting Your Resistor.............................................................................. 3-21
Input Ranges ..................................................................................................3-23
Optimizing Measurements............................................................................. 3-23
Auto-Zero ............................. ... ........................................................3-23
Programmable Ground-Referencing........................................... ..... 3-24
Programmable Open-Thermocouple Detection............................... 3-24
Connecting to External Circuits ...................................................... 3-24
Two-Wire, Three-Wire, and Four-Wire Measurements..................3-24
Self-Heating.....................................................................................3-25
AC Noise Effects.............................................................................3-26
Thermal EMF .................................................................................. 3-26
Using the Current Source ............................................................................................. 3-26
Using Digital Inputs and Outputs................................................................................. 3-27
Connecting Your Digital Input and Output.................................................... 3-27
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Appendix A
Specifications
Appendix B
Signal Connections
Appendix C
Customer Communication
Glossary
Index
Figures
Figure 1-1. The Relationship between the Programming Environment,
NI-DAQ and Your Hardware ...............................................................1-6
Figure 3-1. Digital Filter Characteristics for 10 Hz Setting.....................................3-2
Figure 3-2. Effect of the Cold-Junction....................................................................3-7
Figure 3-3. Resistance-Temperature Curve for a 100 Ω Platinum RTD..................3-15
Figure 3-4. Two-Wire RTD Measurement...............................................................3-17
Figure 3-5. Four-Wire RTD Measurement...............................................................3-17
Figure 3-6. Three-Wire RTD Measurement with a Wheatstone Bridge
and a Current Source..............................................................................3-18
Figure 3-7. Three-Wire RTD Measurement.............................................. ...............3-18
Figure 3-8. Resistance-Temperature Curve of a Thermistor....................................3-19
Figure 3-9. Thermistor Measurement.......................................................................3-21
Figure 3-10. Multiple Transducer Connections to Analog Channels in
One Measurement Setup........................................................................3-22
Figure 3-11. Examples of DIO Applications..............................................................3-28
Contents
Tables
Table 2-1. LED Patterns for the NI 4350 (USB) States..........................................2-4
Table 3-1. Filtering and Sample Rates....................................................................3-3
Table 3-2. Using Programmable Ground-Referencing...........................................3-5
Table 3-3. Using Programmable, Open-Thermocouple Detection .........................3-6
Table 3-4. Callendar-Van Dusen Coefficients Corresponding
to Common RTDs..................................................................................3-16
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Contents
Table 3-5. Guidelines for Resistance Measurement............................................... 3-25
Table 3-6. Logic Family Thresholds*.....................................................................3-29
Table B-1. Using the NI 4350 (PCMCIA) with the CB-27 ....................................B-1
Table B-2. Using the NI 4350 (ISA and USB) with the TBX-68 ..........................B-3
NI 4350 User Manual viii
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This manual describes the electrical and mechanical aspects of the
NI4350 family of instruments and contains information concerning its
operation and programming.
Organization of This Manual
The NI 4350 User Manual is organized as follows:
• Chapter1, Introduction, describes the NI 4350 temperature and
voltage measurement instruments, lists what you need to get
started, describes the optional software and optional equipment,
and explains how to unpack your NI 4350 instrument.
• Chapter2, Installation and Configurati on, describes how to install
and configure your NI 4350 instrument.
• Chapter3, NI 4350 Operation, describes how to use your NI 4350
instrument and includes operation tips on taking measurements
with temperature sensors such as thermocouples, RTDs, and
thermistors, as well as measuring voltage and resistances.
• AppendixA, Specifications, lists the specifications of the NI 4350.
• AppendixB, Signal Connections, explains the signal correlation
between your NI 4350 and the accessories you might use with it.
• AppendixC, Customer Communication, contains forms you can
use to request help from National Instruments or to comment on our
products.
•The Glossary contains an alphabetical list and description of terms
used in this manual, including acronyms, abbreviations, defini tions
metric prefixes, mnemonics, and symbols.
•The Index alphabetically lists topics covered in this manual,
including the page where you can find the topic.
About
This
Manual
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National Instruments Corporation ix NI 4350 User Manual
About This Manual
Conventions Used in This Manual
The following conventions are used in this manual:
♦ The ♦ symbol indicates that the text following it applies only to a
specific NI 4350 instrument.
This icon to the left of bold italiciz ed text de notes a n ote, which alerts
you to important information.
!
bold Bold text denotes the names of menus, menu items, parameters, dialog
bold italic Bold italic text denotes a note, caution, or warning.
italic Italic text denotes emphasis, a cross reference, or an introduction to a
NI 4350 Refers to all instruments in the National Instruments 4350 family.
NI 4350 (ISA) Refers only to the NI 4350 for ISA bus computers. You may have
NI 4350 (PCMCIA) Refers only to the NI 4350 for computers with a Type II PCMCIA slot.
NI 4350 (USB) Refers only to the NI 4350 for computers that are USB compatible. You
DAQMeter 4350 Refers to any of the NI 4350 instruments.
This icon to the left of bold italiciz ed text de notes a ca ution, wh ich
advises you of precautions to take to avoid injury, data los s, or a
system crash.
box, dialog box buttons or options, icons, windows, Windows 95 tabs,
or LEDs.
key concept.
software that refers to this instrument as the PC-4350.
You may have software that refers to this instrument as the
DAQCard-4350.
may have software that refers to this instrument as the DAQPad-4350.
NI 4350 User Manual x
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National Instruments Documentation
The NI 4350 User Manual is one piece of the documentation set for yo ur
DAQ system. You could have any of several types of manuals
depending on the hardware and software in your s ystem. Use the
manuals you have as follows:
• Your DAQ hardware documentation—This documentation has
detailed information about the DAQ h ardware that plugs in to or is
connected to your computer. Use this documentation for hardware
installation and configuration instructions, specification
information about your DAQ hardware, and application hints.
• Software documentation—You may have both application software
and NI-DAQ software documentation. National Instruments
application software includes LabVIEW, LabWindows/CVI, and
VirtualBench. After you set up your hardware system, use either
your application software documentation or the NI-DAQ
documentation to help you write your application. If you have a
large, complicated system, it is worthwhile to look through the
software documentation before you configure your hardware.
• Accessory installation guides or manuals—If you are using
accessory products, read the terminal block, adapter, and cable
assembly installation guides. They explain how to physically
connect the relevant pieces of the system. Consult these guides
when you are making your connections.
About This Manual
Customer Communication
National Instruments wants to receive your comments on our products
and manuals. We are interested in the applications you develop with
ourproducts, and we want to help if you have problems with them.
Tomake it easy for you to contact us, this manual contains comment
and configuration forms for you to complete. These forms are in
AppendixC, Customer Communication, at the end of this manual.
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National Instruments Corporation xi NI 4350 User Manual
Chapter
Introduction
This chapter describes the NI 4350 family of temperature and voltage
measurement instruments, lists what you need to get started, explains
how to unpack your NI 4350 instrument, and describes the optional
software and optional equipment.
About the NI 4350 Instruments
Thank you for buying a National Instruments 4350 instrument. The
NI 4350 family consists of three instruments for the bus of your choice:
PCMCIA, ISA, and Universal Serial Bus (USB).
The NI 4350 instruments feature accurate thermocouple and DC voltage
measurements. You can also take temperature measurements with
resistance temperature detectors (RTDs), thermistors, and ohm
measurements using the built-in precision current source. You can use
the NI 4350 instrument with a personal computer to make the same
measurements you would with standard bench-top instrume nts such as
data loggers and DMMs.
1
The NI 4350 instruments contain a 24-bit sigma-delta an alog-to -digit al
converter (ADC) with differential analog inputs. The low leakage
construction, along with analog and digital filtering, provides excel lent
resolution, accuracy, and noise rejection. With software-programmable
ground-referencing, you can reference your floating signal without
compromising voltage measurements even if the floating signal is, in
fact, ground-referenced. With software-programmable
open-thermocouple detection, you can quickly detect a thermocouple
that may have broken before or during measurement.
You can measure up to a total resistance of 600 kΩ using the built-in
25 µA precision current source. In addition, the NI 4350 instruments
have programmable TTL-compatible digital I/O (DIO) for monitoring
TTL-level inputs, interfacing with external devices, and generating
alarms.
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Chapter 1 Introduction
The NI4350 instrument is Plug and Play compatible. The instrument is
fully software-calibrated. Because the NI4350 instrument works with a
variety of operating systems, you can develop applications that scale
across several platforms.
A system based on an NI4350 instrument offers flexibility,
performance, and size, making it ideal for service, repair, and
manufacturing and for use in industrial and laboratory environments.
The NI4350 instrument, used with your computer, is a versatile,
cost-effective platform for high-resolution measurements.
Detailed specifications for the NI4350 instruments are in AppendixA,
Specifications.
What You Need to Get Started
To set up and use your NI 4350 instrument, you wi ll need the followin g:
❑One of the following NI 4350 instruments:
– NI 4350 (PCMCIA)
– NI 4350 (ISA)
– NI 4350 (USB)
❑NI-DAQ 5.1.1 for PC compatibles or higher
❑NI435X instrument driver
❑One of the following software packages and documentation:
– VirtualBench 2.1 or higher
– LabVIEW 4.0 or higher
– LabWindows/CVI 4.0 or higher
– BridgeVIEW 1.0 or higher
– Third party compiler
❑Optional cables and accessories
❑Phillips-head screwdriver for the NI4350(ISA)
❑Your computer
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Unpacking
Chapter 1 Introduction
♦ NI 4350 (PCMCIA)
Your NI 4350 (PCMCIA) is shipped in an antistatic vinyl case; when
you are not using your NI 4350 (PCMCIA), store it in this case. Because
your NI 4350 (PCMCIA) is enclosed in a fully shielded case, no
additional electrostatic precautions are necessary. However, for your
own safety and to protect your NI 4350 (PCMC IA), never a ttempt to
touch the pins of the connectors.
♦ NI 4350 (ISA)
Your NI 4350 (ISA) is shipped in an antistatic vinyl package to prevent
electrostatic damage to your instrument. Electrostatic discharge can
damage several components on the instrument. To avoid such damage
in handling the instrument, take the following precautions:
• Ground yourself via a grounding strap or by holding a grounded
object.
• Touch the antistatic package to a metal part on your computer
chassis before removing the instrument from the package.
• Remove the instrument from the package and inspect the
instrument for loose components or any other sign of damage.
Notify National Instruments if the instrument appears damaged in
any way. Do not install a damaged instrument in your computer.
• Never touch the exposed pins of the connector.
• Also, do not touch the NI4350(ISA) printed circuit board or any
components on board. This may affect performance of the
instrument.
Caution: The NI 4350 (ISA) is ESD/contamination sensitive. Handle the board
!
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National Instruments Corporation 1-3 NI 4350 User Manual
using the edges or metal bracket.
♦ NI 4350 (USB)
Your NI 4350 (USB) is shipped in an antistatic vinyl package; when you
are not using your NI 4350 (USB), store in it this case. Because your
NI 4350 (USB) is enclosed in a fully shielded case, no additional
electrostatic precautions are necessary. However, for your own safety
and to protect your NI 4350 (USB), never attempt to touch the pins of
the connectors.
Chapter 1 Introduction
Software Programming Choices
There are several options to choose from to program and use your
National Instruments DAQ instruments. You can use LabVIEW,
LabWindows/CVI, VirtualBench, or the NI435X instrument driver.
National Instruments Application Software
LabVIEW and LabWindows/CVI are innovative program development
software packages for data acquisition and control applications.
LabVIEW uses graphical programming, whereas LabWindows/CVI
enhances traditional programming languages. Both packages include
extensive libraries for data acquisition, instrument control, data
analysis, and graphical data presentation.
LabVIEW features interactive graphics, a state-of-the-art user interface
and a powerful graphical programming language. The LabVIEW Data
Acquisition VI Library, a series of VIs for using L abVIEW with
National Instruments DAQ hardware, is included with LabVIEW. The
LabVIEW Data Acquisition VI Library is functionally equivalent to the
NI-DAQ software.
LabWindows/CVI features interactive graphics, a state-of-the-art user
interface, and uses the ANSI standard C programming language. The
LabWindows/CVI Data Acquisition Library, a series of functions for
using LabWindows/CVI with National Instruments DAQ hardware, is
included with the NI-DAQ software kit. The LabWindows/CVI Data
Acquisition library is functionally equivalent to the NI-DAQ software.
NI 4350 instruments are supported by the Easy I/O for DAQ library in
LabWindows/CVI. Use of the NI435X instrument driver
is recommended while using LabWindows/CVI.
Using LabVIEW or LabWindows/CVI software will greatly reduce the
development time for your data acquisition and control application.
VirtualBench
VirtualBench is a suite of VIs that allows you to use your data
acquisition products just as you use stand-alone instruments, but you
benefit from the processing, display and storage capabilities of PCs.
VirtualBench instruments load and save waveform data to disk in the
same format that can be used with popular spreadsheet programs and
word processors. A report generation capability complements the raw
NI 4350 User Manual 1-4
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National Instruments Corporation
data storage by adding timestamps, measurements, user name, and
comments.
Your NI 4350 works with VirtualBench-Logger and
VirtualBench-DIO. VirtualBench-Logger is a turn-key application that
allows you to make measurements as you would with a standard
bench-type data logger. VirtualBench-DIO allows you to read from or
write to the digital I/O lines.
NI435X Instrument Driver and NI-DAQ
The NI43 5X instrument driver provides flexibili ty and programmability
in a standard instrument driver format.
The instrument driver application programming interface (API) is
designed after a classical, full-featured data logger instrument driver.
The NI435 X instrument driver works with LabVIEW,
LabWindows/CVI, or conventional programming languages such as C,
C++, and Visual Basic.
Whether you are using the NI435X instrument driver,
VirtualBench-Logger, LabVIEW, or LabWindows/CVI, your
application uses the NI-DAQ driver software, as illustrated in
Figure 1-1.
Chapter 1 Introduction
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Chapter 1 Introduction
VirtualBench
(Win95/NT) (Win95/NT)
LabVIEW LabWindows/CVIC/C++
DAQ VI
Library
Figure 1-1. The Relationship between the Programming Environment,
Optional Equipment
(Win95/NT) (Win95/NT)
NI 435x Instrument
Driver API
(Win95/NT)
NI-DAQ Driver Software
PCMCIA, ISA (Win95/NT)
ISA, USB (Win95)
NI 4350
NI-DAQ and Your Hardware
Visual Basic
National Instruments offers a variety of products to use with your
NI 4350, including cables, connector blocks, terminal blocks and other
accessories, as follows:
• Cables and adapters with thermocouple miniconnectors
• Connector blocks including isothermal connector blocks
• Cables and cable accessories, shielded and ribbon
For more specific information about these products, refer to your
National Instruments catalogue or web site or call the office
nearest you.
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Installation and
Chapter
Configuration
This chapter describes how to install and configure your NI 4350
instrument.
Software Installation
Install your software before you install your NI 4350 instrument. Refer
to the appropriate release notes for specific instructions on the software
installation sequence.
If you are using LabVIEW, LabWindows/CVI, or VirtualBench, refer
to the release notes for your software. After you have installed your
software, refer to the NI-DAQ release notes and follow the instructions
given there for your operating system and your software.
If you are using programming languages such as Visual Basic, C, or
C++ with NI-DAQ, follow the NI-DAQ instructions for installing third
party compilers.
After you have installed your software, you are ready to install your
hardware. Follow the appropriate instructions for your instrument.
2
Hardware Installation
♦ NI 4350 (PCMCIA)
You can install the NI 4350 (PCMCIA) in any available Type II
PCMCIA slot in your computer. Windows 95 or higher includes the
Plug and Play services your operating system will use. Windows NT 4.0
or higher includes the drivers needed to use PCMCIA cards.
The operating system configures the NI 4350 (PCMCIA) and
automatically assigns the base address and the interrupt level. Before
installing your NI 4350 (PCMCIA), consult your computer user manual
or technical reference manual for specific instructions and warnings.
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Chapter 2 Installation and Configuration
Use the following general instructions to install your NI4350
(PCMCIA):
1. Write down your NI4350 (PCMCIA) serial number on the NI 4 350
Hardware and Software ConfigurationForm in AppendixC.
2. Turn off your computer. If your computer and operating system
support hot insertion, you can insert or remove the NI4350
(PCMCIA) at any time, whether the computer is powered on or off.
3. Remove the PCMCIA slot cover on your computer.
4. Insert the 68-pin I/O connector of the NI4350(PCMCIA) into the
PCMCIA slot until the connector is firmly seated. Notice that the
NI4350(PCMCIA) connectors are keyed so that you can insert it
in only one way.
5. Run the NI-DAQ Configuration Utility to make sure that the
NI4350(PCMCIA) is configured.
6. Configure your accessory using the NI-DAQ Configuration Uti lity.
Your NI4350(PCMCIA) is now installed.
♦ NI 4350 (ISA)
You can install the NI4350(ISA) in any available ISA, AT, or XT slot
in your computer. However, for best noise performance, leave as much
room as possible between the NI4350(ISA) and other hardware.
Before installing your NI4350(ISA), consult your computer user
manual or technical reference manual for specific instructions and
warnings. Use the following general instructions to install your
NI4350(ISA):
1. Write down your NI4350(ISA) serial number on the NI 4350
Hardware and Software ConfigurationForm in AppendixC.
2. Turn off and unplug your computer.
3. Remove the top cover or access port to the I/O channel.
4. Remove the expansion slot cover on the back panel of the
computer.
Caution: The NI4350(ISA) is ESD/contamination sensitive. Handle the board
!
using the metal bracket or edges.
5. Insert the NI4350(ISA) in a 16-bit or 8-bit ISA slot. Although it
may fit tightly, do not force the instrument into place.
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Chapter 2 Installation and Configuration
6. Screw the mounting bracket of the NI 4350 (ISA) to the back panel
rail of the computer.
7. Replace the cover.
8. Plug in and turn on your computer.
9. Run the NI-DAQ Configuration Utility to make sure that your
NI 4350 (ISA) is configured.
10. Configure your accessory using the NI-DAQ Configuration Utility.
Your NI 4350 (ISA) is now installed.
♦ NI 4350 (USB)
You can connect your NI 4350 (USB) to any available USB connector,
which supports high power, bus-powered peripheral devices. The
following are general installation instructions, but consult your PC user
manual or technical reference manual for specific instructions and
warnings:
1. Connect the USB cable from the computer port or from any other
hub to the port on the NI 4350 (USB).
2. Your computer should detect the NI 4350 (USB) immediately.
When the computer recognizes the NI 4350 (USB), the LED on the
front panel blinks or lights up, depending on the status of your
device.
If the LED comes on after the NI 4350 (USB) is connected to the host,
it is functioning properly. If the LED remains off or blinks, refer to
Table 2-1.
The LED blinks on and off for one second each for as many times as
necessary, then waits three seconds before repeating the cycle.
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Chapter 2 Installation and Configuration
Table 2-1.
LED Patterns for the NI 4350 (USB) States
LED NI 4350 (USB) State Description
On Configured state Your NI 4350 (USB) is
configured.
Off Off or in the low-power,
suspend mode
Your NI 4350 (USB) is turned
off or in the low-power,
suspend mode.
1 blink Attached state Your NI 4350 (USB) is
recognized but not configured.
2 blinks Addressed state This pattern is displayed if the
host computer detects your
NI 4350 (USB) but cannot
configure it because NI-DAQ is
not properly installed or there
are no system resources
available. Check your software
installation.
3 blinks Power supply failure This pattern is displayed if the
internal power supply shuts
down. Refer to the Power
Considerations for the
NI 4350 (USB) section for more
information.
4 blinks General error state If this pattern is displayed,
Configuration
Your NI 4350 is a completely software-configurable, Plug and Play
instrument. The Plug and Play services query the instrument and
allocate the required resources. Then the operating system enables the
instrument for operation.
NI 4350 User Manual 2-4
contact National Instruments.
©
National Instruments Corporation
Chapter 2 Installation and Configuration
Power Considerations for the NI 4350 (USB)
The NI 4350 (USB) is designed to remain powered only when the USB
cable connects it to the host PC and the PC is powered.
The NI 4350 (USB) is designed to run in a stand-alone mode, drawing
power only from the USB cable. There are circumstances when the
NI 4350 (USB) may require more power than the USB power supply
can safely deliver, so if the NI 4350 (USB) tries to draw more than the
allowed current from the USB power supply, internal protection
circuitry will turn off most of the circuitry in the NI 4350 (USB) to
protect the USB supply. This over-current condition makes the LED
blink in the power supply overload pattern described in Table 2-1.
Note: When the NI 4350 (USB) turns off, any data acquisition in progress will be
aborted and the data will be lost.
The host computer has the ability to go into a power-saving suspend
mode and, during this time, the NI 4350 (USB) can go either into a
low-power mode also or remain in a fully powered, static state. This
low-power mode is important if you are using a laptop or if power
consumption is a concern.
In the powered, static state of the NI 4350 (USB), all digital outputs will
be static at a fixed voltage.
Note: Refer to the NI-DAQ function, Set_DAQ_Device_Info, in the NI-DAQ
documentation or to the Set DAQ Device Information.vi in the LabVIEW
documentation to change the settings that determine the behavior of the
NI 4350 (USB) during the suspend state. The default setting is to remain
fully powered.
©
National Instruments Corporation 2-5 NI 4350 User Manual
Chapter
NI 4350 Operation
This chapter describes how to use your NI 4350 instrument and includ es
operation tips on taking measurements with temperature sensors such as
thermocouples, RTDs, and thermistors, as well as measuring voltages
and resistances.
Warming up Your NI 4350 Instrument
To minimize the effects of thermal drift and to ensure the specified
accuracy, allow the NI 4350 instrument to warm up for at least
10 minutes after power-up before taking measurements. To maximize
the relative accuracy of measurements, take all measurements after your
NI 4350 instrument warms up for about 30 minutes.
Choosing a Measurement Mode
Each analog input channel can be configured in two possible
measurement modes — the volts mode or the 4-wire ohms mode. Use the
volts mode for thermocouple and voltage measurements and the 4-wire
ohms mode for RTD, thermistor, and resistance measurements using the
built-in current source to provide excitation for your resistive sensors.
In the 4-wire ohms mode, the software will return the resistance value
by dividing the voltage measured by the value of the current source
stored onboard.
3
Note:
VirtualBench, the NI435X instrument driver, and the DAQ Channel
Wizard select the measurement mode auto maticall y, depending on the
sensor type you specify.
Choosing a Range
The volts mode has six bipolar input ranges: ±625 mV, ±1.25 V,
±2.5 V, ±3.75 V, ±7.5 V, and ±15 V.
©
National Instruments Corporation 3-1 NI 4350 User Manual
Chapter 3 NI 4350 Operation
The 4-wire ohms mode has six corresponding input ranges when used
with the built-in 25 µΑ current source: 25 kΩ, 50 kΩ, 100 kΩ, 150 kΩ,
300 kΩ, and 600 kΩ. Choose the smallest range for the best
measurement results.
Note: With VirtualBench, the NI435X instrument driver, or the DAQ Channel
Wizard, you can specify the range based on your sensor type in engineering
units appropriate to the sensor.
Choosing a Reading Rate
The reading rate is the rate at which your NI 4350 takes a new
measurement. This rate has a direct relationship with the digital filter
built into the ADC used in the NI 4350.
The digital filter has the characteristics shown in Figure 3-1. You can
set the frequency of the first notch of this filter to 10 Hz, 50 Hz, or
60 Hz. Setting the notch filter at one of these frequencies rejects any
noise at that frequency as well as at all its multiples.
0
–20
–40
–60
–80
–100
–120
Gain (dB)
–140
–160
–180
–200
–220
–240
0102030405060
Figure 3-1.
NI 4350 User Manual 3-2
Digital Filter Characteristics for 10 Hz Setting
Frequency (Hz)
©
National Instruments Corporation
Chapter 3 NI 4350 Operation
In single-channel measurements, the reading rate is the same as the
notch filter frequency — 10, 50, or 60 readings/s. In multiple-channel
measurements, the reading rates adjust to allow the analog and digital
filters to settle to the specified accuracy.
Note: To determine the reading rate per channel when scanning multiple
channels, divide the multiple-channel measurement reading rate by the
number of channels in the scan.
In certain applications, such as resistance measurements above 25 kΩ
or voltage measurements with more than 25 kΩ of source resistance,
you should measure the same channel for up to 1 s, then switch to
another channel to achieve the specified accuracy.
To optimize measurement accuracy and minimize the noise level,
choose the 10 Hz notch filter setting.
In practice, most of the noise encountered in measurements occurs
at harmonics (multiples) of the local power line frequency (PLF).
Table 3-1 shows which programming settings to use to reject harmonics
of particular frequencies.
Table 3-1. Filtering and Sample Rates
Harmonics of
NI435X Instrument Driver
Equivalent
LabVIEW
Notch Filter
Frequency
Setting (Hz)
10 50
50 50 fast 1
60 60 fast 1 60 60 60 9.7 2.1‡
*Number of power-line cycles used for filtering
†Power line frequency
‡For resistance ranges of 50 kΩ and higher
©
National Instruments Corporation 3-3 NI 4350 User Manual
VirtualBench-Logger
PLF† (Hz) Reading Rate PLC*
slow 5
or
60
Filter Setting
PLF†
(Hz)
6
40
400
8
400
50
60
50
Noise
Frequencies
Rejected (Hz)
10, 50, 60,
and 400
50 and 400 50 8.8 2.1‡
Single-Channel
Measurement
Reading Rate
(readings/s)
10 2.8 1.4‡
Multiple-Channel
Measurement
Reading Rate
(readings/s)
Chapter 3 NI 4350 Operation
Knowing Your Signal Source
For accurate measurements, you must determine whether your signal
source is floating or ground-referenced.
Floating Signal Source
A floating signal source is one that is not connected in any way to
the building ground system but has an isolated ground-reference
point. Examples of floating signal sources are thermocouples with
ungrounded junctions and outputs of transformers, batteries,
battery-powered devices, optical isolators, and isolation amplifiers.
Ground-Referenced Signal Source
A ground-referenced signal source is one that is connected in some way
to the building system ground and is, therefore, already connected to a
common ground point with respect to the NI 4350 instrument, assuming
that the computer is plugged into the same power system. Examples of
ground-referenced signal sources are thermocouples with grounded or
exposed junctions connected to grounded test points and outputs of
plug-in devices with nonisolated outputs, voltage across RTDs,
thermistors, or resistors you may be measuring using the built-in current
source of the NI 4350.
Using Programmable Ground-Referencing
Your NI 4350 instrument has software-programmable
ground-referencing on every channel, which you can use to
ground-reference a floating signal source. This connects CH- to ground
through a 10 MΩ resistor and provides a ground-reference for your
floating signal source. Even if your signal source is ground-r eferenced,
this resistance minimizes the effects of ground-loops, as long as the
source impedance and the lead wire resistance is less than 100 Ω. Thus,
you can take accurate measurements even if you are uncertain whether
your signal source is floating or ground-referenced.
Because you can set ground-referencing on a channel-by-channel basis,
you can have ground-referenced signal sources connected to some
channels and floating signal sources connected to other channels in the
same measurement setup. Table 3-2 summarizes the settings to use for
ground-referencing.
©
NI 4350 User Manual 3-4
National Instruments Corporation
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