Data Acquisition Basics Manual LabVIEW Data Acquisition Basics Manual January 1998 Edition Part Number 320997C-01 Internet Support E-mail: [email protected] FTP Site: ftp.natinst.com Web Address: http://www.natinst.com Bulletin Board Support BBS United States: 512 794 5422 BBS United Kingdom: 01635 551422 BBS France: 01 48 65 15 59 Fax-on-Demand Support 512 418 1111 Telephone Support (USA) Tel: 512 795 8248 Fax: 512 794 5678 International Offices Australia0398795166, Austria06624579900, Belgium027570020, Brazil011288 3336, Canada(Ontario)9057850085, Canada(Québec)5146948521, Denmark45762600, Finland0972572511, France0148142424, Germany0897413130, HongKong26453186, Israel036120092, Italy02413091, Japan0354722970, Korea025967456, Mexico55202635, Netherlands0348433466, Norway32848400, Singapore2265886, Spain916400085, Sweden087304970, Switzerland0562005151, Taiwan023771200, UnitedKingdom01635523545 National Instruments Corporate Headquarters 6504 Bridge Point Parkway Austin, Texas 78730-5039 USA Tel: 512 794 0100 © Copyright 1996, 1998 National Instruments Corporation. 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Contents About This Manual Organization of This Manual...........................................................................................xiii Conventions Used in This Manual...................................................................................xiv Related Documentation....................................................................................................xvii Customer Communication...............................................................................................xvii P I ART Before You Get Started Chapter 1 How To Use This Book Chapter 2 Installing and Configuring Your Data Acquisition Hardware LabVIEW Data Acquisition Hardware Support..............................................................2-4 Installing and Configuring Your NationalInstrumentsDevice.......................................2-6 Installing and Configuring Your DAQ Device Using NI-DAQ 5.x, 6.0...........2-6 Configuring Your DAQ Device Using NI-DAQ 4.8.x on the Macintosh.........2-6 Installing and Configuring Your SCXI Chassis................................................2-9 Hardware Configuration.....................................................................2-9 NI-DAQ 5.x, 6.0 Software Configuration...........................................2-10 NI-DAQ 4.8.x Software Configuration...............................................2-10 Configuring Your Channels in NI-DAQ 5.x, 6.0..............................................2-13 Chapter 3 Basic LabVIEW Data Acquisition Concepts Location of Common DAQ Examples.............................................................................3-1 Locating the Data Acquisition VIs in LabVIEW.............................................................3-3 DAQ VI Organization......................................................................................................3-4 Easy VIs.............................................................................................................3-4 Intermediate VIs................................................................................................3-5 Utility VIs..........................................................................................................3-5 Advanced VIs....................................................................................................3-5 VI Parameter Conventions...............................................................................................3-6 Default and Current Value Conventions..........................................................................3-7 Common DAQ VI Parameters.........................................................................................3-7 © National Instruments Corporation v LabVIEW Data Acquisition Basics Manual Contents Error Handling.................................................................................................................3-8 Channel, Port, and Counter Addressing..........................................................................3-9 Channel Name Addressing................................................................................3-10 Channel Number Addressing............................................................................3-10 Limit Settings..................................................................................................................3-12 Data Organization for Analog Applications....................................................................3-14 Chapter 4 Where You Should Go Next Questions You Should Answer.......................................................................................4-3 P II ART Catching the Wave with Analog Input Chapter 5 Things You Should Know about Analog Input Defining Your Signal......................................................................................................5-1 What Is Your Signal Referenced To?...............................................................5-2 Grounded Signal Sources...................................................................5-2 Floating Signal Sources......................................................................5-3 Choosing Your Measurement System.............................................................................5-4 Resolution.........................................................................................................5-4 Device Range....................................................................................................5-5 Signal Limit Settings.........................................................................................5-6 Considerations for Selecting Analog Input Settings.......................................................5-7 Differential Measurement System....................................................................5-9 Referenced Single-Ended Measurement System..............................................5-11 Nonreferenced Single-Ended Measurement System.........................................5-11 Channel Addressing with the AMUX-64T......................................................................5-13 The AMUX-64T Scanning Order.....................................................................5-14 Important Terms You Should Know...............................................................................5-17 Chapter 6 One-Stop Single-Point Acquisition Single-Channel, Single-Point Analog Input....................................................................6-1 Multiple-Channel Single-Point Analog Input.................................................................6-3 Using Analog Input/Output Control Loops.....................................................................6-6 Using Software-Timed Analog I/O Control Loops...........................................6-6 Using Hardware-Timed Analog I/O Control Loops.........................................6-7 Improving Control Loop Performance..............................................................6-9 LabVIEW Data Acquisition Basics Manual vi © National Instruments Corporation Contents Chapter 7 Buffering Your Way through Waveform Acquisition Can You Wait for Your Data?.........................................................................................7-1 Acquiring a Single Waveform...........................................................................7-2 Acquiring Multiple Waveforms........................................................................7-3 Simple-Buffered Analog Input Examples........................................................................7-5 Simple-Buffered Analog Input with Graphing..................................................7-5 Simple-Buffered Analog Input with Multiple Starts.........................................7-7 Simple-Buffered Analog Input with a Write to Spreadsheet File.....................7-8 Triggered Analog Input.....................................................................................7-8 Do You Need To Access Your Data during Acquisition?...............................................7-8 Continuously Acquiring Data from Multiple Channels....................................7-10 Asynchronous Continuous Acquisition Using DAQ Occurrences....................7-11 Circular-Buffered Analog Input Examples......................................................................7-12 Basic Circular-Buffered Analog Input..............................................................7-13 Other Circular-Buffered Analog Input Examples.............................................7-13 Cont Acq&Chart (buffered).vi............................................................7-14 Cont Acq&Graph (buffered).vi...........................................................7-14 Cont Acq to File (binary).vi................................................................7-14 Cont Acq to File (scaled).vi................................................................7-14 Cont Acq to Spreadsheet File.vi.........................................................7-14 Simultaneous Buffered Waveform Acquisition andWaveform Generation...................7-14 Chapter 8 Controlling Your Acquisition with Triggers Hardware Triggering........................................................................................................8-1 Digital Triggering..............................................................................................8-2 Digital Triggering Examples...............................................................8-4 Digital Triggering Examples...............................................................8-5 Analog Triggering.............................................................................................8-5 Analog Triggering Examples..............................................................8-7 Software Triggering.........................................................................................................8-8 Conditional Retrieval Examples.........................................................8-11 Chapter 9 Letting an Outside Source Control Your Acquisition Rate Externally Controlling Your Channel Clock...................................................................9-3 Externally Controlling Your Scan Clock.........................................................................9-6 Externally Controlling the Scan and Channel Clocks.....................................................9-8 © National Instruments Corporation vii LabVIEW Data Acquisition Basics Manual Contents P III ART Making Waves with Analog Output Chapter 10 Things You Should Know about Analog Output Single-Point Output.........................................................................................................10-1 Buffered Analog Output..................................................................................................10-1 Chapter 11 One-Stop Single-Point Generation Single-Immediate Updates..............................................................................................11-1 Multiple-Immediate Updates...........................................................................................11-3 Chapter 12 Buffering Your Way through Waveform Generation Buffered Analog Output..................................................................................................12-1 Changing the Waveform during Generation:Circular-BufferedOutput........................12-4 Eliminating Errors from Your Circular-BufferedApplication........................................12-6 Buffered Analog Output Examples.................................................................................12-6 Chapter 13 Letting an Outside Source Control Your Update Rate Externally Controlling Your Update Clock.....................................................................13-1 Supplying an External Test Clock from Your DAQ Device...........................................13-3 Chapter 14 Simultaneous Buffered Waveform Acquisition and Generation Using E-Series MIO Boards............................................................................................14-1 Software Triggered...........................................................................................14-2 Hardware Triggered..........................................................................................14-3 Using Legacy MIO Boards..............................................................................................14-4 Software Triggered...........................................................................................14-4 Hardware Triggered..........................................................................................14-6 Using Lab/1200 Boards...................................................................................................14-7 LabVIEW Data Acquisition Basics Manual viii © National Instruments Corporation Contents P IV ART Getting Square with Digital I/O Chapter 15 Things You Should Know about Digital I/O Types of Digital Acquisition/Generation.........................................................................15-2 Chapter 16 When You Need It Now—Immediate Digital I/O Chapter 17 Shaking Hands with a Digital Partner Sending Out Multiple Digital Values..............................................................................17-3 Non-Buffered Handshaking.............................................................................................17-5 Buffered Handshaking.....................................................................................................17-6 Simple Buffered Examples................................................................................17-7 Circular-Buffered Examples..............................................................................17-9 P V ART SCXI—Getting Your Signals in Great Condition Chapter 18 Things You Should Know about SCXI What Is Signal Conditioning?..........................................................................................18-1 Amplification...................................................................................................................18-3 Isolation...........................................................................................................................18-4 Filtering............................................................................................................................18-4 Transducer Excitation......................................................................................................18-5 Linearization....................................................................................................................18-5 Chapter 19 Hardware and Software Setup for Your SCXI System SCXI Operating Modes...................................................................................................19-4 Multiplexed Mode for Analog Input Modules..................................................19-4 Multiplexed Mode for the SCXI-1200 (Windows).............................19-4 Multiplexed Mode for Analog Output Modules................................................19-5 Multiplexed Mode for Digital and Relay Modules...........................................19-5 © National Instruments Corporation ix LabVIEW Data Acquisition Basics Manual Contents Parallel Mode for Analog Input Modules.........................................................19-5 Parallel Mode for the SCXI-1200 (Windows)....................................19-6 Parallel Mode for Digital Modules...................................................................19-6 SCXI Software Installation and Configuration...............................................................19-6 Chapter 20 Special Programming Considerations for SCXI SCXI Channel Addressing..............................................................................................20-1 SCXI Gains......................................................................................................................20-3 SCXI Settling Time...........................................................................................20-5 Chapter 21 Common SCXI Applications Analog Input Applications for MeasuringTemperatureand Pressure............................21-2 Measuring Temperature with Thermocouples..................................................21-2 Temperature Sensors for Cold-JunctionCompensation.....................21-3 Amplifier Offset.................................................................................21-5 VI Examples.......................................................................................21-6 Measuring Temperature with RTDs.................................................................21-10 Measuring Pressure with Strain Gauges...........................................................21-13 Analog Output Application Example..............................................................................21-16 Digital Input Application Example.................................................................................21-17 Digital Output Application Example...............................................................................21-19 Multi-Chassis Applications.............................................................................................21-20 Chapter 22 SCXI Calibration—Increasing Signal Measurement Precision EEPROM—Your System’s Holding Tank for CalibrationConstants............................22-1 Calibrating SCXI Modules..............................................................................................22-3 SCXI Calibration Methods for Signal Acquisition...........................................22-4 One-Point Calibration.........................................................................22-5 Two-Point Calibration........................................................................22-6 Calibrating SCXI Modules for Signal Generation............................................22-8 LabVIEW Data Acquisition Basics Manual x © National Instruments Corporation Contents P VI ART Counting Your Way to High-Precision Timing Chapter 23 Things You Should Know about Counters Knowing the Parts of Your Counter................................................................................23-2 Knowing Your Counter Chip...........................................................................................23-3 DAQ-STC..........................................................................................................23-4 Am9513.............................................................................................................23-4 8253/54..............................................................................................................23-4 Chapter 24 Generating a Square Pulse or Pulse Trains Generating a Square Pulse...............................................................................................24-1 DAQ-STC and Am9513....................................................................................24-2 8253/54..............................................................................................................24-3 Generating a Single Square Pulse....................................................................................24-4 DAQ-STC, Am9513..........................................................................................24-4 8253/54..............................................................................................................24-6 Generating a Pulse Train..................................................................................................24-9 Generating a Continuous Pulse Train................................................................24-9 DAQ-STC, Am9513...........................................................................24-10 8253/54................................................................................................24-12 Generating a Finite Pulse Train.........................................................................24-13 DAQ-STC, Am9513...........................................................................24-14 DAQ-STC...........................................................................................24-16 8253/54................................................................................................24-17 Counting Operations When All Your Counters Are Used..............................................24-20 Knowing the Accuracy of Your Counters.......................................................................24-22 8253/54................................................................................................24-22 Stopping Counter Generations.........................................................................................24-23 DAQ-STC, Am9513..........................................................................................24-23 8253/54..............................................................................................................24-23 © National Instruments Corporation xi LabVIEW Data Acquisition Basics Manual