Hands-On Introduction to. LabVIEW. for Scientists and Engineers. Second Edition. John Essick. Reed College OXFORD UNIVERSITY PRESS

Transcription

1 Hands-On Introduction to LabVIEW for Scientists and Engineers Second Edition John Essick Reed College New York Oxford OXFORD UNIVERSITY PRESS

2 Contents. Preface xiii 1. THE WHILE LOOP AND WAVEFORM CHART LabVIEW Programming Environment Sine-Wave Plot using a While Loop and Waveform Chart Block Diagram Editing LabVIEW Help Window Front Panel Editing Pop-Up Menu Finishing the Program Program Execution Program Improvements Date-Type Representations Automatic Creation Feature Program Storage 48 Do It Yourself 50 Problems THE FOR LOOP AND WAVEFORM GRAPH For Loop Basics Sine-Wave Plot using a For Loop and Waveform Graph Waveform Graph Owned and Free Labels Creation of Sine Wave using a For Loop Cloning Block-Diagram Icons Auto-Indexing Feature Running the VI x-axis Calibration of the Waveform Graph Sine-Wave Plot using a While Loop and Waveform Graph Array Indicators and the Probe Watch Window 79 Do It Yourself 90 Problems 92 vii

3 Contents 3. THE MATHSCRIPT NODE AND XY GRAPH MathScript Node Basics Quick MathScript Node Example: Sine-Wave Plot Debugging with Error List Waveform Simulator using a MathScript Node and XY Graph Creating an xy Cluster Running the VI MathScript Interactive Window Adding Shape Options to Waveform Simulator The Enumerated Type Control Finishing the Block Diagram Running the VI Control and Indicator Clusters Creating an Icon using the Icon Editor Icon Design Connector Assignment 142 Do It Yourself 146 Problems DATA ACQUISITION USING DAQ ASSISTANT Data Acquisition Vis Data Acquisition Hardware Analog Input Modes Range and Resolution Sampling Frequency and the Aliasing Effect Measurement & Automation Explorer (MAX) Simple Analog Input Operation on a DC Voltage Digital Oscilloscope Analog Output DC Voltage Source Software-Timed Sine-Wave Generator Hardware-Timed Waveform Generator Placing a Custom-Made VI on a Block Diagram Completing and Executing Waveform Generator (Express) Modified Waveform Generator 201 Do It Yourself 203 Problems 204 viii

4 CONTENTS DATA FILES AND CHARACTER STRINGS ASCII Text and Binary Data Files Storing Data in a Spreadsheet-Formatted File Storing a One-Dimensional Data Array Transpose Option Storing a Two-Dimensional Data Array Controlling the Format of Stored Data The Path Constant and Platform Portability Fundamental File I/O Vis Adding Text Labels to a Spreadsheet File Blackslash Codes 237 Do It Yourself 239 Problems 243 SHIFT REGISTERS Shift Register Basics Quick Shift Register Example: Integer Sum Numerical Integration and Differentiation using Shift Registers Power Function Simulator VI Numerical Integration via the Trapezoidal Rule Trapezoidal Rule VI using Single Shift Register Convergence Property ofthe Trapezoidal Rule Numerical Differentiation using a Multiple Shift Registers Modularity and Automatic SubVI Creation 284 Do It Yourself 289 Problems 289 THE CASE STRUCTURE Case Structure Basics Quick Case Structure Example: Runtime Options using Property Nodes Numerical Integration using Case Structures Numerical Integration via Simpson's Rule Parity Determiner using a Boolean Case Structure Summation of Partial Sums using a Numeric Case Structure Trapezoidal Rule Contribution using a Boolean Case Structure Top-Level Simpson's Rule VI Comparison of the Trapezoidal Rule and Simpson's Rule 326 Do It Yourself 329 Problems 330 ix

5 Contents 8. DATA DEPENDENCY AND THE SEQUENCE STRUCTURE Data Dependency and Sequence Structure Basics Event Tinier using a Sequence Structure Event Timer using Data Dependency Highlight Execution 352 Do It Yourself 354 Problems ANALYSIS VIS: CURVE FITTING Thermistor Resistance-Temperature Data File Temperature Measurement using Thermistors The Linear Least-Squares Method Inputting Data to a VI using a Front-Panel Control Inputting Data to a VI by Reading from a Disk File Slicing Up a Multi-Dimensional Array Curve Fitting using the Linear Least-Squares Method Residual Plot 391 Do It Yourself 394 Problems ANALYSIS VIS: FAST FOURIER TRANSFORM The Fourier Transform Discrete Sampling and the Nyquist Frequency The Discrete Fourier Transform The Fast Fourier Transform Frequency Calculator VI FFT of Sinusoids Applying the FFT to Various Sinusoidal Inputs Magnitude of the Complex-Amplitude Observing Leakage Analytic Description ofleakage Description ofleakage Using the Convolution Theorem Windowing Estimating Frequency and Amplitude Aliasing 443 Do It Yourself 444 Problems 445 x

6 CONTENTS 11. DATA ACQUISITION AND GENERATION USING DAQMX Vis DAQmxVIs Simple Analog Input Operation on a DC Voltage Digital Oscilloscope Express VI Automatic Code Generation Limitation of Express Vis Improving Digital Oscilloscope using State Machine Architecture Analog Output Operations Waveform Generator 481 Do It Yourself 485 Problems PID TEMPERATURE CONTROL PROJECT Voltage-Controlled Bidirectional Current Driver for Thermoelectric Device PID Temperature Control Algorithm PID Temperature Control System CONTROL OF STAND-ALONE INSTRUMENTS Instrument Control using VISA Vis The VISA Session The IEEE Standard Common Commands Status Reporting Device-Specific Commands Specific Hardware used in this Chapter Measurement & Automation Explorer (MAX) Simple VISA-Based Query Operation Message Termination Getting and Setting Communication Properties using a Property Node Performing a Measurement over the Interface Bus Synchronization Methods Measurement VI Based on the Serial Poll Method Measurement VI Based on the Service Request Method Creating an Instrument Driver Using the Instrument Driver to Write an Application Program 565 Do It Yourself 571 Problems 572 APPENDIX I: CONSTRUCTION OF TEMPERATURE CONTROL SYSTEM 575 APPENDIX II: PROGRAM CROSS REFERENCE TABLE 583 Index 585 xi