Course contents
1.
Labview basics
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2.
Structures
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3.
SubVIs
File I/O
Analysis
Signal processing
Communication between loops
Instrument control
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7.
State machines, SubVIs, MainCluster
Modular programming + recording
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6.
arrays, clusters, charts, graphs
Additional lecture
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5.
for, while, case, ...
editing techniques
Controls&Indicators
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4.
virtual instruments, data flow, palettes
DAQ , Data collection, GPIB, Serial
Additional lecture
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Data Acquisition, Instrument control
SubVIs
• Modular programming
– group related functions and icons into lower level VI
– these subVIs can be called by higher level VIs
• subVI components
– connector
– icon
SubVI connectors
• Terminals that correspond to the VI controls and indicators
– data in from inputs, data passed to the outputs when VI finishes
executing
• Assigning terminals:
– click on the connector terminal with the wiring tool
– next click on the control/indicator you want to wire
– or you can first select the control/indicator with wiring tool and then
click the terminal
Terminal patterns
• You can modify the
terminal pattern
– or rotate and flip it
• It is advisable to select a
pattern which will cover
your future needs
– you can leave extra
unwired terminals
SubVI icon
• SubVI is represented by an icon on the block diagram
• VIs have a default icon
– use the icon editor to edit the icon
Create a subVI
• From scratch
– do the necessary wiring on block diagram or copy paste from an
existing VI
– connect the controls and indicators on the front panel to the
connector pane
• Use existing VI
– open a VI
– make the necessary connections in the connector pane
Creating subVI automatically
• Enclose area to be converted into a subVI
• Select Edit»Create SubVI from the Edit Menu
Add an existing VI on the block diagram as a subVI
• Add any VI on the block
diagram
– From Functions palette: Select a
VI...
VI Hierarchy
• View >> VI Hierarchy
• Hierarchical structure of all VIs in
memory
– dependencies between top-level VIs and
subVIs
Strings
• Sequence of characters
• Numeric data often passed as strings:
– file I/O
– instrument control
String functions
Example: Format Into String
Codes Display
• Display characters like carriage return,
tabs, white space
File I/O
• High-level File I/O
– They have it All in one VI: create or open file, read/write data, close
file
Express File I/O
• Write to Measurement File
Express File I/O
• Read From Measurement File
Write To Spreadsheet File.vi
• Write to text file
Read from Spreadsheet File.vi
• Read data from text file
Decimal symbol
• Write/Read To/From Spreadsheet File.vi uses operating
system settings for decimal symbol
– on windows7 you can change it from Region and Language settings
Disk streaming
• Keep the file open for multiple read/write operations
– no overhead from opening and closing the file
• If speed and disk space are crucial: use binary files
Advanced file functions
• File writing positions
• Move, Copy, Delete files
Datalog
• If manipulating complex records or
different data types and you will
only use LabVIEW, try datalog
• See Example Finder
• Fundamentals >> File input/output >>
Read/Write Datalog
TDMS
• Technical Data Mangement Solution
– saving well-documented measurement data
– quickly locating previously stored data
• http://zone.ni.com/devzone/cda/tut/p/id/3539
Keynotes
Communication between loops
• Design Patterns
– Producer/Consumer
– Master/Slave
• Local Variable
• Shared Variable
Producer/Consumer
Local Variables
• Local Variables allow data to be passed between parallel loops.
• A single control or indicator can be read or written to from more than one location in
the program
– Local Variables break the dataflow paradigm and should be used sparingly
Shared Variables
• Shared Variables are used to send data between VIs.
• Variable Types:
– Single Process: share the data among VIs on the local
computer.
– Network-published: communicate between VIs, remote
computers, and hardware through the Shared Variable
Engine.
• Shared Variable must exist within a project library.
• Shared Variable must be deployed to be available to other
projects and remote computers.
Textual Math in LabVIEW
• Integrate existing scripts with LabVIEW for faster
development
• Interactive, easy-to-use, hands-on learning
environment
• Develop algorithms, explore mathematical concepts,
and analyze results using a single environment
• Freedom to choose the most effective syntax, whether
graphical or textual within one VI
Supported Math Tools:
MathScript script node
Mathematica software
Maple software
MathSoft software
MATLAB® software
Xmath software
MATLAB ® is a registered trademark of The MathWorks, Inc.
Math with the MathScript Node
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Implement equations and algorithms textually
Input and Output variables created at the border
Generally compatible with popular m-file script language
Terminate statements with a semicolon to disable immediate
output
(Functions»Programming»
Structures»MathScript)
Prototype your equations in the interactive MathScript Window.
The Interactive MathScript Window
• Rapidly develop and test algorithms
•Share Scripts and
Variables with the Node
•View /Modify Variable
Output
content in 1D, 2D, and
Window
3D
Variable
Workspace
View/Modify
Variable Contents
User Commands
m-file Script
(LabVIEW»Tools»MathScript Window)
Signal Generation
• You can generate signals to test your programs
Normalized Frequency
• ranges from 0.0 to 1.0 in units cycles/samples
[cycles/se c]
• normalized frequency  signal frequency
sampling frequency
• Example:
– Sine Wave
[samples/s ec]
 [cycles/sa mples]
Waves and Patterns
• Wave VIs generate continuous signals according to normalized
frequency and number of samples
• Pattern VIs create patterns according to number of cycles
• Example: Sine Pattern
Simulate Signal Express
Signal Processing
• Express VIs
• Find Examples >> Analyzing and Processing Signal >> Basic
Spectral Measurement
Signal Processing
• Fourier transform
– frequency-domain representation of the signal
• Find Examples >> Analyzing and Processing Signal >> FFT and
Frequency Analysis >> FFT And Power Spectrum Units.vi
Signal Processing
Filters
• Find Examples >> Analyzing and
Processing Signals >> Filtering
And Conditioning >> Extract The
Sine Wave
Fitting
• Find Examples >> Analyzing
and Processing Signal >> Curve
Fitting and Interpolation >>
Parametric Curve Fitting.vi