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hands
on
Introduction to LabVIEW and Computer-Based
Measurements Hands-On Seminar
1
Company Profile
•
Leaders in Computer-Based
Measurement and Automation
•
Long-term Track Record of
Growth and Profitability
•
$660M Revenue in 2006
•
$184.4M in Q3 2007 (12% YOY)
•
More than 4,300+ employees;
operations in 40+ countries
•
Fortune’s 100 Best Companies to
Work For 8th Consecutive Year
•
FT 50 Best Workplaces UK 2006 &
2007
2
National Instruments Vision
“To do for test and measurement what the
spreadsheet did for financial analysis.”
Virtual Instrumentation
The software is the instrument
3
Hands-on Introduction to Data Acquisition with LabVIEW
1
The NI Approach – An Integrated Platform
PXI Modular Instrumentation
Multifunction High-Resolution
Data AcquisitionDigitizers and DMMs Digital I/O
High-Speed
Digitizers
Acoustics
RF
Signal
Keypad
LCD
Sound
Instrument
Control
Dynamic
Signal Acquisition
Temperature
Monitoring
Process Control
Battery
Laptop PC
Desktop PC
Counter/
Timers
Machine
Vision
Waste Monitoring
PDA
Distributed I/O and
Embedded Control
Motion
Control
Body & Chassis Audio Engine
Durability
Motor and
Valve Control
Emissions
Electronics
Safety
Tire & Brake
4
Agenda
• Introduction to LabVIEW

Exercise 1: Create a simple LabVIEW VI
• Data Acquisition with LabVIEW

Exercise 2a – 2c: Introduction to Data Acquisition with LabVIEW
• Decision making in LabVIEW

Exercise 3: Controlling program execution
• Analogue Output and Digital Control

Multiple operations with Analogue IO
5
Introduction to LabVIEW
6
Hands-on Introduction to Data Acquisition with LabVIEW
2
LabVIEW Graphical Programming
• Compiled graphical development environment
• Development time reduction of four to ten times
• Tools to acquire, analyze, and present your data
7
The LabVIEW Environment
Front Panel – User Interface
Block Diagram – Compiled Code
8
Graphical Programming – Dataflow
1
Start of
Data Flow
2
VIs execute once all
inputs are available
10
Hands-on Introduction to Data Acquisition with LabVIEW
3
Automatic Multithreading in LabVIEW
• LabVIEW automatically divides each application
into multiple execution threads
• LabVIEW introduced multithreading in 1998
11
Automatic Multithreading in LabVIEW
• LabVIEW automatically divides each application
into multiple execution threads
• LabVIEW introduced multithreading in 1998
thread
thread
thread
12
Exercise 1: Create a Simple LabVIEW VI
What you will learn:
– Working in the LabVIEW environment
Create an application that:
– Simulates data collection
– Performs RMS Calculation
– Turns on an a front panel indicator when
threshold is reached
13
Hands-on Introduction to Data Acquisition with LabVIEW
4
PC-Based Data Acquisition with
LabVIEW
14
PC-Based Data Acquisition (DAQ)
15
Measuring Analogue Input Signals
Important Factors to Consider:
• Architecture


Multiplexed
Simultaneous sampling
• Sampling rate
• Resolution
To PC
…
Analogue Input
• Signal conditioning
16
Hands-on Introduction to Data Acquisition with LabVIEW
5
Analogue Input – Architectures
Multiplexed
Channel 0
Channel 0
MUX
Channel 1
AMP
ADC
Channel 1
Interchannel delay
Simultaneous sampling
Channel 0 AMP
ADC
Channel 1 AMP
ADC
Channel 0
Channel 1
No interchannel delay
17
Analogue Input – Sampling Rates
• Undersampling may result in the misrepresentation of the
measured signal (aliasing).
• After a signal is aliased, it is impossible to reconstruct the
original signal.
• For accurate frequency representation:

Sample at least 2x the highest frequency signal being measured.
• For accurate shape representation

Sample 5–10x the highest frequency signal being measured.
18
Analogue Input – Resolution
• Number of bits analogue-to-digital converter (ADC) uses to
represent a signal
• Higher resolution – detect smaller voltage changes
16-Bit versus 3-Bit Resolution
(5 kHz Sine Wave)
10.00
111
8.75
7.50
110
6.25
101
Amplitude
5.00
(Volts)
100
3-bit
011
3.75
010
2.50
001
1.25
0
16-bit
|
0
000
|
50
|
100
Time (ms)
|
|
150
200
19
Hands-on Introduction to Data Acquisition with LabVIEW
6
Analogue Input – Signal Conditioning
High voltage signals and most sensors require signal
conditioning to properly read the signal
Sensors/Signals
Signal Conditioning
Thermocouples
Amplification, Linearisation, and
Cold-Junction Compensation, Filtering
RTDs
Current Excitation,
Linearisation, Filtering
Strain Gauges
Voltage Excitation, Bridge
Configuration, Linearisation, Filtering
Common Mode or High
Voltages
Isolation
DAQ Device
20
NI CompactDAQ
Hi-Speed USB 2.0
Built-in signal
conditioning
Synchronized I/O
Mix and match over 30
hot-swappable modules
21
C Series Modules
 Accelerometer
 Strain Gauge
 Load Cells
 Digital I/O
 Thermocouples
 4 to 20mA
 High Voltage (60V)
 RTD
22
Hands-on Introduction to Data Acquisition with LabVIEW
7
Data Acquisition with LabVIEW
NI-DAQmx driver software provides connectivity between LabVIEW
and your hardware
Configuration Based
Programmatic Interface
NI-DAQmx driver configures
• Buffering
• Signal routing
• Sample rates
• etc…
• Clocking
• Triggering
23
Exercises 2a –2c:
Introduction to Data Acquisition with LabVIEW
What you will learn:
• Taking measurements from scratch
using NI CompactDAQ and
NI LabVIEW
• Create an application that

Measures from a thermocouple

Logs data to a file
24
DAQ Solution for Your Application
Rugged and Modular Test
25
Hands-on Introduction to Data Acquisition with LabVIEW
8
Analysis in LabVIEW
26
Choose Your Analysis Approach
LabVIEW has over 600 built-in analysis functions
Express VIs
Standard VIs
Configuration
Oriented
LabVIEW MathScript
Textual Math
27
LabVIEW Analysis
Built-in functions available for
signal processing, analysis and math
• Signal synthesis
• Curve fitting and interpolation
• FFT-based frequency analysis
• Mathematics
• Probability and statistics
• Time- and frequency-domain analysis
• Digital signal processing
• Waveform alignment and resampling
• Much more…
28
Hands-on Introduction to Data Acquisition with LabVIEW
9
LabVIEW Toolkits
Productivity enhancing functionality found in several toolkits,
including…
•
•
•
•
•
•
Sound & Vibration
RF and Communications
Digital Filter Design
Database Connectivity
Reporting Interface to MS Office
And many more…
29
Presenting Data in LabVIEW
30
Presenting Data
Types of controls and indicators available:
• Graphs and strip charts
• Buttons and checkboxes
• Knobs and sliders
• Text and combo boxes
• Tree controls
• Tables
• ActiveX objects
• etc...
31
Hands-on Introduction to Data Acquisition with LabVIEW
10
Options for Professional UIs
Displaying data, visualising processes and controlling machines
LabVIEW is optimised for creating technical user interfaces
32
LabVIEW File I/O
Functions for saving your data to files and databases
• ASCII
• Excel
• Binary
• Databases
NI TDM file format provides
an easy way to make test
data searchable
ni.com/tdm
33
LabVIEW Report Generation
Functions for creating reports and documenting test results
• HTML
• MS Office
• XML
• DIAdem
The Report Generation toolkit
provides connectivity to
MS Office
ni.com/diadem
NI DIAdem provides a
WYSIWYG report editor
34
Hands-on Introduction to Data Acquisition with LabVIEW
11
Controlling Program Execution
Start
Is Limit
Met?
No
Yes
Turn On
Output
Reset
Output
•
•
•
•
•
•
•
Looping (For and While)
Case structure
Sequence structure
State machines
Event structure
State diagram editor
Timed loop
35
LabVIEW Looping Basics
While Loop
For Loop
Run until stop
condition met
Run N times
36
LabVIEW Case Structure
Primary decision making block
37
Hands-on Introduction to Data Acquisition with LabVIEW
12
Exercise 3: Controlling Program Execution
What you will learn:
– How to incorporate logic into your
LabVIEW application
Create an application that:
– Charts a sine or triangle wave
depending on toggle switch position
– Turns on/off digital outputs based on
user selections
38
Analogue Output – Considerations
• Accuracy: digital-to-analog converter (DAC) resolution
• Update Rate: settling time and waveform frequency
• Range: fixed or adjustable output voltage/current
Channel 0
DAC
Channel 1
DAC
Channel 0
Channel 1
• 16-bit
• 100 kS/sec
• ±10 VDC, 0–20 mA
39
Exercise 4:
Multiple Operations with Analogue I/O
What You Will Learn
• Creating parallel operation in LabVIEW
• Create an application that

Outputs an analogue signal

Uses analogue input channel to acquire
and display on front panel
Time: 20 minutes
40
Hands-on Introduction to Data Acquisition with LabVIEW
13
Analogue Output Functions – PID Control
Analogue IO can be used in combination for control applications
Read
1 Sensor
Calculate
2 PID value
Output to
3 Actuator
41
Additional Measurement Platforms
42
NI LabVIEW™ Everywhere
Platforms:
•
•
•
•
Microprocessors
Desktop
Mobile
Industrial
Embedded
FPGA
Handheld
Wireless
Networked I/O
PC Boards
PXI
Tektronix open Windows
oscilloscopes
PC
43
Hands-on Introduction to Data Acquisition with LabVIEW
14
Modular Instrumentation
Modular Instruments
Data Acquisition



Sensors, voltage and current
I/O
Measurements: DC to 10 MHz
Resolution: ~18 to 24 bits
– DMMs, Switches, Oscilloscopes,
High-speed digital, Power
supplies, RF
– Measurements: DC to 6 GHz
– Resolution: Up to 26 bits
44
Interfacing with Benchtop Instruments
• Benchtop instruments involve:
– Fixed functionality
– Vendor defined interface
Processor
Display
RAM
Power
Supply
ROM
Hard Disk
LabVIEW uses drivers for PC connectivity
45
Instrument Control with LabVIEW
Over 5,000 Instrument drivers online, from over 250 vendors
GPIB - USB - Ethernet
RS 232 - RS 485 - LXI
ni.com/idnet
46
Hands-on Introduction to Data Acquisition with LabVIEW
15
Using NI CompactDAQ to Crash Test Safety
Helmets
Application: Designing a highly accurate and portable
high-level impact test application for the certification of
safety helmets.
NI Products Used: NI CompactDAQ
Solution: CompactDAQ is used to control the height from which the helmet under test is
dropped, as well as acquiring data related to what a person's head would be subjected to
upon impact. The system was chosen as it had sufficient throughput to ensure that each
helmet test is thoroughly and accurately documented.
“A system upgrade such as the one we required is a major budget
consideration, and for this reason we were very deliberate in our
search for a new hardware package”
47
Microsoft Uses NI LabVIEW and PXI Modular
Instruments to Develop Production Test System for
Xbox 360 Controllers
Application: Creating an updated versatile test system
to test and validate new Xbox 360 controllers.
NI Products Used: LabVIEW, Modular Instruments
and PXI/CompactPCI
Reasons for Choosing NI Products: “Using the LabVIEW graphical development
environment, we created more than 100 tests, implemented Ethernet communication, and
incorporated a data storage interface to our Microsoft SQL Server database…we
implemented a test strategy that resulted in a 50 percent increase in our test throughput per
test station.”
Microsoft Uses NI LabVIEW and PXI Modular Instruments to Develop Production Test System for Xbox 360 Controllers
NI Customer Solutions
48
Your Next Steps
• Visit ni.com/labview




Try LabVIEW Online for FREE
Read technical white papers
View webcasts on-demand
Find other seminars in your area
• Schedule a visit with your local field engineer to discuss your
application
49
Hands-on Introduction to Data Acquisition with LabVIEW
16
Useful Resources
Measurement Fundamentals
www.ni.com/measurementfundamentals
50
LabVIEW Skill Development Plan
New User
Experienced User
Advanced User
Courses
LabVIEW Advanced I
LabVIEW
Intermediate I
Core Courses
Begin
Here
LabVIEW
Basics I
LabVIEW
Basics II
Certifications
Certified LabVIEW
Associate Developer Exam
LabVIEW
Intermediate II
Certified LabVIEW
Architect Exam
Certified LabVIEW
Developer Exam
• Save development time and cost
• Differentiate skills with professional credentials
• Multiple training formats – Classroom, Onsite, Online, Self-Paced
ni.com/training
51
Questions or Comments?
ni.com/labview
52
Hands-on Introduction to Data Acquisition with LabVIEW
17
Exercise 1: Create a Simple LabVIEW VI
In this exercise, you will create a simple LabVIEW VI that simulates an analog signal and plots it
on a waveform graph. The VI will test the input values against a user-specified limit and light an
LED if the input value exceeds that limit.
Below are pictures identifying each of the palettes found in LabVIEW to assist you as you
complete these exercises.
Note: LabVIEW has a built-in Automatic Tool Selection feature that changes the behavior of the
cursor depending on what type of object you are currently pointing to.
Functions Palette
Controls Palette
1. If you have not already done so, click the LabVIEW icon on your quick launch toolbar.
Hands-on Introduction to Data Acquisition with LabVIEW
18
Once you launch LabVIEW, a splash screen like the following appears.
2. Click More…
3. Expand From Template. Notice the different categories on the left of the window that
correspond to the types of tasks from which you can choose. You can select Blank VI to
start from scratch. There are also Template VIs to use as a starting point for building your
application. Projects and Other Files are more advanced components and will not be
described in detail. To get more information on any of the listings in the New Dialog Box,
click the Help button in the lower right corner of the window.
Hands-on Introduction to Data Acquisition with LabVIEW
19
4. Select VI»From Template»Tutorial (Getting Started) »Generate and Display and click OK.
Two windows appear. The gray window is the front panel, and the white one is the block
diagram. The front panel contains the parts of your VI used for presenting information,
whereas the block diagram contains the code that controls the functionality of the VI. You
can toggle between the two windows by selecting Window»Show Block Diagram or
Window»Show Front Panel. You can also switch between the windows by pressing <Ctrl-E>
on the keyboard.
5. Examine the front panel and block diagram of this template VI. The front panel contains a
Waveform Chart and a STOP button as shown in the following figure.
Hands-on Introduction to Data Acquisition with LabVIEW
20
The block diagram contains a Simulate Signal VI, which is currently configured to simulate a
sine wave and plot it to the chart.
6. Switch back to the front panel by pressing <Ctrl-E>. Since the Run button (the white arrow
in the top left corner) is solid, you can run this VI as it is. Click the Run button and examine
the operation of the VI. When you are finished, click the STOP button on the front panel to
stop running the VI.
Note: As you will see later in the exercise, when the Run button in the upper left corner of
both the front panel and the block diagram changes from a solid white arrow, to a broken
gray arrow, this new icon indicates that the VI is currently not executable.
7. Now we can add some functionality to this basic VI. We will modify the VI to flash an alarm
whenever the signal value is above a certain level. Open the Controls palette (if it is not
open already) by right-clicking the front panel window. A small pushpin icon in the upper
left corner of this palette appears. Click this pushpin to force the palette to remain on your
screen.
Hands-on Introduction to Data Acquisition with LabVIEW
21
8. Click the Numeric Controls palette, and select a Vertical Pointer Slide to be placed on the
front panel. To do this, click the Vertical Pointer Slide and drag it to the front panel. Click
once to place it.
9. Click the Express menu item on the Controls palette to return to the Express Controls
palette.
10. Click the LEDs subpalette, and place a Round LED on the front panel.
Hands-on Introduction to Data Acquisition with LabVIEW
22
11. Right-click the Vertical Pointer Slide and select Properties. A property page will appear.
Examine the different properties that you can modify. Make the following changes on the
Appearance tab and click OK to apply the changes.
Label: Limit
Slider 1: Check Show digital display(s)
Hands-on Introduction to Data Acquisition with LabVIEW
23
12. Right-click the Round LED labeled Boolean, and select Properties. Examine the different
properties that can be modified. On the Appearance tab, change the label from Boolean to
Alarm. Click OK to apply your change. Move the objects on the front panel so it resembles
the following.
13. Switch to the block diagram by pressing <Ctrl-E>. Double-click the Simulate Signal Express
VI to bring up its properties window. Examine the different properties you can modify.
Change the Amplitude of the signal to 10. Click OK to apply this change and to close the
properties window.
Hands-on Introduction to Data Acquisition with LabVIEW
24
14. Bring up the Functions palette by right-clicking the block diagram. Select Express & Signal
Analysis and place the Amp & Level Express VI on the diagram.
15. When you place the Comparison Express VI on the block diagram, a dialog box appears.
Select RMS as shown below.
16. As shown below, wire the output of the Simulate Signal VI to Signals input on the
Amplitude and Level Measurements VI. Then right-click on RMS output and select
Create»Numeric Indicator from the context menu.
Hands-on Introduction to Data Acquisition with LabVIEW
25
17. Bring up the functions palette by right-clicking the block diagram. Select Arithmetic &
Comparison»Comparison and place the Comparison Express VI on the diagram
Hands-on Introduction to Data Acquisition with LabVIEW
26
When you place the Comparison Express VI on the block diagram, a dialog box appears that
lets you configure what type of comparison you will be doing. Make the following
selections, then click OK to apply these changes and to close the dialog box.
Compare Condition: Greater
Comparison Inputs: Compare to second input
18. You can connect Controls, Functions, and Indicators on the block diagram by pointing to an
object and clicking it when the cursor changes to a spool of wire. You can then move the
cursor to the object you want to connect it to and click again. Connect the Limit control to
the Alarm indicator.
Note: The Run button in the upper left corner of both the front panel and the block diagram
has changed from a solid white arrow, to a broken gray arrow. This new icon indicates that
Hands-on Introduction to Data Acquisition with LabVIEW
27
the VI is currently not executable. If you click the Run button when it is solid and white, it
runs the VI. Clicking it when it is broken and gray brings up a dialog box that will help you
debug the VI.
19. Click the Run button now. The resulting dialog box shows that, in this case, the error results
from connecting terminals of two different types. Since the Limit control is a Numeric type
and the Alarm indicator is a Boolean type, we cannot wire these two terminals together.
Highlight the error by clicking it, and then click Show Error. LabVIEW will highlight the
location of the error.
20. Notice that the wire between Limit and Alarm is dashed and a red  is displayed on it.
To delete this broken wire, press <Ctrl-B>. This keyboard shortcut removes all broken wires
from the block diagram.
21. Make your block diagram resemble the following image by completing the following steps.
a. Wire the Limit control to the Operand 2 input of the Comparison function.
b. Connect the wire between the Simulate Signals block and the Waveform Graph to the
Operand 1 input of the Comparison block.
c. Wire the Result output of the Comparison block to the Alarm indicator.
Your block diagram should now resemble the following:
Hands-on Introduction to Data Acquisition with LabVIEW
28
22. Switch to the front panel by pressing <Ctrl-E>.
23. Save the VI in the Desktop\CustomerWork folder by using the File menu and name it
Exercise1.vi.
Note: Be sure to save this VI, as you will be using it later in the seminar.
24. Run the VI. While running the VI, you can change the Limit value. Also notice that when a
data point received from the Simulate Signal VI is greater than the Limit value, the Alarm
indicator lights up.
While the VI is still running, switch to the block diagram by pressing <Ctrl-E>. Enable
highlight execution by clicking the light bulb on the tool bar. This will allow you to see the
flow of data through your program.
25. When you are finished, stop the VI by clicking the STOP button on the front panel.
Hands-on Introduction to Data Acquisition with LabVIEW
29
Optional Exercise 1: The LabVIEW Help System
The LabVIEW help system is a great place to learn about LabVIEW and to go when you have
questions. This exercise will introduce you to the rich source of information that is available for
you to take advantage of.
1. Go back to the VI you just created, and press <F1> on the keyboard to start the help system
2. Expand Fundamentals»LabVIEW Environment and explore the information available here,
click around and get a feel for how it is organized.
3. Take a few minutes to explore other topics in the help system.
4. Click on the Search tab try searching on analysis functions for features you might need in
your work applications.
Hands-on Introduction to Data Acquisition with LabVIEW
30
Optional Exercise 2: LabVIEW Example Finder
As you learned in Optional Exercise 1, LabVIEW has a comprehensive help system. LabVIEW also
includes an extensive set of examples that in many cases are the building blocks for your
applications. This exercise will introduce you to what examples are available.
1. Go back to the VI you created, and from the Help menu select Find Examples.
2. Expand New Examples for LabVIEW 8.5»Express and double-click on Select Signals.vi.
3. Run the VI and explore the block diagram.
4. Take a few minutes to look around at the other example programs available, search on
terms that you are familiar with, i.e., “analysis”, and try out as many as there is time for.
End of Exercise 1
Hands-on Introduction to Data Acquisition with LabVIEW
31
Exercise 2a: Data Acquisition with NI LabVIEW
Exercise Overview
Objective
Learn about data acquisition in LabVIEW
Goals
When you have completed this exercise, you will:
 Know how to configure a data acquisition device
 Know how to use the DAQ Assistant and take measurements with NI LabVIEW
Exercise Instructions
Set up hardware
1. Make sure that the NI CompactDAQ chassis (cDAQ-9172) is powered on.
2. Connect the chassis to the PC using the USB cable.
3. NI-DAQmx driver installed on the PC automatically detects the chassis and brings up the
following window.
Hands-on Introduction to Data Acquisition with LabVIEW
32
4. Click on Configure and Test This Device to open Measurement & Automation Explorer (MAX).
Note: NI Measurement & Automation Explorer is a configuration utility for all National Instruments
hardware.
Configure Hardware
5. Devices and Interfaces section under My System shows all the National Instruments
devices installed and configured on your PC. The NI-DAQmx Devices folder shows all the NIDAQmx compatible devices. By default, the NI CompactDAQ chassis NI cDAQ-9172 shows up
with the name “cDAQ1”.
6. This section of MAX also shows the installed modules as well as empty slots in the
CompactDAQ chassis.
7. Right-click on NI cDAQ-9172 and click on Self-Test.
8. The device passes the self test, which means it is configured properly and ready to be used
in your LabVIEW application.
LabVIEW
9. Open NI LabVIEW 8.5 and press <Ctrl-N> to open a blank VI.
10. Press <Ctrl-T> to tile front panel and block diagram windows.
11. Pull up the Functions Palette by right-clicking on the white space on the LabVIEW block
diagram window.
12. Move your mouse over the Express»Input palette, and click the DAQ Assist Express VI. Click
again on the white space of the LabVIEW block diagram to place the DAQ Assistant VI.
Hands-on Introduction to Data Acquisition with LabVIEW
33
13. The Create New Express Task… window appears:
14. To configure a temperature measurement application with a thermocouple, click on Analog
Input»Temperature»Thermocouple. Click the + sign next to the cDAQ1Mod1 (NI 9211),
highlight channel ai0, and click Finish. This adds a physical channel to your measurement
task.
15. Change the CJC source to Built In and Acquisition Mode to Continuous. Click the Run
button. You will see the temperature readings from the thermocouple in test panel window.
Hands-on Introduction to Data Acquisition with LabVIEW
34
16. Click OK to close the Express block configuration window to return to the LabVIEW block
diagram.
17. Notice that LabVIEW automatically creates the code for you for this measurement task.
Click Yes to automatically create a While Loop.
18. Right-click the data terminal output of the DAQ Assistant Express VI (the blue output arrow
on the right side) and select Create»Graph Indicator.
19. Notice that a graph indicator is placed on the front panel.
20. Your block diagram should now look like the figure below. The while loop automatically
adds a stop button to your front panel that allows you to stop the execution of the loop.
Hands-on Introduction to Data Acquisition with LabVIEW
35
21. Rather than displaying our data in a graph indicator, we want to display our temperature
readings in a thermometer indicator. To do this, go to the front panel by pressing <Ctrl-E>.
Right-click the graph indicator and select Replace. The Controls palette will appear. Select
Modern»Numeric»Thermometer. The thermometer indicator should now appear instead
of the graph indicator.
22. Also, right-click on the stop (F) button and select Replace. The Controls palette will appear.
Select Boolean»Stop Button.
Hands-on Introduction to Data Acquisition with LabVIEW
36
23. Modify the thermometer indicator by right-clicking it and selecting Properties. On the
Appearance Tab, change the Label to Temperature.
On the Scale tab, change the Minimum to 20 and the Maximum to 30.
Click OK when you are finished.
Hands-on Introduction to Data Acquisition with LabVIEW
37
24. Switch to the block diagram. Expand the While Loop. Your block diagram should now
resemble the following illustration.
25. To perform analysis on your data, select the Express»Signal Analysis»Statistics Express VI
and place it on your block diagram.
26. A properties window will appear. Make the following selections and click OK.
Statistical Calculations: Arithmetic Mean
Hands-on Introduction to Data Acquisition with LabVIEW
38
Extreme Values: Maximum, Minimum
27. Connect the data output of the DAQ Assistant VI to the Signals input of the Statistics VI.
Hands-on Introduction to Data Acquisition with LabVIEW
39
28. Right-click the Arithmetic Mean output of the Statistics VI and select Create»Numeric
Indicator. This will create a numeric indicator on the front panel that will display the mean.
Repeat this step for both the Maximum and Minimum outputs of the Statistics VI. Your
block diagram should resemble the following.
29. Switch to the front panel and rearrange your controls and indicators to resemble the
following.
30. Save the VI in the Desktop\CustomerWork folder by using the File menu and name it
Exercise2.vi.
Hands-on Introduction to Data Acquisition with LabVIEW
40
31. Run the VI. Hold the thermocouple between your fingers to raise the temperature. Notice
the change in temperature on the thermometer. If you are not seeing enough of a
temperature fluctuation, stop the VI and decrease the range on your thermometer
indicator.
32. Click the STOP button on the front panel when you are finished.
33. Close the VI.
End of Exercise 2a
Hands-on Introduction to Data Acquisition with LabVIEW
41
Exercise 2b: File I/O in LabVIEW
Exercise Overview
Objective
How to log data to a file using LabVIEW.
Goals
When you have completed this exercise, you will:
 Know how to use Write to Measurement File express VI and how to log data to a file using
LabVIEW.
Exercise Instructions
1. Open the VI from exercise 2a.
2. Right-click on the block diagram and select Express» Output» Write to Measurement File
and place it inside the While Loop on the block diagram.
Hands-on Introduction to Data Acquisition with LabVIEW
42
3. A configuration window will appear. Enter the following parameters and click OK.
4. Wire the output of the DAQ Assistant Express VI to the input of the Write to Measurement
File Express VI.
5. Your block diagram should now resemble the following figure .
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6. Save the VI in the Desktop\CustomerWork folder by using the File menu and name it
Exercise2b.vi.
7. Run the VI momentarily and press STOP to stop the VI.
8. Your file will be created in the folder specified.
9. Open the file using Microsoft Office Excel or Notepad. Review the header and temperature
data saved in the file.
10. Close the data file and the LabVIEW VI.
End of Exercise 2b
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Exercise 2c (Optional): Automatic Code
Generation in LabVIEW
Exercise Overview
Objective
Create DAQmx code from the DAQ Assistant.
Goals
When you have completed this exercise, you will:
 Know how to generate code automatically from the DAQ Assistant.
 Have experience using some of the NI-DAQmx VIs.
Exercise Instructions
1. Open the VI from Exercise 2a.
2. Delete all the functions and terminals from the block diagram except the DAQ Assistant.
Delete all the wires as well.
3. Right-click on the DAQ Assistant and select Generate NI-DAQmx Code.
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4. NI-DAQmx will now generate LabVIEW code using the NI-DAQmx API. Your block diagram
should now resemble this:
5. Double-click on the configuration VI (shown below) that NI-DAQmx generated for you on
your block diagram
6. The block diagram of the configuration VI should appear as shown below. This is an example
of how you can use the DAQmx VIs if you need to create customized DAQ code that includes
features beyond those offered by the DAQ Assistant.
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In this block diagram, you will see 3 SubVIs:
DAQmx Create Task.vi
DAQmx Create Channel.vi
DAQmx Timing.vi
To learn about each VI, hover your mouse over each one and press <Ctrl-H>. This will bring
up the Context Help which explains the parameters and functionalities of each VI.
7. Close the VI and do not save any changes.
End of Exercise 2c
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Exercise 3: Controlling Program Execution
If you are up for challenge, try to build the following LabVIEW application without using the
instructions; if you feel you need more guidance skip down to the section step-by-step for a
complete set of instructions.
Challenge Application
Using a While Loop, case structure, toggle switch and the Simulate Signal VI, create a simple
application that charts a sine or triangle wave depending on toggle switch position.
When you are done, save your VI as Exercise3-Decisions.vi. You will use it in the next
exercise.
If you are really up for a challenge add logic to the VI so it will stop either when you press the
stop button or when the loop iterations have exceeded 10,000.
Step By Step Instructions
In this exercise, you will create a LabVIEW VI that will output a triangle or sine wave to a front
panel graph depending on the state of a toggle switch. You will use a case structure to handle
the logic of which signal is output and a While Loop to keep the application running until a Stop
button is pressed.
1. Let’s start by placing a While Loop on the block diagram. Draw it large enough to
accommodate the other code you will be placing inside it. You can locate the While Loop
on the Express»
Execution Control palette as shown below.
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2. Next select the Case Structure from the Execution Control palette and place it inside the
While Loop as shown below.
3. Next we will add the simulate signal VIs two the case statement. Remember one will
output a triangle wave, the other a sine wave. From the Express»Input palette, select
Simulate Sig as shown below, and place it inside the case statement.
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4. Configure the first Simulate Sig to produce a triangle wave by selecting the Signal type
as shown below.
5. Your block diagram should now look like the following.
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6. Next, switch the case statement from True to False, as shown below.
7. Repeat steps 3 and 4, except this time leave the default settings for the Simulate Sig VI
so it will generate a sine wave.
8. Switch to your front panel and place a Waveform Graph as shown below.
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9. Also add a vertical toggle switch from the Boolean palette to the front panel as shown
below.
10. Your front panel should look like the following.
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11. Switch back to the block diagram and wire the toggle switch to the input of the case
statement as shown below.
12. Next, wire the outputs from both of the Simulate Signals to the waveform graph. Note
that you will have to wire through the wall of case statement. Don’t forget wire both the
cases, True and False.
13. You are ready to test your VI by switching the toggle switch back and forth. You should
see the graph switch between a sine and triangle wave.
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Adding Digital Output to Your Project
Often when you are creating control applications, controlling digital lines is necessary to
interface with pumps, valves, lamps, etc. In the next part of this exercise we will extend our
application to include control of the digital output lines.
8. Right-click on your front panel and select an empty array container as shown below.
9. Place the array container at the bottom of the VI, as shown below.
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14. You can create an array of controls by simply inserting them into the array. Right-click
on the front panel and select a push button from the Boolean palette and drop it into
the empty array.
15. It should look like the following.
16. Next we will increase the size of the array of Booleans so it contains eight elements. To
do this, click on the right side of the array container and drag it to the right until eight
push-buttons are visible.
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17. VERY IMPORTANT STEP- Click on the eighth switch to initialize the array size:
18. Next configure the hardware to recognize these switches and control one digital output
per switch. Start by switching to the block diagram using <Ctrl-E>.
19. Next select the DAQ Assistant from the Express»Output palette
20. In the DAQ Assistant select Digital I/O»Line Output as shown below. Click Next.
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21. Select all the digital output lines by clicking on the first then holding the shift key down
before clicking on the last out, then click Finish.
22. Click OK at the following dialog.
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23. Finally wire the output of the array to the data input on the DAQ Assistant, as shown
below.
24. Switch to the front panel and Run the VI. Use the push buttons to activate the digital
outputs on the NI 9472 module and watch the LEDs change as you select different push
buttons.
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Optional Steps
1. Add logic to the VI so it will stop either when you press the STOP button or when the
loop iterations have exceeded 10,000.
2. Do this by inserting an Or gate from the Boolean palette before the STOP button, as
shown below.
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3. Next select the greater than function from the Comparisons palette.
4. Wire as follows.
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5. Right-click on the open terminal of the greater than block and select Create»Contant.
6. Change the constant to 10000 as shown below and Run the VI.
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7. Finally, open and examine the State Diagram template that ships with LabVIEW. Select
File»New and select Standard State Machine from the list box as shown below.
Examine the comments included on the template. There are several templates such as
this one to help you get started with your LabVIEW applications. Take a few minutes to
familiarize yourself with what is available.
End of Exercise 3
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Exercise 4: Multiple Operations with
Analogue I/O
Exercise Overview
Objective
In this exercise, you will use the DAQ Assistant to build a LabVIEW VI that generates and
outputs an analogue waveform. You will then add a second loop that measures the waveform
using an analogue input channel.
Goals
When you have completed this exercise, you will:
 Know how to generate signals in LabVIEW with NI CompactDAQ
 Run loops in parallel for multiple analogue operations
Exercise Instructions
1. If you closed LabVIEW after the last exercise, launch it. Open a new VI.
2. Press <Ctrl-E> to switch to the LabVIEW block diagram.
3. Browse to the Input subpalette on the Functions»Express palette and click the Simulate
Sig Express VI as shown below. Place the VI on the block diagram.
4. In the Signal section of the window, set Amplitude to 5.
5. In the Timing section of the window, set Samples per second (Hz) to 10,000. Click OK.
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6. Bring up the Functions»Express palette again, and browse to the DAQmx Assist VI on
the Output subpalette of the Functions palette. Place the VI on the block diagram.
7. In the Create New window, select Analogue Output as the Measurement Type and then
select Voltage.
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8. In the next window, click the + sign next to cDAQ1Mod3 (NI 9263), select ao0, and click
the Finish button.
9. In the DAQ Assistant configuration window, select Generate Continuously from the Task
Timing tab in the lower part of the window. Uncheck Use timing from waveform data,
and set the Rate (Hz) to 10,000. Click the OK button.
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10. On the block diagram, move the DAQ Assistant Express VI to the right side of the
Simulate Signal Express VI. Wire the Sine output of the Simulate Signal VI to the data
input of the DAQ Assistant VI. To create a wire, move your cursor over the blue arrow on
the Sine output terminal of the Simulate Signal VI and left-click to start the wire. Move
your cursor to the data input terminal of the DAQ Assistant VI and left-click again to
attach the wire. Your block diagram should resemble the following figure.
11. To make the VI run continuously, create a While Loop. A While Loop causes all parts of
the program inside the loop to run continuously until a Stop button is clicked. To create
the While Loop, browse to the Exec Ctrl subpalette of the Functions palette and select a
While Loop.
12. Draw the While Loop around your entire block diagram. Your block diagram should
resemble the following figure.
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13. To create a slide control for varying the frequency of the sine wave, press <Ctrl-E> to
switch to the LabVIEW front panel. Right-click on the empty gray space to pull up the
Controls palette. Select Vertical Pointer Slide from the Numeric Controls subpalette of
the Controls palette. Place the vertical pointer slide on the front panel.
14. Right-click the slide control and select Properties. On the Appearance tab, change the
label to Frequency. On the Scale tab, change the Scale Range so Minimum equals 0.00
and Maximum equals 1000.00. Click OK to close the Properties window.
15. Press <Ctrl-E> to switch to the block diagram. Notice the orange Frequency slide control
terminal. Move the control inside the While Loop to the left side of the Simulate Signal
Express VI. Wire the knob control to the Frequency input terminal of the Simulate Signal
Express VI (the second orange arrow on the left side of the Simulate Signal Express VI).
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Note: Make sure that you wire the knob control to the correct input terminal of the
Simulate Signal Express VI. If you make a bad wire connection, double-click the wire to
select it and press <Delete>.
Your block diagram should resemble the following figure.
16. This VI will now use the frequency knob on the LabVIEW front panel to generate a sine
wave at the specified frequency. This sine wave is then generated on analogue output
channel 0 of the NI 9263 C Series module by the DAQ Assistant Express VI.
17. Save the VI as Analogue output.vi in the Desktop\CustomerWork folder.
18. Increase the size of the block diagram window to make space for another While Loop to
go below the existing Analogue Output code.
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19. Place a DAQ Assistant Express VI from the Input subpalette of the Functions»Express
palette. Select Analogue Input as the Measurement Type and select Voltage. In the next
window, expand channels of the cDAQ1Mod2 (NI 9215) by selecting the + sign, and
select ai0. Click the Finish button.
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20. In the DAQ Assistant window, select Acquire Continuously from the Task Timing tab in
the lower part of the window. Set the Rate (Hz) to 10,000 and click OK.
21. Once you click OK, a dialog window will appear asking if you would like to create a While
Loop around the DAQ Assistant. Select Yes to automatically create a While Loop for this
continuous acquisition.
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22. The block diagram should resemble the figure above. Next, create a graph indicator to
display the analogue input data. To create a graph indicator, right-click the data output
terminal of the DAQ Assistant Express VI, and select Create Graph Indicator.
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23. Below is a picture of the completed block diagram.
24. Press <Ctrl-E> to switch to the LabVIEW front panel.
25. Locate the stop (F) Push Button control and right-click to replace it with a Stop Button
control, as shown on the diagram below. (Replace»Boolean»Stop Button)
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26. Rearrange the front panel controls and indicators to resemble the figure below.
27. Save the VI as Analogue Input and Output.vi in the Desktop\CustomerWork
folder.
28. Run the VI
29. The analogue output loop is generating a sine wave on analogue output channel 0,
which is wired directly to channel 0 of the analogue input module. Use the slider control
on the front panel to control the sine wave frequency, and look at the graph on the
front panel to monitor the sine wave.
30. Press both stop buttons to stop the execution of both loops.
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Beyond the Exercise
For Loops can be used to generate arrays using a feature called automatic indexing, as shown in
the following figure.
Try building the following block diagram to further manipulate the waveform being generated.
End of Exercise 4
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