11/28/2018
INTRODUCTION TO
Virtual Reality
1
11/28/2018
First Person Perspective (FPP)
Course outline
• EXPERIMENTATION THROUGH GRAPHICAL
PROGRAMMING: Introduction, the front
panel, the block diagram, data acquisition,
components of a DAQ system, DAQ hardware
configuration, DAQ assistant, analog I/O,
digital I/O, typical sensor interface examples.
2
11/28/2018
Learning objectives
• Be able to
– Appreciate the knowledge on virtual instrumentation
– Know the process of data acquisition
– Design a graphical programming language for smart home
and automation applications
DAQ
• Data acquisition involves measuring signals (from a real-world
physical system) from different sensors, and digitizing the
signals for storage, analysis and presentation.
• Data acquisition is the digitizing and processing of multiple
sensor or signal inputs for the purpose of monitoring, analyzing
and/or controlling systems and processes.
3
11/28/2018
What type of signals?
• Signal - Time-varying “quantities”
(voltage) which convey some sort of
information (ie. voltage that’s changing
over time)
Analog – continuous
Digital - discrete
Analog to Digital conversion
Converts analog signals into binary
Encoding - assigning a
Quantizing - breaking down analog value is a digital word or
set of finite states number to each state
and matching it to the
input signal
Example
Input analog signal :0-10 V
The number of possible states that the converter
can output is: Analog quantization size:
N=2n Q=(Vmax-Vmin)/N = (10V – 0V)/8 = 1.25V
where n is the number of bits in the AD converter
Example: For a 3 bit A/D converter, N=23=8.
4
11/28/2018
Output Discrete Voltage Output Output Binary
States Ranges (V) States Equivalent
0 0.00-1.25
0 000
1 1.25-2.50
1 001
2 2.50-3.75
2 010
3 3.75-5.00
3 011
4 5.00-6.25
4 100
5 6.25-7.50
5 101
6 7.50-8.75
6 110
7 8.75-10.0
7 111
Resolution
• Resolution (number of discrete values the converter
can produce) = Analog Quantization size (Q)
(Q) = (Vmax-Vmin)/ N
• Q = 1.25V, this is a high resolution. A lower
resolution would be if we used a 2-bit converter,
then the resolution would be 10/2^2 = 2.50V.
5
11/28/2018
Sampling Rate
Frequency at which ADC evaluates analog signal.
As we see in the second picture, evaluating the signal more often more
accurately depicts the ADC signal.
Signal conversion
6
11/28/2018
NI USB 6008
NI USB 6009
Input and Output ports
7
11/28/2018
labVIEW
(Laboratory Virtual Instrumentation
and Engineering Work bench)
Virtual Instrumentation (VI)
• To Test, Control and Design applications making
accurate analog and digital measurements.
• Using VI, can also control external hardware
devices from desktop computer and for displaying
unit.
User Interface-Display and Control
Processing Module Data Base
Interface
Sensor Module
Sensing (or
Transducer) Sensor Interface
Signal conditioning
A/D conversion
8
11/28/2018
LABVIEW-Introduction
• Lab VIEW is a graphical programming language (G) that
uses icons instead of lines of text to create applications.
• Lab VIEW Programs Are Called Virtual Instruments (VIs)
because their appearance and operation imitate physical
instruments like Volt meter, Digital Multi-meter.
• Lab VIEW contains a set of VIs and functions for acquiring ,
analyzing , displaying and storing data.
• It includes analysis functions for differential equations,
optimization, curve fitting, calculus, linear algebra, statistics
and so on.
User – Interface
• Front Panel
• Controls = Inputs
• Indicators = Outputs
Ctrl+T = Align panels
• Block Diagram
• Accompanying
“program” for front
panel
• Components “wired”
together
9
11/28/2018
VI Front Panel
Front Panel Icon
Toolbar
Boolean
Control Graph
Legend
Waveform
Graph
Plot Scale
Legend Legend
VI Block Diagram
Block
Diagram
Toolbar Divide
Function
SubVI
Graph
Terminal
Wire
Data
While Loop Numeric Timing Boolean Control
Structure Constant Function Terminal
10
11/28/2018
Controls and Functions Palettes
Controls Palette
(Front Panel Window)
Select View» Controls Palette or
right-click the front panel
workspace to display the
Controls palette.
Functions Palette
(Block Diagram Window)
Arithmetic, instrument I/O,Timing, and
data acquisition operations.
Status Toolbar
Run Button
Continuous Run Button Additional Buttons on
the Diagram Toolbar
Abort Execution
Pause/Continue Button Execution Highlighting
Button
Text Settings
Step Into Button
Align Objects
Step Over Button
Distribute Objects
Step Out Button
Reorder
Resize front panel
objects
11
11/28/2018
Types of Controls and
Indicators
Loops
• Nearly all programs involve some
sort of loop where all or sections of
the program must be repeated.
FOR Loop WHILE Loop
12
11/28/2018
NI – DAQmx
NI - DAQmx
13
11/28/2018
14
