Download - Report of MI CL23
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1.0 ABSTRACT
In cooperative learning 2, we are using the experiment of a spring mass system to
learn about the concept of virtual instruments in DASYLab environment by link the
DASYLab to data acquisition system (DAQ) and to an accelerometer to measuring some
engineering quantity and understand the type of tools in software when undergo signal
processing. So that, the new engineer have capable to adapt themselves and responds to
various challenges of highly competitive, global economy. The theory is to study the
fundamental characteristics of measurement systems based on digital processing such as
convert the engineering quantity into electrical signal and analyze it. Its objective is to
point out the characteristics and the features related to issues of accuracy, precision, and
sensitivity, so as to achieve a better understanding of the effective usability of these
technologies software to present and discuss the significant result acquire from the
transducer, and promote the best use of these advanced, powerful method. It is discover
that in the case of studied, although the result was succeeded recorded and display based
on the digital processing but still have some of the problems needed to discuss such as we
decided whether to use the signal that is filter or not to perform the windowing function.
The existing problems contribute in this cooperative learning 2 are identified and the
solutions are outlined.
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TABLE OF CONTENTS
No. Contents Page(s)1.0 Abstract 12.0 Acknowledgement 33.0 Introduction 44.0 Problem Statement 85.0 Objectives 96.0 Methodology
- Flow chart10
7.0 Procedures 128.0 Results & Discussions
a) Displaying time trace in accelerationb) Convert time trace from acceleration to velocityc) Computing statistical values (std. deviation, mean and RMS)d) Converting time trace to spectrum and display in frequency domaine) Windowing functionsf) Effects of using different block size (1024 to 8192)g) Trigger functionh) Display in different layouts and using ‘Switch’ function to switch from one layout to another
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9.0 Conclusion 2310.0
References24
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2.0 ACKNOWLEDGEMENT
Our group member would like to take this opportunity to thank a few people as
well as those who have contributed to the success of this final project whether directly or
indirectly.
First and foremost, we would like to express our highest gratitude to our lecturer,
Mr Mohd Hafizi Bin Zohari for his continuous guidance and teachings. Without his
effort, this cooperative learning project would not have been this perfect and completed
within the time frame given.
Next, a thousand of thanks to my group members for their full cooperation and
commitment in helping to complete the research project until it is a total success. Without
their efforts and commitment; this research project would definitely be a failure.
Last but not least, we would like to really thank all those people who have
contributed to the success of this research project whether directly or indirectly. Finally,
we wish all of the contributors a good health. Thank you.
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3.0 INTRODUCTION
Accelerometer
Accelerometer is the sensor that we study for our BMM3532 Measurement and
Instrumentation CL2 project. Accelerometer is a sensor that measure proper acceleration
forces. The force measure by the accelerometer may be static like the constant force of
gravity which are caused by moving or vibrating the accelerometer. The force caused by
vibration or a change in motion (acceleration) causes the mass to "squeeze" the
piezoelectric material which produces an electrical charge that is proportional to the force
exerted upon it. Since the charge is proportional to the force, and the mass is a constant,
then the charge is also proportional to the acceleration. The force is detected by the
sensor and changed the physical signals to electric signals. Accelerometer has many
applications in industries. For example, accelerometers are components of inertial
navigation systems for aircraft and missiles. Accelerometers also used to detect vibration
on a rotating machinery. Furthermore, accelerometers also used in phone and tablets to
make sure the screens are always display upright. Micro-machined accelerometers are
increasingly present in portable electronic devices and video game controllers, to detect
the position of the device or provide for game input. Accelerometers also used in cars to
detect vibration in car body or car parts.
Accelerometer
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Data Acquisition System (DAQ)
Data acquisition is the process of collecting or sampling signals from the real physical
condition and converting the samples into digital numerical values that can read by
computers. Data acquisition (DAQ) also measures an electrical signal such as voltage,
current, temperature, pressure, or sound with a computer. Data acquisition system
converts the analog waveforms into digital values for processing.
Basically there are some important components in data acquisition system include:
Sensor - converts physical signals to electric signals
Signal conditioning – convert sensor signals into a form that can be read or
converted to digital values.
Analog to digital converters- convert the conditioned signal sensor to digital
values.
DAQ system
Virtual Instrument Software (DASYLab)
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DASYLab is a computer software that allow us to interactively develop PC-based
data acquisition applications. DASYLab helps to create custom graphical application.
Measurement instrument like frequency analyser, analog input/output, digital
input/output, oscilloscope, signal analysis hardware in computer software. It save time
and cost because we does not need to buy the measurement instrument separately and
measure it manually to get the signal data. DASYLab allows to create complex
applications without programming. DASYLab make our life easier by providing all the
chart, graphs and digital value meter that shows the result of the measurement and signal
data.
How the Sensor, DAQ system and Virtual Instruments Software work
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Sensors like accelerometer detect or measure the acceleration. The sensors then
will convert the physical signals to electric signals. The obtain data or electric signals
from the accelerometer sensor will then transfer to Data Acquisition system like National
Instrument (NI) device. Data Acquisition System device have signal conditioner,
amplifier, anti-aliasing Filter, USB communication, analog-to-digital converter, and etc.
First process in Data Acquisition System is signal conditioning circuitry, where the signal
receive from the sensor is converted into suitable form for input into analog-to-digital
converter. The signal conditioning circuitry process can involve filtering, amplification,
and etc. Then, the analog to digital converter convert the analog signal to digital signal so
that can read by digital equipment such as computer. The digital signals is send through
computer usb bus to computer that have software like DASYLab and LABView that can
control the DAQ system and storing the data from the signal. The result can be shown in
numerical value or charts and graphs in the computer.
4.0 PROBLEM STATEMENT
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The experiment of spring mass system was using to link the DASYLab to data
acquisition system and an accelerometer to measure some engineering quantity and
determine engineering unit for measurement and the sensitivity of the sensor. The 2000
sample/sec as sampling frequency is chosen to perform the virtual instrument.
The DASYLab is used:
To display the time trace in acceleration with correct unit and using the
integrator and filter to convert it to velocity time trace.
To compute statistical values for standard deviation, root mean square and
mean and display in digital meter.
To perform Fast Fourier Transform analysis to covert the time trace spectrum
and display in frequency domain.
To show the effect of input signal by using the windowing functions such as
Rectangular, Hanning and Flat Top for block size from 1024 to 8192.
To trigger one block at a time and display each instrument in different layout
by using the ‘switch’ function.
5.0 OBJECTIVES
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To learn and familiar with virtual instruments software (DASYLab)
To understand principle of working of the sensor with DAQ system and virtual
instruments software
To develop the virtual instruments software set-up based on the chosen mechanism
of accelerometer in the lab
6.0 METHODOLOGY
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The progress of our project is summarized in the table, Gantt chart and Flow chart below:
Week(s) Activities Contents
8 - Brainstorming - Discussion among members had been carried out to
discuss the ideas to conduct this assessment.
9 -Reseaching and
testing DasyLab
-Research the virtual instruments software
(DASYLab) and its function.
10, 11
and 12
- Developing set-up in
DasyLab
- Collect and analyzing
data.
-Develop virtual instrument using DASYLab
Data
- Displaying Time Trace in acceleration
-Convert the time trace from acceleration to velocity
using an integrator and filter
- Computing statistical values and display in DigitalMeters
- Converting time trace to Spectrum and display in frequency domain using Fast FourierTransform analysis
-Show the effects of using windowing function
- Effects of using different block size
- Use trigger function to trigger time trace one block
at a time
- Display each instrument in different layouts and
using Switch function switching each layout to
another
13 -Preparing report The data is analyzed and preparing project report.
14 -Submitting report -The finished report is submitted.
Flow Chart
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7.0 PROCEDURES
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Brainstorming
Researching and testing DASYLab
Developping set-up in DASYLab
Collect and analyze data
Preparing project report
Submitting Report
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National Instruments Measurement & Automation Explorer (NI-Max) Setup
1. ‘National Instruments Measurement & Automation Explorer’ was opened and ‘Data Neighborhood’ was selected and clicked.
2. The space ‘Create New…’ was clicked to create a new task.
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3. NI-DAQmx Task was double-clicked.
4. ‘Acquire Signals’ was chosen and ‘Analog Input’ of ‘Acceleration’ was selected.
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5. The model of National Instruments was checked (NI 9234) and the ‘ai0’ was selected as the ai0 port was connected to the sensor (accelerometer).
6. A task name was inputted.
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7. The scale unit was changed to m/s^2 (for acceleration) and the sensitivity was set at 106 which was measured by lab assistant and shown on the table for the sensor.
8. The button ‘Run’ was pressed to let the acceleration graph running and the graph was stopped using ‘Stop’ button. The button ‘Save’ was pressed to save the data before proceeding to DASYLab.
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DASYLab Setup
1. The data saved in NI-Max was inputted to DASYLab with analog input.
2. Y/t chart was used to connect to analog input to display time trace in acceleration (red colour in picture).
3. Filter and integrator were used to convert acceleration to velocity and displayed with a Y/t chart (orange colour in picture).
4. Statistical values was used to compute standard deviation. Mean and RMS of acceleration and they were displayed using Digital meter (yellow colour in picture).
5. FFT (Fast Fourier Transform) and data windowing were used to compute time trace to spectrum and it was displayed in frequency domain using Y/t chart (green colour).
6. The effects of windowing (Rectangular, Hanning and Flat Top) were using data windowing for different block size from 1024 to 8192 (blue colour).
7. Data Trigger (Pre/Post Trigger) was used to trigger time trace one block at a time (purple colour).
8. Layouts were designed and they were switched from one layout to another using ‘Switch’ function (indigo colour).
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9. The sampling frequency was set to 2000 as stated in question paper.
10. Finally, the data were obtained.
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8.0 RESULTS & DISCUSSIONS
a) Displaying time trace in acceleration
This is the acceleration time trace before filtered. It is like a sinusoidal curve for acceleration.
b) Convert time trace from acceleration to velocity using integrator and filter
The filtered curve becomes smooth compared to before filtering.
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c) Computing statistical values and display in Digital Meter
These are the values obtained for standard deviation, mean and RMS for the acceleration.
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0.04
2.13
1.43
MAXIMUM
MINIMUM
RMS
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d) Converting time trace to spectrum and display in frequency domain
This is the frequency domain we obtained. We used FFT to transform time domain into frequency domain.
e) Show the effects of using windowing functions (Rectangular, Hanning and Flat Top)
f) Effects of using diffent block size (1024 to 8192)
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-Windowing is a process of ‘forcing’ the end points of a time frame to zero. This will get rid of the leakage. As we can see from the result, the curves of the end points are forced to zero for all the block size.
- Flattop window gives better amplitude accuracy than Hanning window. The result we obtained is correct. Meanwhile for Rectangular window, it gives the best balance between Hanning and Flat Top.
What is the difference between Windowing a block size 1024 and 8192
What we saw is that block size 8192 moves much slower than block size 1024. For more details, block size 1024 moves every 1 second and you can see the amplitude whereas for block size 8192, you can only see the amplitude every 5 second. This is because the samples for block size 8192 is bigger and it needs longer time to analyze.
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g) Use Trigger function to trigger time trace one block at a time
We got a rectangular block after trigger function.
h) Display result in layouts and use Switch function to switch one layout from one to another
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The blue colour background is actually the layout. The NEXT button at bottom is created using Switch function to press the Next and it can switch to next layout.
9.0 CONCLUSION
In conclusion, we have researched and learnt how to use virtual instruments software DASYLab. We successes to develop the virtual instrumentation system set up based on mechanism of accelerometer in the vibration laboratory. We choose experiment of mass spring system as our project by using DASYLab. We are able to connect Data Acquisition System (DAQ) to the sensor used which is accelerometer to measure the engineering quantity. We learnt how the sensor works with DAQ system and the virtual instruments software. The objectives had been achieved.
10.0 REFERENCES
[1] Lecture notes BMM3532 Measurement and Instrumentation
[2] http://en.wikipedia.org/wiki/Window_function
[3] http://en.wikipedia.org/wiki/Database_trigger
[4] DASYLab® (Data Acquisition System Laboratory) user guide, version 7.0, http://highered.mcgraw-hill.com/sites/dl/free/007292201x/206542/0000015918.pdf
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