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

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

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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