study of environment based condition of ...

STUDY OF ENVIRONMENT BASED CONDITION OF ELECTROMAGNETIC INTERFERENCE DURING ECG ACQUISITION

WONG WEI YUN

UNIVERSITI TEKNOLOGI MALAYSIA

PSZ 19:16 (Pind. 1/07)

UNIVERSITI TEKNOLOGI MALAYSIA DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT Author’s full name :

WONG WEI YUN

Date of birth

:

7 MARCH 1988

Title

:

STUDY OF ENVIRONMENT BASE CONDITION OF ELECTROMAGNETIC INTERFERENCE DURING ECG ACQUISITION

Academic Session :

2010/2011

I declare that this thesis is classified as:

I acknowledged that Universiti Teknologi Malaysia reserves the right as follows: 1. The thesis is the property of Universiti Teknologi Malaysia. 2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose of research only. 3. The Library has the right to make copies of the thesis for academic exchange: Certified by :

______________________________ SIGNATURE

880307-52-6356 (NEW IC NO. / PASSPORT NO.)

Date: 3rd MAY 2011

________________________________ SIGNATURE OF SUPERVISOR

Dr. Rubita binti Sudirman NAME OF SUPERVISOR

Date: 3rd MAY 2011

I declare that I have read this work and in my opinion this work is adequate in terms of scope and quality for the purpose of awarding a degree of Bachelor in Electrical Engineering (Medical Electronics)

Signature

:

_______________________

Name of Supervisor :

Dr. Rubita binti Sudirman

Date

3rd May 2011

:

STUDY OF ENVIRONMENT BASED CONDITION OF ELECTROMAGNETIC INTERFERENCE DURING ECG ACQUISITION

WONG WEI YUN

Submitted to the Faculty of Electrical Engineering in partial fulfilment of the requirement for the degree of Bachelor in Electrical Engineering (Medical Electronics)

Faculty of Electrical Engineering Universiti Teknologi Malaysia

MAY 2011

ii

I declare that this thesis entitled “Study of Environment Based Condition of Electromagnetic Interference during ECG Acquisition” is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.

Signature

: __________________

Author’s Name

: WONG WEI YUN

Date

: 3rd MAY 2011

iii

This thesis is specially dedicated to

My beloved family and friends

For their endless support, encouragement, inspiration and motivation Throughout my academic career

iv

ACKNOWLEDGEMENTS

First of all, I would like to take this opportunity to express my deepest appreciation to my supervisor, Dr. Rubita binti Sudirman for her guidance and support throughout this project.

Besides, I would like to express my thankfulness to many friends, for their inspirational assistance and supervision during this project. Working with them was indeed a wonderful and learning experience, which I thoroughly enjoyed.

Last but not least, my deepest love and thanks go to my family who always give encouragement and care during my four years studies in Universiti Teknologi Malaysia.

v

ABSTRACT

The electrocardiograph signal or known as ECG signal is an electrical signal that generated naturally from our heart beat. The signal is commonly used for diagnosis or examining the heart disease. It has a principle measurement range of 0.5 to 4 mV and 0.05 to 100 Hz for its signal frequency.

The ECG system basically is

implemented through combination of instrumentation amplifier and some filter. The ECG signal is easily disturb by the Electromagnetic Interference (EMI) of the environment. It is the most headache problem of the advance ECG system. The EMI will affect the patient heart beat data and cause the inappropriate treatment decision made by the doctor. This small error may cause the death of the patient. Hence, this is a study of environment based condition of Electromagnetic Interference during ECG acquisition. The study is mainly focusing to determine which environment in the surrounding provides the most EMI. So, experiment to determine the effect of EMI was done at several places. Portable ECG circuit using a 9 V battery as the power supply is designed so that for purpose of mobility to take ECG signals.

Analysis was done to the ECG data that have been taken from

different environment. Different environment provide different EMI effect to the ECG signal. The environment of lab that consists of many electronic devices will emitted EMI which will give noise to ECG signal. But, the noise did not affect the ECG patient data. While, the EMI that emit by mobile phone is seriously affecting the ECG patient data. From the project, there is analysis shown that the more advance and expensive mobile lesser EMI effect to the ECG patient data.

vi

ABSTRAK

Isyarat elektrokardiogram (EKG) adalah isyarat elektrik yang dijanakan dalam badan orang secara semula jadi.

Signal itu biasanya digunakan untuk diagnosis atau

mengkaji penyakit jantung. Lingkungan ukurannya adalah daripada 0.5 hingga 4 mV manakala lingkungan frekuensinya adalah dalam lingkungan 0.05 hingga 100 Hz. EKG sistem dibina daripada pengabungan penguat instrumentasi dan beberapa jenis penapis. Isyarat EKG adalah senang dipengaruhi oleh gangguan elektromagnetik di sekitar kita.

Ia merupakan masalah yang paling merisaukan sebab gangguan

elektromagnetik akan mempengaruhi data EKG pesakit. Kesalahan data EKG akan menyebabkan doktor tersalah dalam menganalisis penyakit pesakit tersebut. Masalah yang nampak kecil ini akan membawa kepada kematian. Oleh itu, analisis tentang pengaruh gangguan elektromagnetik dari persekitran kepada isyarat EKG harus dijalankan. Projek itu menumpu pada mengenal pasti keadaan persekitaran yang manakah akan membawa kepada pengaruh elektromagnetik yang paling tinggi. Maka, EKG litar yang menggunakan bateri 9 V dan senang dibawa harus dibina. Analisis boleh dilakukan dengan merujuk kepada data EKG yang diambil dari tempat yang berlainan. Persekitaran yang berlainan akan membawa kesan yang berbeza kepada isyarat EKG. Dalam keadaan persekitaran yang penuh dengan peralatan elektronik akan memberi impak kepada isyarat EKG dengan menambahkna hingar dalam isyarat tersebut, tetapi hingar tersebut tidak mempengaruhi data EKG penyakit. Manakala, pengaruh elektromagnetik daripada telefon bimbit akan mempengaruhi data EKG pesakit. Daripada projek yang dijalankan, analisis menunjukkan telephone bimbit yang lebih mahal dan modern akan memberi impak yang kurang kepada isyarat EKG.

vii

TABLE OF CONTENT

CHAPTER

TITLE PAGE

1

2

DECLARATION OF THESIS

ii

DEDICATION

iii

ACKNOELEDGEMENT

iv

ABSTRACT

v

ABSTRAK

vi

TABLE OF CONTENT

vii

LIST OF TABLES

ix

LIST OF FIGURES

x

LIST OF APPENDICES

xi

INTRODUCTION 1.1

Background

1

1.2

Problem Statements

2

1.3

Objective of project

2

1.4

Scope of project

3

1.5

Report Outline

3

1.6

Summary of works

4

LITERATURE REVIEW 2.1

ECG signal

7

2.2

Standard Lead of ECG

9

2.3

Portable ECG device

10

2.4

LaBVIEW

11

viii

2.5

Impact of Electromagnetic Interference to

13

Environment 2.6

Impact of Electromagnetic Interference by Mobile Phone

3

METHODOLOGY 3.1

Introduction

15

3.2

Implementation of Hardware

16

3.2.1 ECG Simulator

17

3.2.2 NI USB 6009

18

3.2.3 ECG Circuit

20

Implementation of Software

24

3.3

4

5

RESULT AND DISCUSSION 4.1

Introduction

4.2

Experiment: Analysis the Effect of Environment

28

to the EMI during ECG Acquisition

28

4.2.1 Procedure

29

4.2.2 Experimental Result Analysis

29

CONCLUSION AND RECOMMENDATION 5.1

Conclusion

36

5.2

Recommendation

36

38

REFERENCES

APPENDICES

14

A- B

40-59

ix

LIST OF TABLES

TABLE NO.

TITLE

PAGE

1.1

Gantt chart of the project semester 1

5

1.2

Gantt chart of the project semester 2

6

4.1

Relation between different environment and ECG signal

29

4.2

Relation between different phone environment and ECG

4.3

signal

31

Relation between environment and amplitude of PQRST

33

x

LIST OF FIGURES

FIGURE NO.

TITLE

PAGE

1.1

Flow chart of the work

4

2.1

Sample of single beat ECG signal

8

2.2

Standard Lead & Einthoven Triangle

9

2.3

LabView front Panel

12

3.1

Block diagram of project

15

3.2

Overview of the project

16

3.3

ECG 200

17

3.4

NI USB 6009 Data Acquisition

18

3.5

Analog terminal of NI USB 6009

18

3.6

Analog input circuitry

18

3.7

Analog output circuitry

19

3.8

ECG circuit diagram

19

3.9

ECG circuit

20

3.10

Circuit of voltage comparator

20

3.11

Circuit of amplifier of ECG

21

3.12

Instrumentation Amplifier INA121

22

3.13

Block diagram of the 1st program in LabVIEW

23

3.14

Front panel of the 1st program in LabVIEW

24

3.15

Block Diagram of the 2nd program in LabVIEW

25

nd

3.16

Front panel of the 2

program in LabVIEW

25

4.1

Experiment with ECG circuit

26

4.2

PQRST Signal

31

4.3

Graph Amplitude of PQRST vs. Environment

33

xi

LIST OF APPENDICES

APPENDIX

TITLE

PAGE

A

Datasheet and circuit design for hardware

40

B

Block diagram for software of LaBVIEW

57

CHAPTER 1

INTRODUCTION

1.1 Background

Electrocardiogram (ECG) is the test which measures the electrical activity of the heart. The heart is a muscular organ that beat in rhythm to pump the deoxygenated or oxygenated blood through the whole body. The heart’s beating rhythm generate the electrical signal called ECG signal. On the 1895, the 1st accurate recording ECG has successfully invented. The ECG device is invented to detect and record the ECG signal which used by doctor for taking further treatment. It is very important in clinical diagnosis for the heart disease.

Furthermore, it provide an objective

indicator for the correct analysis, diagnosis, treatment and care of heart [1]. Due to the important value of ECG, it has a very wide range of application. Hence, there are many researches on ECG to make it more advances and developed in recording, processing and diagnosis signal. Recently, Singapore has come out with an ECG mobile phone named EPI life. It can be get by purchase USD $358 in the market. The ECG device becomes more advance and keep developing, but there still have problem of interference in its signal.

Normal human ECG is a non-stationary,

nonlinear and low signal to noise ration.

On the other hand, it has principle

measurement in the range of 0.5 mV to 4 mV and its frequency is 0.05 Hz to 100 Hz. Hence, there are many factors that should be taken into consideration in

2 the design of an ECG amplifier, such as the frequency distortion, saturation distortion, interference. In addition, environment, equipment or human factors are also easily affecting the ECG signal. From all of that, the worst is Electromagnetic interference (EMI). It has high impact to the ECG signal during acquisition. The ECG device is fulfilling with many advance function but its clinical consequence still remains controversial. Hence, there is need to carry on a study to determine which environment will give high impact of EMI to the ECG signal. From there, it can ease the researcher to find out a solution to cure the problem of EMI to ECG signal.

1.2

Problem Statement

Nowadays, ECG device is very developing and advance in its application. However the problem of the EMI still exists in the ECG signal. The EMI will cause the ECG device having less accuracy in producing the data. Hence, there is error in the patient’s data reading. The error will lead to the delay or inappropriate treatment decision made by the doctor. It would not bring too big problem to the normal people but it will cause death to the patient who are seriously injured or the patient who in emergency. So we should take serious with this problem.

1.3

Objective of Project

The main core of this project is to study the environment based condition of EMI during ECG acquisition. This can be explained in other words, analysis the effect of the EMI from the environment to the ECG signal. The second objective is to design a portable ECG amplifier. It is use to collecting the ECG signal for analysis purpose.

3 Due to the need to take the ECG signal in different environment, hence the ECG system must be portable.

1.4

Scope of Project

In order to achieve the objectives of the project, there are several scopes that have being identified. Firstly, implementation of a portable ECG circuit is needed. Then, ECG signal data recording is taken at different places and room conditions to test the EMI of ECG signal. Signal was study showed that an EMI will affect the ECG signal. Hence the experiment is done to acquire the ECG signal and analyses the entire ECG signal to determine the effect at different condition or environment.

1.5

Report Outline

The thesis is organized into 5 chapters. The thesis is start with an introduction which gives a simple overview the background of the project. Then, follow by other 4 chapters which explain the project in more detail.

Chapter 2 cover up the literature review part which focusing on the understanding of implement a portable ECG circuit, effect of EMI and effect of environment to the ECG signal.

Next, Chapter 3 briefly is about the methodology of the hardware and software of the project. It discussed the methods that use to implement the hardware and software.

4 The result and discussion is presented in Chapter 4. All the data that have been collect will be analysis and discuss in this chapter.

Last but not least, Chapter 5 discussed about the conclusion and recommendation.

1.6

Summary of Works

The works of the project can be summarized into the flow chart as shown in Figure 1.1 and Gantt chart as shown in Table 1.1 and Table 1.2.

Literature review Design portable ECG circuit Taking ECG signal at different environment with labView Analysis the Signal Report writing Figure 1.1: Flow Chart of the work

5

Table 1.1: Gantt chart of the project semester 1

Weeks 1. Tasks 2. Literature review 3. Methodology 4. Choosing Component 5. Designing ECG simulator circuit 6. Run ECG circuit schematic in Multisim 7. Presentation of proposal 8. Report writing

1 2 3 4 5 6 7 8 9 10 11 12 13 14

6

Table 1.2: Gantt chart of the project semester 2

1. Tasks 2. Implement the Circuit in strip board 3. Collecting the signal of ECG at different environment 4. Analysis the signal 5. Presentation & demo 6. Report writing

Weeks 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16-20

CHAPTER 2

LITERATURE REVIEW

2.1

ECG Signal

The heart is the most vital organs within the human body. It play the role as the pump which circulates oxygenated blood and deoxgenated blood around the body in order to keep in functioning. The waste product generated from the body will remove through the circulation. The electrical activity of the heart can be interpreted into ECG signal through the electrocardiogram recording [2] as the ECG signal is the naturally generated through human body. The ECG is the recording on the body surface of the electrical activity generated by cardiac muscle. When the electrical changes, human body will give raise the currents to whole body that we can regard as a volume conductor; the ECG therefore can be recorded from electrodes attached to skin.

Its has a principle measuremnt range of 0.5 to 4 mV and frequency range of 0.05 to 100 Hz [3]. By detecting the volatge created by the heart beating, its rate can be easily use to observed and used for health purpose. The timing for the PQRST signal can be use to determine the heart disease. Figure 2.1, shows a sample of single beat ECG signal produced by the heart. There are 5 identifiable features in

8 an ECG signal which reperesent the different polarisation stages that make up a heart beat.The deflections are denoted by the letters P, Q, R, S and T.

R Atrial

Venticular

Recovery

activation

activation

wave

S T Atrial depolarization

PR

Ventricular repolarization

Q

Ventricular repolarization

Figure 2.1: Sample of single beat ECG signal

Every identifiable features have their own symbolic function. The P wave is the period of contraction of the atria, Q, R and S wave – QRS interval (also called QRS complex). Besides, the QRS complex also known as the contraction of ventricles. The P wave represent the spread of electrical activity over the atrium and normallys is last less than 0.11 seconds [4]. While the PR interval are in the range of 0.12 to 0.2 seconds in length, it start in the beginning of the P wave until the beginning of QRS complex. The time is depending to the electrical wave through AV nodes. The slower the electromagnetic wave go through the AV node, the prolong the time of PR interval or vice versa.

9 Following with PR is the QRS complex which represent activation of the ventricle. It is a special conductiong bundles spread the wave of depolarization rapidly over the ventricle [4]. Length of QRS normally is less than 0.10 seconds and it indicates some blockage of electrical action in the conductiong system. The first upward in QRS is R wave while the first downward of QRS is called Q wave. R is the stage of activation of ventricle while Q represent activation of the ventricular septum and the electricity is spreading from right to left side through the septum. Q waves indicate either myocardial infarction or obstructive septal hypertrophy [4]. ST segmnet is stage of contracting ventricle but there is no electricity flowing through.

Next, T wave represent the wave when the ventricle prepare to fire again or in other word beginning of the period of rest. In some individuals, there is a small peak occurs at the end or after the T wave which called as U wave. It is due to slow repolarization of the papillary muscles.

2.2

Standard Lead of ECG

LEAD

LEAD II

LEAD III

Figure 2.2: Standard Lead and Einthoven Triangle

10 Figure 2.2 shows the standard lead and the Einthoven Triangle. The three standard limb leads are bipolar leads, which mean they measure the potential difference between pairs of electrodes placed on the arms and left leg. Although there is a lead placed on the right leg, it serves as an electrical ground.

The Einthoven Triangle history is briefly introduced within the following explanation. In 1901, Willem Einthoven developed a ‘String Galvanometer’, an instrument for measuring electric current which able to accurately record the electric activity. Although it was not the first recorder but it was a breakthrough in that it was accurate enough to allow anybody to duplicate the results on the same patient. Einthoven’s system proved to be a great success and soon string galvanometer based ECG system was used in clinical practice worldwide. Since that time the ECG has become a very powerful tool in diagnosing disorders of the heart.

Einthoven stated that the heart is in the center of an equilateral triangle whose apices are the right arm, left arm and left leg. The lead vectors therefore also form an equilateral triangle called Einthoven’s Triangle. The Einthoven’s Triangle is defined as a configuration of three standard limb leads (Figure 2.2). The bipolar limb leads are those designated Lead I, Lead II and Lead III and the three of them often shown by a diagram called the Einthoven Triangle [5]. Lead I go from right to left arm; lead II from right arm to left leg; lead III from left arm to left leg. However, the Lead II is more commonly used. Lead II is the connection which connects amplifier’s non inverting input to the left leg (LL) and connects inverting input to the left arm (LA).

2.3

Portable ECG Device

According to the World Health Organization (WHO), the one of the leading causes of death in the developed world is cardiac disease. The most common method to

11 diagnose the cardiovascular disease (CSD) is using ECG device. Portable mean it is convenient, small size, light can easy to carry. It is a device that everybody can bring it along without any limit location. Hence, a portable ECG device is needed to reduce the number of death due to CSD.

It is not an impossible thing in the developed world as some of the engineer has successfully come out with their design of portable ECG which the prior heart attack and most common abnormal heart rhythms can easily diagnosed [4]. The new device has enable notebook and desktop computer to support family member observing their physiological signal on the screen [5]. The computer can display the ECG signal through National Instrument LabVIEW. User can easily evaluate their health and record the result just by using their computer. It is very convenient to all users.

Besides, the data of ECG can also transmit to the others computer through wireless. Mean, if the patient is taking ECG data at his/ her room, the data also be able be seen by doctor at another room. This has saved a lot of doctor’s time. Recently, Singapore has brought us good news in the health area. They have come out a mobile ECG in market which named as EPI life. EPI life is revolutionary mobile phone device that has integrated multi lead ECG and health suit function [8]. It is well functioning mobile with add in extra specification in recording ECG data. It able to detect our heart beat and ECG signal. There is a links of ECG data with the hospital. In another words, the data will directly sent to the hospital if any defect is detected.

2.4

LabVIEW

LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) is a graphical programming environment used for engineer to develop sophisticated

12 measurement, test, and control system [9]. Commonly, LabVIEW is use to receive, display and process the data and figure out the signal. Besides, LabVIEW helps to create flexible and scalable design and interface with the real word signals.

In addition, it also can be used to analyze data for meaningful information and display the result. From ECG circuit, LabVIEW program has three components which are block diagram, a front panel and a connector pane. When receive the data from serial port, the resource of VISA will use to process and transform the wavelet to find the characteristic points of ECG signal [6]. There is a conjunction device between the hardware and the Labview. Basically purpose of using it is to convert the analog data to digital data. Example of the conjuction devices are NI USB 6008/6009 and wireless device. Figure 2.3 shows the LabVIEW front panel which use to display the ECG signal [10].

Figure 2.3: LabVIEW Front Panel

13 2.5

Impact of Electromagnetic Interference to Environment

Electromagnetic interference (EMI) is a function of power output and frequency of transmitting device [7]. EMI is a self-propagating wave in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation. It is in phase with each other.

Electromagnetic radiation is classified according to the frequency of the wave such as radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

Electromagnetic radiation carries

energy and momentum, which may be imparted when it interacts with matter. Furthermore, it will decrease the distance between transmitting and receiving devices. The signal voltage of ECG is known as very small which in millivolt range. Therefore it is very easy to be influent by the environment.

The application of auto-identification technologies such as radio frequency identification (RFID) also will case the EMI impact to the ECG signal. Examples of the RFID applications in our daily life are price detecting machine and antitheft clips of clothing in shopping center. RFID technology will emit EMI to medical device [13].

The fluorescent light will add a tiny sinusoidal wave which is difficult to filter away [14] will cause the same problem. Moreover, the temperature of the environment will also produce some noise to the ECG signal. For example when the user is cold, the musculature contracts, and this contraction will be taken up by the ECG electrode. Hence there is a noise in signal [15]. The environment issue has effect the ECG signal that generated by our body. Last but not the least, the radios will also giving impact to the ECG signals as it receiving the high radio frequency (RF).

14 2.6

Impact of Electromagnetic Interference by Mobile Phone

Cellular phone is the most common source of impact EMI during ECG acquisition. GSM Cellular telephone will interfere with medical equipment [11].

Most

interference occurred with the device that displays the waveform. However, from the article of “Cellular Telephone Interference with Medical Equipment”, it comes out with the statement recent technological advances have changed the EMI landscape for the better [11]. The article also makes a conclusion cellular telephone can interfere the medical equipment output. The article “Use of Cellular Telephone in the hospital Environment”, come out the statement when the mobile phone is used in a normal condition, there is no interference will occurred with the medical device.

From the another paper of study shows that in area where the incoming signal is strong, the mobile phone will transmit low power level to conserve battery while in area where the incoming signal is weak, the mobile will transmit higher power to ensure reliable communications. The mobile phone alters the power output based on the measured RSSL level. The altering change to the power output of the mobile phone to create a challenging situation for testing the potential interaction. The study is completely come out the statement in area where the incoming signal is strong, the mobile phone can emit minimal power and the impact on the medical devices is minimal too [18 ].

Furthermore, there is a result show that the presence of wireless telecommunication device causes the EMI to medical device [18]. Although many device manufactures have known the Electromagnetic Compatibility (EMC), there still appears to be less awareness of the problem of EMI. There is the need to continue educate the users, manufactures and regulators about the EMI.

The

standard for EMC is very important to preventing the Electromagnetic Interference in the environment.

CHAPTER 3

METHODOLOGY

3.1

Introduction

This chapter discuss the methodology adapted of whole project. In order to obtain the target of the project, all the basic knowledge and information need to be understood. Thus, literature study have to be carry on at the beginning of the project. Then the study is continued by understanding the method and equation on develop a portable ECG circuit and designing the block diagram of LabVIEW. The portable ECG system is use for collecting the data in several place with the help of LabVIEW to display the output. Then, there is an analysis done on the data to determine in which condition of environment have the highest effect of EMI during ECG acquisition. Figure 3.1 shows the block diagram of the project.

ECG CIRCUIT DAQ card LabView

Figure 3.1: Block diagram of the project

16 The ECG signal was taken in different environment such as in the lab, a free space, beside the medical device, near to the phone and in the room. Figure 3.2 shows the overview of the project. The project is divide into two parts that are software and hardware implementation. The detail of each part is discuss in the following sections.

Figure 3.2: Overview of the project

3.2

Implementation of Hardware

In this section, the component that had been use in implementing the hardware of the project and the device that are used is discussed detail. For example USB 6009, ECG system, ECG simulator and amplifier.

17 3.2.1 ECG Simulator

Figure 3.3: ECG 200 Figure 3.3 shows the ECG simulator (ECG 200). It is use to replace ECG signal of the human body. It is a very useful device that can generate same ECG signal as our human. The signal that generated is more consistent and stable. It is free of the noise due to the error of the human body. For example when the user is cold, the musculature contracts, and this contraction will be taken up by the ECG electrode. Hence there is a noise in signal [15]. By having this device, it eases the project to achieve the objective by saving the time to filter the noise from the human body himself.

3.2.2 NI USB 6009 Data Acquisition

NI USB 6009 is use as the medium to connect the analog output of the ECG amplifier and the computer. The analog signal of the ECG signal is connect to the NI USB 6009,

and it convert it to digital signal which can be read from software of

LabVIEW. Then the LabVIEW is used to display out the signal. It has 8 analog inputs, 2 analog output channels, 12 digital input/output channel and 32 bit counter with 42 k/s speed. Figure 3.4 shows the NI USB 6009. The reference voltage for A/D in DAQ card could be chosen. ±5V was set because the analog signal conditioning circuit had amplified the signal enough.

18

Figure 3.4: NI USB 6009 Data Acquisition

Figure 3.5 shows the analog terminal of NI USB 6009 data. There are 16 analog terminals.

19

Figure 3.5: Analog terminal of NI USB 6009 data

Figure 3.6: Analog input circuitry

Figure 3.6 shows the analog input circuitry of USB 6009. The multiplexer (MUX) control the routes of the AI channel. It only routes one AI channel at a time to the Programmable Gain Amplifier (PGA) [16]. PGA provides input gains of 1, 2, 4, 5, 8, 10, 16 or 20. The gain of PGA is automatically calculated based on the voltage range selected in measurement application. On the other hand, the Analog Digital Converter (ADC) digitizes the AI signal by converting the analog signal into a digital code. The USB 6009 able to perform both single and multiple analog and digital conversion of an infinite number of samples [16]. The voltage of all the channels of input mode is limit to ±10 V while the measurement return from the device is +20 V.

Figure 3.7: Analog output Circuitry

20 The USB 6009 consist of two independent AO channels which can generate output in the range of 0 - 5 V. Digital to analog Converter (DAC) is use to convert the digital codes to analog voltages. 3.2.3

ECG Circuit

The main part of ECG system is instrumentation amplifier and filter. However due to the project is using ECG simulator as the ECG signal provider, there filtering part is not include in the project.

J1 V1

V4

13

0

Key = Space

9V

15 R8 10kΩ

9V 4

U2

LED1

2 6

R7 20kΩ

9 R10

Comparator

6

330Ω

3

0 7

0

1

5

UA741CD

8 Left_Arm

7

Left_Arm 1

U3

3

R4

8

6

1

4 R5

10

51Ω

4

2

R3 2 5.6kΩ Right_Arm

4

0

5

INA121U

11 R1 51Ω

5kΩ U1

2

3

Output Output

6 3 7

1

5

Figure 3.8: ECG circuit diagram

UA741CD

Instrumentation amplifier

21

Figure 3.9: ECG circuit Figure 3.8 show the ECG circuit diagram of my project while Figure 3.9 is the circuit that implement in strip board. The front part is the voltage comparator and the second part is the instrumentation amplifier. The detail for voltage comparator and instrumentation amplifier is discussed in the following part.

A)

Comparator J1 V1

V4

13 Key = Space 15 R8 10kΩ

0 9V

9V 7 4

U2

LED1

2 6

R7 20kΩ

9 R10

6

330Ω

3

0 7

0

1

5

UA741CD

4

Figure 3.10: Circuit of voltage comparator Figure 3.10 shows the voltage comparator circuit. Voltage comparator is a device that compares two voltages signal and determines which one is greater. The result of the comparison is indicated by the output voltage. If the op-amp's output is

22 saturated in the positive direction, the non-inverting input (+) is a greater voltage than the inverting input (−), all voltage measured will respect to ground and vice versa. The output is connecting to a LED for indicating the result of comparison. The reference voltage value is set through equation (3.1) [17]:

(

supply

=

)

6V

The reference voltage is set to 6 V. LED will turn ON when the input voltage is greater than 6 V.

The purpose of connecting the ECG circuit with a voltage

comparator is to determine the voltage of battery is always greater than 6 V. Hence it able to provide enough voltage supply to the circuit.

B)

Amplifier

DC restoration amplifier

Instrumentation amplifier V1

V4 8

0 9V

9V R4 51Ω

7 Left_Arm

Left_Arm

V2

0.5mVrms 50 Hz 0°

7

6

U3

4 R3 5.6kΩ 5

8

2

6

1

R1 51Ω

2 5

4

5kΩ U1 Output Output

2

3

4

Right_Arm

R5

1

6 3 7

1

5

INA121U

0

Figure 3.11: Amplifier circuit for ECG signal application

UA741CD

23 ECG signal is in the range of 0.5 to 4 mV. Hence, to overcome the problem, three stage of amplifier need to undergo. The stage of amplifier is shown in Figure 3.10. First stage is buffers amplifier. It is placed in low gain such as 10 V/V. Then, 2nd state is a unity gain differential amplifier. The first stage and 2nd stage are called as instrumentation amplifier. It is compactible in a small chip (INA121). Figure 3.12 shows the instrumentation amplifier circuit which consists of 3 operational amplifiers.

Figure 3.12: Instrumentation amplifier INA121 The voltage gain for 1st and 2nd stage can be calculated through equation (3.2) [5]: (3.2)

9.928 The 3rd stage is a dc restoration amplifier which used in a feedback arrangement to null out the dc offset. It also amplifiers the signal by giving some gain. The gain can be calculated through equation (3.3) [5]: (

)

24 The total gain of the circuit is calculated using equation (3.4): (3.4) = 963

3.3

Implementation of Software

For software implementation, LabVIEW is used to display the output of the ECG circuit.

LabVIEW is a graphical programming environment used to develop

sophisticated measurement, test, and control systems using intuitive graphical icons and wires. It offers unrivaled integration with thousands of hardware devices and provides hundreds of built-in libraries for advanced analysis and data visualization. LabVIEW program has two components which are block diagram and a front panel. When receive the data from serial port, the resource of USB 6009 will use to process and transform the wavelet to find the characteristic points of ECG signal. In the project there is two LabVIEW block diagram, 1st program is used to display and save data while 2nd program is to read the saving files.

Program for calculating the Blood Pressure

Figure 3.13: Block diagram of the 1st program in LabVIEW

25 Figure 3.13 shows the block diagram of the 1st program. It replaced the oscilloscope device. Basically, the block diagram can be understand as physical channel in the front part is use to select which channel’s data of the USB 6009 should be taken. Then, set the value for threshold of the ECG signal and calculating the blood pressure program will run depend to the threshold value that have been set. At the end, there is an “SA E” button use to save all the data in a text file. Figure 3.14 is the front panel of the LabVIEW.

Figure 3.14: Front panel of 1st program in the LabVIEW

26

Figure 3.15 shows the block diagram of 2nd program. It is use to read the file that have been saved and it can read two file in a time. The file is save in text file. Through the block diagram in Figure 3.15, the data that save can be reconstructed back and the ECG signal can be displayed.

Figure 3.15: Block diagram of the 2nd program LabVIEW

27 Front panel of 2nd program is shown in Figure 3.16. From that program, it can read the files that have been save at the 1st program. Moreover, ECG signal can be analysis through the 2nd program. From the panel, we can compare the acquired signal with the reference signal.

Figure 3.16: Front panel of the 2nd program LabVIEW

CHAPTER 4

RESULT AND DISCUSSION

4.1

Introduction

Some experiment has been conduct for the project.

First and foremost, an

experiment is conduct to analysis the effect of the environment to the EMI of ECG signal. Next, data collection is done at each environment to observe the effect of EMI to ECG signal.

4.2

Experiment : Analysis the Effect of Environment to the EMI during ECG Acquisition

An experiment is conducted to determine the effect of environment to the EMI of ECG signal. The procedures and the result are discussed in the following sections. ECG simulator

USB 6009

ECG circuit

Figure 4.1: Experimental with ECG circuit

LabVIEW

29 4.2.1

Procedures

1) The circuit was connected according to Figure 4.1. 2) Voltage of 9 V is supply by using 9V battery. 3) The signal of ECG in different environment is recorded using LaBVIEW and tabulate in Table 4.1. 4) The amplitude of the PQRST is measured and recorded in Table 4.2. 5) A graph of amplitude of PQRST vs. Environment is plotted. 6) Based on the graphs, the result is analyzed.

4.2.2

Experimental Result Analysis

From experiment, the signal is record in Table 4.1 and Table 4.2. A graph of amplitude of PQRS vs. Environment is shown in Figure 4.3.

Table 4.1: Relation between different Environment and ECG signal Environment

1. REFERENCE (Free of EMI)

2. In Room

ECG Signal

30

3. In MEP lab

4. In computer lab

5. Beside Ultrasound

6. Beside Radio

31 Table 4.2: Relation between different phone environment and ECG signal acquired Phone Environment 1. CSL

2. HTC

3. Samsung Galaxy

4. E - Touch

32 5. Sony Ericsson Price > RM500

6. Sony Ericsson Price < RM500

7. Nokia Price > RM500

8. Nokia Price < RM500

33

Figure 4.2: PQRST of signal Figure 4.2 show the point of the PQRST of the ECG signal. Every points have their own specific amplitude.

Table 4.2: Relation between Environment and Amplitude of PQRST

Places REFERENCE ( Free of EMI) Beside Ultrasound

P

Amplitude ( V) Q R

S

T

3.1

2.6

4.3

2.6

3.3

3.1

2.6

4.3

2.6

3.3

Beside Radio

3.1

2.6

4.3

2.6

3.3

MEP lab

3.1

2.6

4.3

2.6

3.3

Room

3.1

2.6

4.3

2.6

3.3

Computer Lab

3.1

2.6

4.3

2.6

3.3

Phone Environments CSL

7.5

2.6

4.3

2.6

7.5

HTC

3.1

2.6

4.3

2.6

3.3

Samsung Galaxy

3.4

2.6

4.3

2.6

3.5

E-touch

3.1

-6.0

4.3

-6.0

3.3

Sony >RM500

3.1

2.6

4.3

2.6

3.3

34

Sony < RM500

3.1

1.0

4.3

1.0

3.3

Nokia > RM500

3.1

2.6

4.3

2.6

3.3

Nokia < RM500

7.0

2.6

4.3

-1.0

6.5

Table 4.2 shows the amplitude of the PQRST of the ECG signal that taken in different environment. The ECG signal that taken on a football field is set as the reference for the experiment. From the figure (shown in the Table 4.1), the ECG signal that taken beside radio and in MEP lab consist of few noise. However, the noise does not affect the ECG data of the patient. This can be proven by the amplitude of the PQRST in Table 4.2. Its amplitude is the same with the reference.

This is the same with the environment consists of more advance phone such as HTC, Samsung Galaxy, Nokia more that RM500 and Sony Ericsson more than RM500. While, in the phone environment consist of CSL, E-Touch, Nokia Phone less than RM500 and Sony Ericsson Phone less than RM500 have generate a lot of EMI to environment. The ECG signal of the above phone environment either in visualization or amplitude of PQRST can clearly show that the signal is full of EMI. The EMI have affected the ECG data, the amplitude of PQRST is run out from the reference value. Hence, there is a conclusion normal environment and more advance phone would not affect the ECG data. Besides, not all phones provide high EMI to environment; it needs to depend to its brand and price. Figure 4.3 shows the graph of amplitude of PQRST vs. environment.

35

10 8 6

Amplitude

4

P

2

Q

0

R S

-2

T

-4 -6 -8

Type of environment

Figure 4.3: Graph amplitude of PQRST vs. Environment

CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1

Conclusion

A portable ECG circuit is implemented. It is design in small, light, compatible and portable. Through the assistance of the ECG simulator and NI USB 6009, the ECG signal can be displayed from the screen laptop. With the help of the hardware, the study of environment based condition of the EMI during ECG signal is done successfully. Different environment give certain effect during ECG acquisition. Mobile phone provides the highest level of EMI to the environment. However, not all mobile phone produce high EMI. The more expensive and advance phone is less producing in EMI. It is proven through the data acquired in the experiment.

5.2

Recommendation

Recently, the development in technology is moving rapidly. However the problem of EMI still occured. Hence, here is some recommendation for future improvement.

Firstly, there is need to design a hardware that can eliminate all the environment interference. For example use the faraday cage during the ECG acquisition.

Secondly, there is need to improve the ECG with more efficiency filter and the last but not the least, there is need to have a good collaboration with other electronic device company to make sure their products are free of interference. The electronic company should not only focus in create new advance product but need to care about the side effect of the device.

38 REFERENCES

1.

Yang, S. and G. Yang (2010). ECG Pattern Recognition Based on Wavelet Transform and BP Neural Network. ISBN 978-952-5726-09-01

2.

Chitore, D., S. F. Rahmatallah, and M. I. Derzi. (2001). Decision logic for diagnostic evaluation of ECG signals. Microprocessors and Microsystems. 12(2): p.92-96.

3.

Sudirman, R., N.A. Zakaria, M. N. Jamaluddin, M. R Mohamed, K. N. Khalid. (2009). Study of Electromagnetic Interference to ECG Using Faraday Shield, ams, pp. 745-750, Third Asia International Conference on Modeling & Simulation.

4.

Argyle: Micro EKG Manual (part of ECG) http://www.madsci.com/manu/ekg_part.htm#TopPage

5.

Carr, J. J. and Brown, J. M. (2000). Introduction to Biomedical Equipment and Technology. 4th Edition. Upper Saddle River, New Jersey Prentice Hall.

6.

Walker, B., A. Khandoker, and J. Black (2010). Low cost ECG monitor for developing countries. ISBN: 978-1-4244-3517-3

7.

Wei, Y. C., Lee, Y. H., and Young, M. S. (2008). A Portable ECG Signal Monitor and Analyzer. The 2nd International Conference on Bioinformatics and Biomedical Engineering, Shanghai, China, pp. 1336–1338.

8.

Ephone International Pte Ltd : EPI LIFE 2009 http://www.epi.co.sg/index.html

9.

National Instruments corporation: Product information, 2010 http://www.ni.com/labview/whatis/

39 10.

Zhang, J., P. Wei, and Y. Li. (2008). A LabVIEW based measure system for pulse wave transit time. ISBN: 978-1-4244-2254-8

11.

Tri JL, Severson RP, Hyberger LK, Hayes DL. (2007). Use of cellular telephones in the hospital environment. Mayo Clinic Proc. 82(3):276-8.

12.

Baranchuk. A, Jaskaran Kang, Cathy Shaw, Debra Campbell, Sebastian Ribas, Wilma M. Hopman (2008). Electromagnetic interference of communication devices on ECG machines. Clinical cardiology, 2009.32(10): p. 588-592.

13.

Van der Togt, R., Van lieshout, E. J., MD Reinout Hensbroek, Binnekade, J. M. (2008). Electromagnetic interference from radio frequency identification inducing potentially hazardous incidents in critical care medical equipment. JAMA. Vol 299(24): p. 2884.

14.

Chong, K. L., David Holden, Tim Olin. (2010). Heart rate monitor: Analogue Electronic ENGN3227

15.

Riemer Meditech. (2010). Interference in the ECG and its elimination. RIEMER MEDITECH GMBH, BLAUSTEIN Herrlingen PH: (702) 3152999

16.

National Instrumentation corperation: Product information, 2010 http://www.ni.com/labview/whati/usb6009/

17.

Floyd, T. L. (2008), Electronic Devices. Eight Editions. Upper Saddle River, New Jersey Prentice Hall

18.

Tan K-S, Hinberg I, Wadhwani J. (2002). Electromagnetic interference in medical devices: Health Canada’s Past and Current Perspective and Activities. pp. 1283 - 1288 vol.2

APPENDIX A

Datasheet and circuit design for hardware

41

INA 121

42

43

44

45

46

47

USB 6009

48

49

50

51

52

53

UA 741

54

55

56

APPENDIX B

Block Diagram design for software

58

59