winsound' for signal acquisition

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International Journal of Advances in Engineering Science and Technology 190

www.sestindia.org/volume-ijaest/ and www.ijaestonline.com ISSN: 2319-1120

ISSN: 2319-1120 /V2N2: 190-195 © IJAEST

Real Time Acquisition and Analysis of ECG signalsusing MATLAB

RAMAN YADAV SHARDA VASHISTH* ASHOK K. SALHAN

EECE Department EECE Department

Biomedical Instrumentation Division

ITM University, Gurgaon ITM University, Gurgaon Defence Institute of Physiology and

Haryana, India Haryana,India Allied Sciences DRDO, Delhi ,India

[email protected] [email protected] [email protected]

* Corresponding Author

Abstract

The purpose of this paper is to design a portable, light weight ECG acquisition circuit for real time

monitoring of ECG of cardiac patients. The signal acquired from the body using acquisition circuit is then

displayed onto the computer using the sound port as a serial interface between circuit and PC. The real

time acquired signal is then analyzed using MATLAB. MATLAB program amplifies and filter the raw

ECG to eliminate noise added to the signal. It can further be used for identifying a number of diseases to

reduce the death rate due to heart diseases.

Keywords: ECG signal acquisition; MATLAB software; Sound Port;

I. INTRODUCTION

Now-a-days, heart diseases are a leading cause of death. According to World Health Organization (WHO)

estimation cardiovascular diseases are the main cause of death, nearly 17 million lives a year [1].

Healthcare for elder people has been the main focus of this proposed research. Electrocardiogram is the

signal of the heart muscles which are recorded from the body surface, to analyze any heart disease. It was

developed by William Einthoven in 1901, for which he was awarded the Nobel Prize in Medicine in 1924

[2]. A typical ECG signal for a normal heart beat is shown in Figure 1. Atria contraction gives the first

upward deflection P, and is known as atrial complex. Due to the action of ventricles, the other deflections

Q, R, S and T are observed and are known as the ventricular complexes [3]. Pressure exerted by heartmuscles in one pumping cycle gives the value of voltage. The voltage created in this process is of about 1

to 3mV. If the heartbeat moves up or down from the normal position then it shows abnormal rhythms

which may be caused due to a heart disease. These pathologic changes can be analyzed by ECG signal.

The changes can also be monitored using a handy ECG monitoring system [4].



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RAMAN YADAV et al.

ISSN: 2319-1120 /V2N2: 190-195 © IJAEST

Figure 1: A typical single ECG signal

Various bio-signals such as ECG, heart beat rate, blood pressure, blood oxygen saturation level, activitysignal such as acceleration and angular velocity are used for healthcare in daily life [5]. Analysis of ECG

is helpful in telemedicine and homecare. It helps in the reduction of relative expenses and hospital waiting

lists. But due to various factors faulty diagnoses may cause a risk to the patient’s health. So it needs a

qualified system and infrastructure with high efficiency [6]. Biomedical signals such as ECG, EMG, EEG

are very important in biomedical engineering and need real time monitoring, so a computer system plays

an important role for the various measurements and tests, with a better performance and lower cost [7].

Holter Monitoring system is non-invasive method which can be used to monitor ambulatory patient. ECG

signal can be acquired from the patient and then analyses and processing is done offline [8]. The acquired

signal is then interfaced with the computer using DAQ card. So needs DAQ card which further increase

the cost of the system and make the arrangement bulky. Most commonly used technique is Wilson

Central Terminal arrangement where ECG signal acquired using 3 electrodes [9]. Another system used is

Implantable Cardioverter Defibrillator (ICD) gives more accurate signal. But it is more expensive so used

only on the patient having high risk [10]. MOLEC monitor system acquires, analyzes, process and detect

abnormalities from the ECG signal in real time but requires analog to digital converter due to which cost

of the system increases [11]. Continuous monitoring of the ECG signal can be done using EPI-MEDIC

system which uses RS-232 port for computer interface [12]. Twelve lead are used to acquire ECG signal

which restricts the mobility of the patient. R –test is non-invasive method which continuously monitors

the signal for large interval of time. But the system is sensitive to interference can be easily corrupted due

to motion artifacts. Data can be transferred using sound card of PC which makes overall arrangement

convenient and effective.

In the present approach, the developed system comprises of electrodes, ECG acquisition circuit, a

computer system using the MATLAB software. The ECG signal acquired from the ECG acquisition

circuit is then fed to the sound port of the PC. The sound card of computer converts the analog signal

received into digital form and also amplifies the signal. MATLAB software [13, 14] program acquires

and filters the signal received from the sound port to remove the noise content added to the signal.



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Real Time Acquisition and Analysis of ECG signals using MATLAB

ISSN: 2319-1120 /V2N2: 190-195 © IJAEST

II. MATERIALS AND METHODS

The analysis of ECG signal mainly involves the detection of QRS complex, P wave and T wave. The

ECG acquisition system consists of electrodes, amplifiers, filters to remove noise, and output display

device (Laptop/PC). The Functional block diagram of a Real time acquisition and transmission of ECG

signal is shown in figure 3.

A. ECG Acquisition

The main objective of the hardware circuit used is to acquire the ECG signal from the body surface. To

achieve this, the hardware acquisition unit is synchronized with MATLAB (matrix laboratory) software

for automatic data storage. The acquired signals are fed to ECG amplifier as these signals are in the range

of 1 to 3 mV so amplification of these weak signals is necessary. Output of the amplifier is then fed to

high pass filter and low pass filter circuit to filter the high and low frequency components and 50 Hz

power line interference from the acquired signal. The desired output from filter is then inputted into the

PC sound port. With the help of MATLAB program we recognize the ECG signal in the sound port of the

PC and then analyze the waveform obtained on the screen.

B. ECG Electrodes

Acquisition of ECG signal can be done with 3 or 6 or 12 electrodes. Here we propose to use 3 electrodes

to acquire ECG signal, two electrodes are placed on left and right wrist to provide positive and negative

connection. Ag/AgCl electrodes are used to pick the bio-potential signal from body surface and then to

convert them into a voltage signal. In AgCl electrodes, the sensors are of silver and coating of chloride

ions reduce skin impedance for perfect current flow [5]. The position of electrodes is set using the

Einthoven’s triangle. Figure 3 shows the diagram of Einthoven’s triangle for placement of electrodes on

body surface.

Figure 3: Einthoven’s Triangle

C. Front-end Amplifier:




RAMAN YADAV et al.

ISSN: 2319-1120 /V2N2: 190-195 © IJAEST

An operational amplifier chip TL084C amplifies the ECG signal picked from the body surface. The OP-

AMP has a common mode rejection ratio (CMRR) of 86 dB and an adjustable gain of 500. Right leg

driven circuit is used to improve the CMRR of the circuit. Filter circuit is used to eliminate the noise

picked in this process. The ECG acquisition circuit uses 9 volts battery to eliminate the use of 230 V

power supply as the 230 V power supply is main source of noise in the circuit and also not safe to use for

measuring the signal.

D. Output Display Unit:

The output of the acquisition circuit is connected to the sound port of the interface unit (PC) and the

signal displayed using the MATLAB software. Sound port of PC provides the interface between the PC

and mobile phone. It makes the system cost effective and convenient, as there is no need of data

acquisition card for the interfacing between circuit and PC. Using a MATLAB program code, the PC can

recognize and display the ECG signal received at the sound port. The command “winsound” in MATLAB

is used to acquire the signal from the sound port and display on the screen. To minimize the noise content

from the real time acquired signal, FIR digital filter and band pass filter with pass band 0.05-150 Hz can

be used.

The subject was asked to sit comfortably on chair. The raw ECG signal was then acquired at normal

position. The signals received are then filtered using digital filters used in MATLAB program.

Figure 3: Functional diagram of ECG acquisition circuit

III. RESULTS AND DISCUSSIONS

Using ECG acquisition circuit we acquire signal at normal position. Figure 4 shows the raw ECG signal

acquired directly from the sound port of the PC and the filtered signal using digital filters in the

MATLAB coding displayed in figure 5. The code developed in MATLAB is capable of acquiring and

filtering raw ECG signal. Here MATLAB 7.5 (Release 2007b) is used for the real time acquisition and

filtering of raw ECG signal acquired. The frequencies of digital filters used are set accordingly to

acquire signal lies in the frequency range of 0.05-100 Hz. Here we are using sound port of the PC for



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Real Time Acquisition and Analysis of ECG signals using MATLAB

ISSN: 2319-1120 /V2N2: 190-195 © IJAEST

interfacing between PC and acquisition circuit so there is no additional requirement of DAQ card.

Effective signals can be acquired with proper selection and placement of electrodes. The Instrumentation

amplifier TL-084C is used to eliminate power line interference. An amplifier used amplifies the noise

signal added into the desired signal which can be minimized using analog filter.

Figure 4 Raw ECG acquired directly using sound port of PC

Figure 5 Filtered signal using digital filter in MATLAB program

IV. CONCLUSION

The rest ECG signal can be acquired easily using a single channel ECG amplifier. Any bio-medical

signals viz. ECG, EMG, EEG can be analyzed using this application software with proper selection of

amplification and filtering ranges. The signal acquired can be interfaced with PC using sound port so

there is no additional requirement of DAQ which makes the system cost effective. The system can be

extended and used with the standard 12 lead system for online diagnosis, analysis and distant monitoringof bio medical signal. The system can be integrated with the wireless communication device like a

mobile phone so that telemonitoring can be made feasible and the data can be analyzed by cardiologist in

real time to reduce the trouble taken by patients to travel long distance. This is left as a future scope.

REFERENCES

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conference of IEEE, EBMS, Minneapolis, Minnesota, USA, pp. 950-953, September 2-6, 2009.




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ISSN: 2319-1120 /V2N2: 190-195 © IJAEST

[2] Tasneem Ibrahim Abdalla,shiemaa Sidahmed, Sharief F.Babiker ”Transmission of Real-Time Clinical

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winsound' for signal acquisition

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