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patient monitoring using surface electromyography

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  • 1. 1 ACKNOWLEDGEMENT I express my sincere thanks to my project guide, Prof. Avinash Tandle of DEPT. of Electronics & Communication for guiding me right from the inception till the successful completion of the project. I sincerely acknowledge him for extending their valuable guidance, support for literature, critical review of project and the report and above all the moral support he had provided to me with all stages of this project. My thanks are due to all those who have directly or indirectly helped me in preparing this project report. However, I accept the sole responsibility for any possible error of omission and would be extremely grateful to the readers of this project report if they bring such mistakes to my notice.
  • 2. 2 Index Index................................................................................................................................... 2 List of figures...................................................................................................................... 4 List of tables........................................................................................................................ 6 Abstract.............................................................................................................................. 7 1. Introduction ................................................................................................................... 8 1.1 Problem statement ................................................................................................ 8 1.2 Project Survey........................................................................................................ 9 1.3 Project Selection.................................................................................................... 9 1.4 Definition of Wireless Biotelemetry..................................................................... 9 1.5 History of Biotelemetry........................................................................................ 11 1.7.1 Obstetrical Telemetry System.................................................................... 14 1.7.2 Telemetry in Operating Rooms.................................................................. 15 1.7.3 Sports Physiology Studies through Telemetry ........................................ 15 1.8 Working Principle................................................................................................. 17 1.8.1 Frequency Modulation................................................................................. 20 1.8.2 Pulse Width Modulation .............................................................................. 20 1.9 Implantable units.................................................................................................. 21 1.10 Advantages ........................................................................................................ 22 1.11 Disadvantages ................................................................................................... 22 2.0 Electromyography.................................................................................................... 23 2.1 Definition of EMG ................................................................................................ 23 2.1.1 Wide spread use of EMG............................................................................ 23 2.2 Signal origin:......................................................................................................... 24 2.3 Excitability of muscle membranes .................................................................... 25 2.4 Generation of EMG signal.................................................................................. 25 2.6 composition of EMG signal ................................................................................ 28 2.7 Nature of the EMG signal................................................................................... 30 2.8 Factors influencing the EMG signal.................................................................. 31 2.9 Physiology of EMG.............................................................................................. 32 2.9.1 Electrodes...................................................................................................... 33 2.9.2 EMG Electrode Placement ......................................................................... 36 2.9.3 Amplifier of EMG signals............................................................................. 38 2.10 Definition of Pulse (Heartbeat) rate:............................................................... 40 2.10.1 Physiology................................................................................................... 41 2.10.2 Normal Pulse Rates:.................................................................................. 42 3.0 Taxonomy of wireless medical systems .............................................................. 43 3.1 Radio Frequency ................................................................................................. 43 4.0 System design.......................................................................................................... 48 4.3 Instrumentation Amplifier.................................................................................... 49 4.3.1 Low pass filter:.............................................................................................. 49 4.3.2 High pass filter:............................................................................................. 51 4.4 Pulse monitoring system .................................................................................... 52 4.5 design description................................................................................................ 52 4.6 Transmitter circuit diagram ........................................................................... 55 4.7 Receiver circuit diagram:............................................................................... 56
  • 3. 3 5.0 Programmer description for system...................................................................... 57 5.1 Observed signals................................................................................................. 59 5.2 Flowchart............................................................................................................... 61 5.2.1 TX section flowchart..................................................................................... 61 5.3 Pulse rate result................................................................................................... 63 5.4 Emg result............................................................................................................. 65 5.5 result Suggestions for further advancements ................................................. 68 5.6 Application area of project.................................................................................. 68 Conclusion & Future work............................................................................................. 70 References...................................................................................................................... 71 Appendix.......................................................................................................................... 72
  • 4. 4 List of figures Figure 1 ECG measurement using immersion electrodes. Original Cambridge electrocardiograph (1912) built for Sir Thomas Lewis. ............................................ 12 Figure 2: Telemetry receiving system for monitoring foetal heart rate and urine contractions in use......................................................................................................... 15 Figure 3: A three channel telemetry system to monitor the physiological data of a sprinter............................................................................................................................. 17 Figure 4: Transmitter circuit.......................................................................................... 18 Figure 5: Receiver Circuit ............................................................................................. 18 Figure 6: Biotelemetry mobile unit............................................................................... 19 Figure 7: Pulse Width Modulation................................................................................ 20 Figure 8: Implantable units ........................................................................................... 21 Figure 9 Basmajian & DeLuca: Definition Muscles Alive Unlike the classical...... 23 Figure 10 : Application areas of kinesiological EMG................................................ 24 Figure 11 Motor unit. Adopted & modified.................................................................. 24 Figure 12 Schematic illustration of depolarization/ Repolarization cycle .............. 25 Figure 13 The Action Potential. Adopted & redrawn ................................................ 26 Figure 14 The depolarization zone on muscle fiber membranes. Adopted & modified2.5 signal propagation and detection........................................................... 26 Figure 15 The model of a wandering electrical dipole on muscle fiber membranes. Adopted & modified ................................................................................ 27 Figure 16 Generation of the triphasic motor unit action potential. Adopted & modified ........................................................................................................................... 28 Figure 17 Superposition of MUAPs to a resulting electromyogram Adopted & modified ........................................................................................................................... 28 Figure 18 Recruitment and firing frequency of motor units modulates force output and is reflected in the superposed EMG signal Adopted & modified..................... 29 Figure 19 The raw EMG recording of 3 contractions bursts. .................................. 30 Figure 20 The influence of varying thickness of tissue layers below the electrodes: Given the same amount of muscle electricity condition 1 produces more EMG magnitude due to smaller distance between muscle and electrodes 31 Figure 21 Raw EMG recording with heavy ECG....................................................... 32 Figure 22 Frequency Spectrum of the EMG signal ................................................. 33 Figure 23 Surface EMG electrodes............................................................................. 34 Figure 24 Ground electrode for surface EMG .......................................................... 34 Figure 25 The preferred electrode location is between the motor point and the tedious insertion ............................................................................................................. 36 Figure 26 A schematic of the differential amplifier configuration............................ 39 Figure 27 pulse rate basic ............................................................................................ 42 Figure 28 Bluetooth Protocol Stack............................................................................. 45 Figure 29 ZigBee Protocol Stack................................................................................. 47 Figure 30 Block diagram ............................................................................................... 48 Figure 31 Burr brown amplifier..................................................................................... 48 Figure 32 Burr brown using INA 128........................................................................... 49 Figure 33 2nd order LPF............................................................................................... 49
  • 5. 5 Figure 34 Low pass Filter design................................................................................. 50 Figure 35 Burr brown HPF............................................................................................ 51 Figure 36 High pass filter design ................................................................................. 51 Figure 37 Pulse monitoring system............................................................................. 52 Figure 38 Transmitter circuit diagram .............................................................................. 55 Figure 39 Receiver circuit diagram.............................................................................. 56 Figure 40 keil software .................................................................................................. 57 Figure 41 X-CTU ............................................................................................................ 58 Figure 42 Filter pro......................................................................................................... 58 Figure 43 Put the finger .................................................................................................... 63 Figure 44Observe the TX pulse........................................................................................ 63 Figure 45 Observe the RX pulse....................................................................................... 64 Figure 46 Lcd display ....................................................................................................... 64 Figure 47 Place the electrode............................................................................................ 65 Figure 48 Push the muscle fiber........................................................................................ 65 Figure 49 Observe the RX pulse....................................................................................... 66 Figure 50 Observe the pulse on LCD ............................................................................... 66 Figure 51 Reception of alert message............................................................................... 67 Figure 52 Read the message ............................................................................................. 67
  • 6. 6 List of tables Table 1 Wireless technologies characteristic graph ................................................. 43 Table 2 ZigBee Uperhand............................................................................................. 47 Table 3 Instrumentation amplifier comparison .......................................................... 52 Table 4 Quad selection comparison............................................................................ 52 Table 5 Wireless device selection ............................................................................... 53 Table 6 Electrode Selection.......................................................................................... 53 Table 7 Microcontroller Selection ................................................................................ 54 Table 8 Comparator Selection ..................................................................................... 54
  • 7. 7 Abstract With miniaturization and technical advancements in electronics and communications field, we are now in a position to safely monitor, diagnose and treat various intricate ailments in patients with relative ease. This has made complex surgeries simple, easy and efficient. Wireless communications have enabled development of monitoring devices that can be made available for general use by individuals/patients and caregivers. New methods for short-range wireless communications not encumbered by radio spectrum restrictions (e.g., ultra-wideband) will enable applications of wireless monitoring without interference in ambulatory subjects, in home care, and in hospitals. Wireless biomonitoring, first used in human beings for featal heart-rate monitoring has now become a technology for remote sensing of patients' activity, blood pulse pressure, oxygen saturation, internal pressures, orthopedic device loading, and gastrointestinal endoscopy. Biotelemetry provides a wireless link between the subject and the remote site where the recording, signal processing, and displaying functions are performed. Rather than using a traditional radio transceiver, which can only broadcast over a limited range, now-a-days the readily available cell phones are used to transmit biological data by creating a link between the subject and a computer receiving the signal via a landline phone. Wireless telemetry of bioelectric signals, specifically neural recordings, is desirable in many research and clinical applications. These include, but are not limited to telemetry and recording of neural activity in laboratory animals, telemetry of EEG, telemetry of short-term implanted electrode arrays for epilepsy medical diagnosis, functional electrical stimulation (FES) systems, and implantable neuroprosthetic devices for sensory and command control. This study will focus on Wireless telemetry in general and also details of Wireless biotelemetry.
  • 8. 8 1. Introduction 1.1 Problem statement The main goal of this project was to design and implement a wirelessly transmitted activity monitor. This device was to record heart rate as well as blood pressure. This data would be used to determine a person’s physical capabilities using a “job match” method. This method would then analyze a person’s heart rate and blood pressure during different physical activities to determine whether or not they are capable of performing the duties required of an occupation. As a person increases in age, their heart may not be able to support the same physical activities it could when he or she were younger. The primary users of this device, occupational therapists, will check the measurements against a reference to determine the candidate’s suitability for the position. It can also be used to evaluate recovery from injury, or even the validity of claims of on-site injuries in the workplace. This method and device would result in an entirely new approach to workman’s compensation, and drastically cut down on false claims. Given the wireless nature of the device and its capability to interface with the majority of PC’s on the market, networking it to a hospital or EMT service for high-risk patients in the home is also an added benefit. There are many people who suffer from heart diseases and high blood pressure. There have been multiple cases where one of these individuals has a heart attack and no one can get to them fast enough to resuscitate them. The wireless activity monitor, in part, is designed to give these individuals a better chance of survival by monitoring their heart rate and blood pressure and transmitting the data wirelessly to a local computer. If a person’s heart rate or blood pressure shows abnormal activity a hospital can be notified immediately over the Internet and a paramedic can be dispatched to the person’s house. Being a light weight package and oriented on the body in a way as to not interfere with job tasks, daily activities, or test procedures, this will become a highly valuable evaluation tool when dealing with physical activity. The design goals for this project were to acquire heart rate and blood pressure readings from a wrist mounted cuff, transmit those readings wirelessly to a local computer, access those readings remotely over a network using a different computer, and display those readings in an intuitive display.
  • 9. 9 1.2 Project Survey Our academic final sem. Engineering purpose for our project team survey many different type of unique and intelligent working project survey some industrial visit, books, and internet Medias. We survey some project as described below. 1. Blood analysis system. 2. Wi-Fi Speech Analyzer. 3. Endoscopy Robot. 4. GSM Security Device. All above project survey we decide that all are very expensive and some material are not available in local market and also require lot of time and heavy R & D hence, we avoid to make it.[1] 1.3 Project Selection Wireless Biotelemetry system is very useful in medical critical I.C.U. For patient and doctor also because this project through any time pulse variation position mobile through under observation continuity between patient and doctor. This technology GSM based satellite communication link then doctor handling patient around the world. Wireless Biotelemetry system project selection for next main advantage all component available in local market, affordable project cost and technical support easily available in college books and websites.[1] 1.4 Definition of Wireless Biotelemetry Biotelemetry is defined as a means of transmitting biomedical or physiological data from a remote location (e.g., astronauts in space) to a location that has the capability to interpret the data and affect decision making (e.g. ground controllers at Mission Control Center). Biotelemetry is a vital constituent in the field of medical sciences. It entails remote measurement of biological parameters. Mode of transmission of physiological data from point of generation to the point of reception can take many forms. Use of wires to transmit data may be eliminated by wireless technology. Biotelemetry, using wireless diagnosis, can monitor electronically the symptoms and movements of patients. This development has opened up avenues for medical diagnosis and treatment. It enables monitoring of activity levels in patients suffering from heart trouble, asthma, pain, Alzheimer’s disease, mood disorders, cardiovascular problems, accidents, etc.
  • 10. 10 A patient’s response and reaction to drugs can be investigated for treatment. Radio-telemetry transmits biological data using various radio transmission techniques. No wires are required to be attached to the patient’s body. The patient just carries a bracelet-sized transmitter that enables monitoring of the patient’s symptoms. Literally, biotelemetry is the measurement of biological parameters over a distance. The means of transmitting the data from the point of generation to the point of reception can take many forms. Perhaps the simplest application of the principle of biotelemetry is the stethoscope, whereby heartbeats are amplified acoustically and transmitted through a hollow tube system to be picked up by the ear of the physician for interpretation. A major advantage of modern telemetry is the elimination of the use of wires. The use of telemetry methods for sending signals from a living organism over some distance to a receiver. Usually, biotelemetry is used for gathering data about the physiology, behavior, or location of the organism. Generally, the signals are carried by radio, light, or sound waves. Consequently, biotelemetry implies the absence of wires between the subject and receiver. Generally, biotelemetry techniques are necessary in situations when wires running from a subject to a recorder would inhibit the subject's activity; when the proximity of an investigator to a subject might alter the subject's behavior; and when the movements of the subject and the duration of the monitoring make it impractical for the investigator to remain within sight of the subject. Biotelemetry is widely used in medical fields to monitor patients and research subjects, and now even to operate devices such as drug delivery systems and prosthetics. Sensors and transmitters placed on or implanted in animals are used to study physiology and behavior in the laboratory and to study the movements, behavior, and physiology of wildlife species in their natural environments. Biotelemetry is an important technique for biomedical research and clinical medicine. Perhaps cardiovascular research and treatment have benefited the most from biotelemetry. Heart rate, blood flow, and blood pressure can be measured in ambulatory subjects and transmitted to a remote receiver-recorder. Telemetry also has been used to obtain data about local oxygen pressure on the surface of organs (for example, liver and myocardium) and for studies of capillary exchange (that is, oxygen supply and discharge). Biomedical research with telemetry includes measuring cardiovascular performance during the weightlessness of space flight and portable monitoring of radioactive indicators as they are dispersed through the body by the blood vessels.
  • 11. 11 Telemetry has been applied widely to animal research, for example, to record electroencephalograms, heart rates, heart muscle contractions, and respiration, even from sleeping mammals and birds. Telemetry and video recording have been combined in research of the relationships between neural and cardiac activity and behavior. There are usually two concerns associated with the use of biotelemetry: the distance over which the signal can be received, and the size of the transmitter package. Often, both of these concerns depend on the power source for the transmitter. Integrated circuits and surface mount technology allow production of very small electronic circuitry in transmitters, making batteries the largest part of the transmitter package.[1] 1.5 History of Biotelemetry[5] In the early days of human space flight, NASA utilized biotelemetry to provide biomedical data from orbiting astronauts to medical personnel at the NASA Johnson Space Center (Manned Space Flight center in the early 1960's). Biomedical data transmitted to Earth from space included astronaut's heart rate, body temperature, ECG, oxygen (O2) and carbon dioxide (CO2) concentration. Further research and technology from NASA was instrumental in driving both telemetry and telemedicine into civil health care. Distance medicine has been around for most of this century. In the early days, doctors treated patients in remote locations via wireless radio and by sending diagnostic samples through the mail. Today, communication is done digitally, and it's called biotelemetry. On an extended space flight, the need to consult, diagnose and deliver effective medical care when the doctor is far away from the patients is crucial. Scientists are developing hardware and software to facilitate this process. Whether it's a case of analyzing blood samples for medical diagnosis when a problem occurs during a three year voyage to Mars or installing a microchip inside the body to measure vital signs, biotelemetry is revolutionizing medical care in space. Historically, Linthoven, the originator of the electrocardiogram, as a means of analysis of the electrical activity of the heart, transmitted electrocardiograms from a hospital to his laboratory many miles away as early s 1903. The rather crude immersion electrodes were connected to a remote galvanometer directly by telephone lines. The telephone lines in this instance were merely used as conductors for the current produced by the biopotentials.
  • 12. 12 Figure 1 ECG measurement using immersion electrodes. Original Cambridge electrocardiograph (1912) built for Sir Thomas Lewis. 1.6 Physiological and Technology Parameters[5] Any quantity that can be measured in the biomedical field is adaptable to biotelemetry. The measurements are divided into two categories: bioelectrical and physiological variables. Bioelectrical variables include measurements like ECG, EMG, and EEG. Signals are obtained directly in the electric form. Physiological variables such as temperature, blood pressure, blood flow, etc require some excitation or external electrical parameters. Transducers are used for the conversion of physiological parameters into an electrical signal. Parameters are measured as the variations of resistance, capacitance, or inductance. Variations can be calibrated to represent pressure, temperature, or blood flow. Base signal is modulated for transmission. And finally, this signal is detected (demodulated) and converted back to its original form. PCM technology offers significant advantages in the application of telemetry to medical and physiological studies. The requirements for less complicated handling, standardized system layout, improvement of weight, size and power supply by commercial battery modules, as well as different wireless data links are met better by a PCM encoder which was specially developed for physiological applications. The advantages of PCM are illustrated by relating the experimental requirements to technical specifications for the elements of a telemetry link.
  • 13. 13 1. Temperature by rectal or oral thermistor. 2. Respiration by impedance pneumograph. 3. Electrocardiograms by surface electrodes. 4. Indirect blood pressure by contact microphone and cuff. As the technology progressed, it became apparent that literally any quantity that could be measured was adaptable to biotelemetry. Just as with hardwire systems, measurements can be applied to two categories: 1. Bioelectrical variables, such as ECG, EMG, and EEG. 2. Physiological variables that require transducers, such as blood pressure, gastrointestinal pressure, blood flow, and temperatures. With the first category, a signal is obtained directly in electrical form, whereas the second category requires a type of excitation, for the physiological parameters are eventually measured as variations of resistance, inductance, or capacitance. The differential signals obtained from these variations can be calibrated to represent pressure, flow, temperature, and so on, since some physical relationships exist. In a typical system, the appropriate analog signal (voltage, current, etc.) is converted into a form or code capable of being transmitted. Currently, the most widespread use of biotelemetry for bioelectric potential is in the transmission of the electrocardiogram. One example of ECG telemetry is the transmission of electrocardiograms from an ambulance or site of an emergency to a hospital. Telemetry is also being used for transmission of the electroencephalogram. Most applications have been involved with experimental animals for research purposes. Telemetry of EEG signals has also been used in studies of mentally disturbed children. The third type of bioelectric signal that can be telemetered is the electromyogram. Telemetry can also be used in transmitting stimulus signals to a patient or subject. For example, it is well known that an electrical impulse can trigger the firing of nerves. Another example is the use of telemetry in the treatment of dropfoot, which is one of the most common disabilities resulting from stroke. A method for correcting dropfoot by transmitting a signal implanted electronic stimulator has been used successfully at Rancho Los Amigos Hospital in Los Angeles. 1.7 Application of the system There are many instances in which it is necessary to monitor physiological events from a distance. Typical applications include the following: 1. Radio-frequency transmissions for monitoring astronauts in space.
  • 14. 14 2. Patient monitoring where freedom of movement is desired, such as in obtaining an exercise electrocardiogram. In this instance, the requirement of trailing wires is both cumbersome and dangerous. 3. Patient monitoring in an ambulance and in other locations away from the hospital. 4. Collection of medical data from a home or office. 5. Research on unrestrained, un-anesthetized animals in their natural habitat. 6. Use of telephone links for transmission of electrocardiograms or other medical data. 7. Special internal techniques, such as tracing acidity or pressure through the gastrointestinal tract. 8. Isolation of an electrically susceptible patient from power-line operated ECG equipment to protect him from accidental shock. These applications have indicated the need for systems that can adapt existing methods of measuring physiological variables to a method of transmission of resulting data. This is the branch of biomedical instrumentation known as biomedical telemetry or biotelemetry. 1.7.1 Obstetrical Telemetry System There has been a great deal of interest to provide greater freedom of movement to patients during labour while the patient is continuously monitored through a wireless link. Thus, from a central location, it is possible to maintain a continuous surveillance of cardiotocogram records for several ambulatory patients. In the delivery room, telemetry reduces the encumbering instrumentation, cables at the bedside. Moreover, when an emergency occurs, there is no loss of monitoring in the vital minutes during patient transfer. The patient carries a small pocket-sized transmitter which is designed to pick up signals for foetal heart rate and uterine activity. The foetal heart rate is derived from Foetal ECG which is obtained via a scalp electrode attached to the foetus after the mother’s membranes are ruptured. Uterine activity is measured via an intra-uterine pressure transducer. If only foetal ECG is measured, the patient herself can indicate uterine activity or foetal movement by using a handheld pushbutton. The receiver located away from the patient, is connected to a conventional cardiotocograph. If the patient exceeds the effective transmission range or the electrode has a poor contact, it is appropriately transmitted for corrective action.
  • 15. 15 Figure 2: Telemetry receiving system for monitoring foetal heart rate and urine contractions in use. 1.7.2 Telemetry in Operating Rooms The use of telemetry in operating rooms seems to be particularly attractive as it offers a means of achieving a high degree of patient safety from electric shock as well as elimination of the hanging inter-connecting patient leads which are necessary in direct wired equipment. Normally there are several parameters which are of interest in surgical patient monitoring, most common being ECG, blood pressure, peripheral pulse and EEG. Basically, the signal encoding is based upon frequency modulation of 4 subcarriers centered at 2.2, 3.5, 5.0 and 7.5 kHz, respectively. The system is designed to give a bandwidth of dc to 100 Hz at the 3 dB point and the discriminator provides 1.0 V dc output for a 10% shift.. The transmitted signals are tuned by a FM tuner whose output is fed into a fourth-channel discriminator which separates the sub- carriers through filtering and demodulates each using a phase-locked loop. The demodulated signals are displayed on an oscilloscope. 1.7.3 Sports Physiology Studies through Telemetry Monitoring of pulmonary ventilation, heart rate and respiration rate is necessary for a study of energy expenditure during physical work, particularly for sports such as squash, handball, tennis and track, etc. The transmitter uses pulse
  • 16. 16 duration modulation, i.e., each channel is sampled sequentially and a pulse is generated, the width of which is proportional to the amplitude of the corresponding signal. At the end of a frame, a synchronization gap is inserted to ensure that the receiving system locks correctly onto the signal. Each channel is sampled 200 times a second. With each clock pulse, the counter advances one step, making the gates to open sequentially. At the opening of a particular gate, the corresponding physiological signal gets through to a comparator where it is compared with the ramp. As soon as the ramp voltage exceeds the signal voltage, the comparator changes state. Thus, the time required for the comparator to change state would depend upon the amplitude of the signal. The counter and gates serve as multiplexer.[5]
  • 17. 17 Figure 3: A three channel telemetry system to monitor the physiological data of a sprinter. 1.8 Working Principle[5] To illustrate the basic principles involved in telemetry, a simple system is described. The stages of a typical biotelemetry system can be broken down into functional blocks, as shown in the Fig for transmitter and for the receiver. Physiological signals are obtained from the subject by means of appropriate transducers. The signal is then passed through a stage of amplification and
  • 18. 18 processing circuits that include generation of a sub carrier and a modulation stage for transmission. Figure 4: Transmitter circuit The receiver consists of a tuner to select the transmitting frequency, a demodulator to separate the signal from the carrier wave, and a means of displaying or recording the signal. Figure 5: Receiver Circuit It receives the multiplexed RF carrier emitted by the patient’s transmitter, as shown in Fig. The tuner has a tuning circuit. When the circuit is tuned to receive signals, the appropriate signal is selected and the unwanted signals are rejected. The multiplexed RF carrier is demodulated to recover the individual sub-carriers. Sub-carriers are then demodulated to reproduce original physiological signals
  • 19. 19 emitted by the patient.A recorder records physiological signals for future reference. Signals can be stored on any secondary media like tape, magnetic discs etc. Display system used can be CRT or computer monitor, chart etc. The modulation systems used in wireless telemetry for transmitting biomedical signals makes use of two modulators .This means that a comparatively lower freq. subcarrier is employed in addition to the VHF which finally transmits the signal from the transmitter. The principle of double modulation gives better interference free performance in transmission and reception of low frequency biological signals. The sub-modulator can be a FM (freq modulation) system or PWM (Pulse Width modulation) system, whereas the final modulator is practically always FM system. Figure 6: Biotelemetry mobile unit If several physiological signals are to be transmitted simultaneously, each signal is placed on a subcarrier of a different frequency and all subcarriers are combined to simultaneously modulate the RF carrier. This process of transmitting many channels of data on a single RF carrier, called frequency multiplexing, is more efficient. The subcarrier is modulated either by AM (amplitude modulation) or FM (frequency modulation). For reducing noise interference, FM is frequently used. The method of modulating sub-carrier, followed by modulating the RF carrier, is termed as AM/FM or FM/FM depending sub-carriers are frequency-
  • 20. 20 modulated and the 1W carrier amplitude modulated, the method is designated as FM / AM. If both the subcarriers and the RF carrier are frequency-modulated, it is designated as FM / FM. 1.8.1 Frequency Modulation In freq modulation, intelligence is transmitted by varying the instantaneous freq in accordance with the signal to be modulated on the wave, while keeping the amplitude of the carrier wave constant. The rate at which the instantaneous freq varies is the modulating frequency. The magnitude to which the carrier frequency varies away from the center freq is called .Freq Deviation. and is proportional to the amplitude of the modulating signal. Usually, an FM signal is produced by controlling the freq of an oscillator by the Amplitude of the modulating voltage. For example The frequency of oscillation in most oscillators depends on a particular value of capacitance. If the modulation signal can be applied in such a way that it changes value of capacitance, frequency of oscillation will change in accordance with the amplitude of the modulating signal. 1.8.2 Pulse Width Modulation Pulse width modulation method offers the advantage that it is less perceptive to distortion and noise. In practice the negative edge of the square wave is varied in rhythm with the ECG signal. Therefore, only this edge contains information of interest. The ratio P : Q represents the momentary amplitude of the ECG. Pulses generated by astable multivibrator (symmetrical 1000Hz) The amplitude or even the frequency variation of the the P: Q ratio and consequently on the ECG signal. The signal output from this modulator is fed to a normal speech transmitter, usually via an attenuator, to make it suitable to the input level of the transmitter. Figure 7: Pulse Width Modulation Modulation schemes are used depending not only on the noise interference, but also on size of the unit, its complexity, location, and other operational aspects.
  • 21. 21 The receiver circuit uses RF tuner to select the transmitted frequency of the base station. The signal is demodulated though demodulator and sent to the processor. The processor enables necessary action depending on the command given to it from the base station. Both transmitter and receiver circuits function as a modem. Control feedback incorporates a control system to enable automatic control of the stimulus, the transducers, or any other part of the instrument system. Tins system comprises a loop in which output from the signal conditioning equipment or signal received is used to control the operation of the system. 1.9 Implantable units Figure 8: Implantable units It was mentioned previously that sometimes it is desirable to implant the telemetry transmitter or receiver subcutaneously. The implanted transmitter is especially useful in animal studies, where the equipment must be protected from the animal. The implanted receiver has been used with patients for stimulation of
  • 22. 22 nerves. The life of the unit depends on how long the battery can supply the necessary current. A partial implant is a good example of a system used for the monitoring of the electroencephalogram where the electrodes have been implanted into the brain and the telemetry unit is implanted within and on top of the skull. This type of unit needs a protective helmet. The use of implantable units also restricts the distance of transmission of the signal. The body fluids and the skin greatly attenuate the signal and because the unit must be small to be implanted, therefore has little power, the range of signal is quite restricted, often to just a few feet. This disadvantage has been overcome by picking up the signal with a nearby antenna and retransmitting it. However, with the plastic potting compounds and plastic materials available today, encapsulation is easily possible. Silicon encapsulation is commonly used. Mercury and silver-oxide primary batteries have been used extensively and, more recently, lithium batteries have found many applications. For field work with free roaming animals, the power requirements are quite different from those needed in a closed laboratory cage. Requirements range from an electrical capacity of 20 mA-hr to 1000 mA-hr. 1.10 Advantages 1. Reduction of the impediment of the information source (patient, subject or animal). 2. Reduction of the psychological effects on the information source. 3. Reduction of measuring artifacts, 4. Reduction of the risk for electroshock, 5. Reduction of the complexity of monitoring of physiological variables, as well as a potential reduction of the total cost of patient care. 6. Totally battery operated instrument so not risk of electrical shutdown. 7. Compact size and light weight. 8. Reliable and repairable product. 1.11 Disadvantages Limitations the system has inherent limitations. Movement of the patient is restricted. If the patient goes beyond the range of the system, his ECG cannot be monitored. Research is in progress for upgrades. Practical systems are being developed to build on existing technology and public infrastructure.
  • 23. 23 2.0 Electromyography 2.1 Definition of EMG[1] "Electromyography (EMG) is an experimental technique concerned with the development, recording and analysis of myoelectric signals. Myoelectric signals are formed by physiological variations in the state of muscle fiber membranes." Figure 9 Basmajian & DeLuca: Definition Muscles Alive Unlike the classical Neurological EMG, where an artificial muscle response due to external electrical stimulation is analyzed in static conditions, the focus of Kinesiological EMG can be described as the study of the neuromuscular activation of muscles within postural tasks, functional movements, work conditions and treatment/training regimes. 2.1.1 Wide spread use of EMG Besides basic physiological and biomechanical studies, kinesiological EMG is established as an evaluation tool for applied research, physiotherapy/rehabilitation, sports training and interactions of the human body to industrial products and work conditions: Typical benefits of EMG The use of EMG starts with the basic question: “What are the muscles doing?” Typical benefits are: 1. EMG allows to directly “look” into the muscle 2. It allows measurement of muscular performance 3. Helps in decision making both before/after surgery 4. Documents treatment and training regimes 5. Helps patients to “find” and train their muscles 6. Allows analysis to improve sports activities 7. Detects muscle response in ergonomic studies
  • 24. 24 Figure 10 : Application areas of kinesiological EMG 2.2 Signal origin: The Motor Unit The smallest functional unit to describe the neural control of the muscular contraction process is called a Motor Unit (Figure 11). It is defined as “...the cell body and dendrites of a motor neuron, the multiple branches of its axon, and the muscle fibers that innervates it . The term units outlines the behavior, that all muscle fibers of a given motor unit act “as one” within the innervation process. Figure 11 Motor unit. Adopted & modified
  • 25. 25 2.3 Excitability of muscle membranes[6] The excitability of muscle fibers through neural control represents a major factor in muscle physiology. This phenomenon can be explained by a model of a semi- permeable membrane describing the electrical properties of the sarcolemna. An ionic equilibrium between the inner and outer spaces of a muscle cell forms a resting potential at the muscle fiber membrane (approximately -80 to -90 mV when not contracted). This difference in potential which is maintained by physiological processes (ion pump) results in a negative intracellular charge compared to the external surface. The activation of an alpha-motor anterior horn cell (induced by the central nervous system or reflex) results in the conduction of the excitation along the motor nerve. After the release of transmitter substances at the motor endplates, an endplate potential is formed at the muscle fiber innervated by this motor unit. The diffusion characteristics of the muscle fiber membrane are briefly modified and Na+ ions flow in. This causes a membrane Depolarization which is immediately restored by backward exchange of ions within the active ion pump mechanism, the Repolarization. Figure 12 Schematic illustration of depolarization/ Repolarization cycle 2.4 Generation of EMG signal The Action Potential If a certain threshold level is exceeded within the Na+ influx, the depolarization of the membrane causes an Action potential to quickly change from – 80 mV up to + 30 mV (Fig. 13). It is a monopolar electrical burst that is immediately restored by the Repolarization phase and followed by an After Hyperpolarization period of the membrane. Starting from the motor end plates, the action potential spreads along the muscle fiber in both directions and inside the muscle fiber through a tubular system. This excitation leads to the release of calcium ions in the intra-cellular space. Linked chemical processes (Electro-mechanical coupling) finally produce a shortening of the contractile elements of the muscle cell. This model linking
  • 26. 26 excitation and contraction represents a highly correlated relationship (although weak excitations can exist that do not result in contraction). From a practical point of view, one can assume that in a healthy muscle any form of muscle contraction is accompanied by the described mechanisms. Figure 13 The Action Potential. Adopted & redrawn The EMG - signal is based upon action potentials at the muscle fiber membrane resulting from depolarization and repolarization processes as described above. The extent of this Depolarization zone (Fig. 13) is described in the literature as approximately 1-3mm² (11). After initial excitation this zone travels along the muscle fiber at a velocity of 2-6m/s and passes the electrode side. Figure 14 The depolarization zone on muscle fiber membranes. Adopted & modified2.5 signal propagation and detection
  • 27. 27 An electrical model for the motor action potential The depolarization – repolarization cycle forms a depolarization wave or electrical dipole which travels along the surface of a muscle fiber. Typically bipolar electrode configurations and a differential amplification are used for kinesiological EMG measures. For simplicity, in a first step, only the detection of a single muscle fiber is illustrated in the following scheme. Depending on the spatial distance between electrodes 1 and 2 the dipole forms a potential difference between the electrodes. Figure 15 The model of a wandering electrical dipole on muscle fiber membranes. Adopted & modified In the example illustrated in figure 15, at time point T1 the action potential is generated and travels towards the electrode pair. An increasing potential difference is measured between the electrodes which is highest at position T2. If the dipole reaches an equal distance between the electrodes the potential difference passes the zero line and becomes highest at position T4, which means the shortest distance to electrode 2. This model explains why the monopolar action potential creates a bipolar signal within the differential amplification process. Because a motor unit consists of many muscle fibers, the electrode pair “sees” the magnitude of all innervated fibers within this motor unit - depending on their spatial distance and resolution. Typically, they sum up to a triphasic Motor unit action potential (“MUAP” - 2), which differs in form and size depending on the geometrical fiber orientation in ratio to the electrode site (Fig. 16):
  • 28. 28 Figure 16 Generation of the triphasic motor unit action potential. Adopted & modified 2.6 composition of EMG signal Superposition of MUAPs Within kinesiological studies the motor unit action potentials of all active motor units detectable under the electrode site are electrically superposed (Fig. 17) and observed as a bipolar signal with symmetric distribution of positive and negative amplitudes (mean value equals to zero). It is called an Interference pattern. Figure 17 Superposition of MUAPs to a resulting electromyogram Adopted & modified
  • 29. 29 Recruitment and Firing Frequency The two most important mechanisms influencing the magnitude and density of the observed signal are the Recruitment of MUAPs and their Firing Frequency. These are the main control strategies to adjust the contraction process and modulate the force output of the involved muscle. Because the human connective tissue and skin layers have a low pass filter effect on the original signal, the analyzed firing frequency e.g. of a surface EMG does not present the original firing and amplitude characteristics. For simplicity, one can say that the EMG signal directly reflects the recruitment and firing characteristics of the detected motor units within the measured muscle (Fig. 18): Figure 18 Recruitment and firing frequency of motor units modulates force output and is reflected in the superposed EMG signal Adopted & modified
  • 30. 30 2.7 Nature of the EMG signal The “raw” EMG signal An unfiltered (exception: amplifier bandpass) and unprocessed signal detecting the superposed MUAPs is called a raw EMG Signal. In the example given below (Fig. 19), a raw surface EMG recording (sEMG) was done for three static contractions of the biceps brachii muscle: Figure 19 The raw EMG recording of 3 contractions bursts. When the muscle is relaxed, a more or less noise-free EMG Baseline can be seen. The raw EMG baseline noise depends on many factors, especially the quality of the EMG amplifier, the environment noise and the quality of the given detection condition. Assuming a state-of-the-art amplifier performance and proper skin preparation (see the following chapters), the averaged baseline noise should not be higher than 3 – 5 microvolts, 1 to 2 should be the target. The investigation of the EMG baseline quality is a very important checkpoint of every EMG measurement. Be careful not to interpret interfering noise or problems within the detection apparatus as “increased” base activity or muscle (hyper-) tonus! The healthy relaxed muscle shows no significant EMG activity due to lack of depolarization and action potentials! By its nature, raw EMG spikes are of random shape, which means one raw recording burst cannot be precisely reproduced in exact shape. This is due to the fact that the actual set of recruited motor units constantly changes within the matrix/diameter of available motor units: If occasionally two or more motor units fire at the same time and they are located near the electrodes, they produce a strong superposition spike! By applying a smoothing algorithm (e.g. moving average) or selecting a proper amplitude parameter (e.g. area under the rectified curve), the non- reproducible contents of the signal is eliminated or at least minimized.
  • 31. 31 Raw sEMG can range between +/- 5000 microvolts (athletes!) and typically the frequency contents ranges between 6 and 500 Hz, showing most frequency power between ~ 20 and 150 Hz (see chapter Signal Check Procedures) 2.8 Factors influencing the EMG signal On its way from the muscle membrane up to the electrodes, the EMG signal can be influenced by several external factors altering its shape and characteristics. They can basically be grouped in: 1) Tissue characteristics The human body is a good electrical conductor, but unfortunately the electrical conductivity varies with tissue type, thickness (Fig. 20), physiological changes and temperature. These conditions can greatly vary from subject to subject (and even within subject) and prohibit a direct quantitative comparison of EMG amplitude parameters calculated on the unprocessed EMG signal. Figure 20 The influence of varying thickness of tissue layers below the electrodes: Given the same amount of muscle electricity condition 1 produces more EMG magnitude due to smaller distance between muscle and electrodes 2) Physiological cross talk Neighboring muscles may produce a significant amount of EMG that is detected by the local electrode site. Typically this “Cross Talk” does not exceed 10%- 15% of the overall signal contents or isn’t available at all. However, care must been taken for narrow arrangements within muscle groups. ECG spikes can interfere with the EMG recording, especially when performed on the upper trunk / shoulder muscles. They are easy to see and new algorithms are developed to eliminate them (see ECG Reduction).
  • 32. 32 Figure 21 Raw EMG recording with heavy ECG 3) Changes in the geometry between muscle belly and electrode site Any change of distance between signal origin and detection site will alter the EMG reading. It is an inherent problem of all dynamic movement studies and can also be caused by external pressure. 4) External noise Special care must be taken in very noisy electrical environments. The most demanding is the direct interference of power hum, typically produced by incorrect grounding of other external devices. 5) Electrode and amplifiers The selection/quality of electrodes and internal amplifier noise may add signal contents to the EMG baseline. Internal amplifier noise should not exceed 5 Vrms (ISEK Standards, see chapter “Guidelines…”) Most of these factors can be minimized or controlled by accurate preparation and checking the given room/laboratory conditions.[6] 2.9 Physiology of EMG[1] Electromyography, also referred to as myoelectric activity, measures the electrical impulses of muscles at rest and during contraction. As with other electrophysiological signals, an EMG signal is small and needs to be amplified with an amplifier that is specifically designed to measure physiological signals. This signal can be recorded or measured with an electrode, and is then displayed on an oscilloscope, which would then provide information about the ability of the muscle to respond to nerve stimuli based upon the presence, size and shape of the wave – the resulting action potential. While the electrode could be inserted invasively into the muscle (needle electrodes), a skin surface electrode is often the preferred instrument, because it is placed directly on the skin surface above the muscle without employing the method of pinch insertion into the test subject. When EMG is measured from electrodes, the electrical signal is composed of all the action potentials occurring in the muscles underlying the electrode. This signal could either be of positive or negative voltage since it is generated before muscle force is produced and occurs at random intervals. The EMG signal is first picked up by electrode and amplified. Frequently more than one amplification stages are needed, since before the signal could be displayed or recorded, it must be processed to eliminate low or high frequency
  • 33. 33 noise, or any other factors that may affect the outcome of the data. The point of interest of the signal is the amplitude, which can range between 0 to 10 millivolts (peak-to-peak) or 0 to 1.5 millivolts (rms). The frequency of an EMG signal is between 0 to 500 Hz. However, the usable energy of EMG signal is dominant between 50-150 Hz. Figure 22 Frequency Spectrum of the EMG signal In order to obtain a signal that yields the maximum information, the method employed and the implementation device has to be considered. There are many dependent factors that could affect a surface EMG since the signal is susceptible to noise interference such as hum, signal acquisition such as clipping and baseline drift, skin artifacts, processing errors, and interpretation problems. For example, the contact of electrode to the skin could distort a recording signal. The inadequate amplification of the signal could cause a recorder detection problem. A wrong filter could efface some of desirable information of a signal. Moreover, there are other factors such as the distance between electrodes as well as the recording times used in the experiment. The device utilized in the measuring of the signal must also be considered since low-level input into a recording device could also affect data and yield inaccurate results. 2.9.1 Electrodes The EMG electrode could be explained by a receiving antenna concept. A receiving antenna is an electrical device that detects oscillating magnetic fields, which are generated from various sources. Then the signal is transmitted through the air from source to the receiving antenna, a concept that is used to engineer the design of electrode. In terms of recording the EMG signal, the muscle fiber is a biological signal generator, spreading out over voltage fields to the volume- conductivity surrounded by fluid. This fluid serves to convey an EMG signal to an electrode, like air carry signals to an antenna. The EMG recording starts from the beginning of the bioelectrical events. The changing conductivities in the membranes will make action currents flow across the membranes as well as into the extracellular fluids around active cells. The
  • 34. 34 extracellular currents will then generate potential gradients as they flow through the resistive extracellular fluids. The changing potential gradients, subsequently, will produce electrical currents in the electrode leads by capacitive conductance across the metal/electrolyte interface of the electrode contacts. These weak currents will then flow through the high impedance circuits of the amplifier input stages, which will then convert these currents into large output voltages. Figure 23 Surface EMG electrodes Figure 24 Ground electrode for surface EMG The EMG electrodes can be classified by using its geometry. There are six classes of EMG electrodes: monopolar electrode, bipolar electrode, tripolar electrode, multipolar electrode, barrier or patch electrode, and belly tendon electrode. A monopolar electrode takes potential from electrode and ground as the inputs to the differential amplifier. When measuring, only a bare electrode is placed, without utilizing other electrical connection. Because the ground yields a negative
  • 35. 35 input to differential amplifier, the potential from electrode is always based on ground. A bipolar electrode is used to measure the voltage different between two specific points. It generally must be used with a differential amplifier. A bipolar electrode has two contacts that are not connected to each other. Therefore, one node will be used for positive input, and the other will be used for a negative input for the differential amplifier. Because the differential amplifier treats both inputs equally, it will yield an accurate output. However the distance between the electrodes could affect the measurement result. Placing the electrodes too far from one another could yield a weak signal. On the other hand, placing them too close may also result in unusable data, since the amplifier preprocesses each inputs signal separately before subtracting those signals for output. A tripolar electrode has three electrodes that are placed at equal intervals along a straight line. The central electrode is usually connected to the positive input of a differential amplifier, while the electrodes on the sides are usually connected to the negative input of a differential amplifier. This configuration also requires another electrode to serve as a reference. The tripolar electrode is often used to record nerve potentials, as its configuration holds the advantage of being able to reject some forms of biological noise. A multipolar electrode consists of rows of bipolar electrodes where an equal lead is connected each side of bipolar electrodes to serve as a positive and negative input for a differential amplifier. Besides, another electrode must be applied as a reference point. The multipolar electrode is often used to record the activity of certain motor units based on idiosyncrasies in their fiber locations. The barrier or patch electrodes are typical bipolar electrodes that are closely connected to a dielectrical barrier. The dielectrical is a non conductive substance that is placed between the electrodes. This configuration redirects currents in extracellular flowing around the tissue nearby. The patch also keeps the currents that are generated from tissues on each side to prevent them from spreading into each other. Consequently, the potential gradient of a desired action is larger, and the potential gradient of an undesired action is smaller. A belly tendon electrode is one of the fields of interest in the clinical EMG. Its geometry is an interesting hybrid of the monopolar and bipolar approaches. In this technique, the first electrode is placed in or over the middle point of the muscle of the belly, which serves as the positive input to the amplifier. The second electrode is placed over the tendon of the same muscle, which is usually about the end of contractile elements, and serves as the negative input to the amplifier. This arrangement gives a clean leading negative waveform, since there is no virtual active contribution from tendon electrode. A belly tendon electrode is employed specifically for tendon applications although it is not used for measuring a selective muscle EMG recording during physiological activity.
  • 36. 36 All of electrode geometries discussed above could be considered as a dipole antenna in term of electrical behavior. Monopolar electrodes are used to measure the EMG signal of very small muscle. This is a good approach for sampling a signal that occurs near the surface of an active single fiber. On the other hand, tripolar electrodes and multipolar electrodes are used for sampling some large muscles. 2.9.2 EMG Electrode Placement 2.9.2.1 Location and Orientation of the electrode The electrode should be placed between a motor point and the tendon insertion or between two motor points, and along the longitudinal midline of the muscle. The longitudinal axis of the electrode (which passes through both detection surfaces) should be aligned parallel to the length of the muscle fibers. Figure provides schematic representation of the preferred electrode location. Figure 25 The preferred electrode location is between the motor point and the tedious insertion 2.9.2.2 NOT on or near the tendon of the muscle As the muscle fibers approach the fibers of the tendon, the muscle fibers become thinner and fewer in number, reducing the amplitude of the EMG signal. Also in this region the physical dimension of the muscle is considerably reduced rendering it difficult to properly locate the electrode, and making the detection of the signal susceptible to crosstalk because of the likely proximity of agonistic muscles. 2.9.2.3 NOT at the outside edges of the muscle In this region, the electrode is susceptible to detecting crosstalk signals from adjacent muscles. It is good practice to avoid this situation. For some applications, crosstalk signals may be undesirable. 2.9.2.4 Orientation of the electrode with respect to the muscle fibers The longitudinal axis of the electrode (which passes through both detection surfaces) should be aligned parallel to the length of the muscle fibers. When so arranged, both detection surfaces will intersect most of the same muscle fibers. Hence, the spectral characteristics of the EMG signal will reflect the properties of fixed set of muscle fibers in the region of the electrode. Also, the frequency
  • 37. 37 spectrums of the EMG signal will be independent of any trigonometric factor that would provide an erroneous estimate of the conduction velocity. The resultant value of the conduction velocity affects the EMG signal by altering the temporal characteristics of the EMG signal, and consequently its frequency spectrum. 2.9.2.5 Reference electrode placement The reference electrode (at times called the ground electrode) is necessary for providing a common reference to the differential input of the preamplifier in the electrode. For this purpose, the reference electrode should be placed as far away as possible and on electrically neutral tissue (say over a bony prominence).Often this arrangement is inconvenient because the separation of the detecting electrode and reference electrode leads requires two wires between the electrodes and the amplifier. It is imperative that the reference electrode make very good electrical contact with the skin. For this reason, the electrode should be large (2 cm x 2 cm). If smaller, the material must be highly conductive and should have strong adhesive properties that will secure it to the skin with considerable mechanical stability. Electrically conductive gels are particularly good for this purpose. Often, power line interference noise may be reduced and eliminated by judicious placement of the ground electrode. 2.9.2.6 Some Guidelines for use of surface EMG electrodes Skin Preparation - Alcohol removal of dirt, oil, and dead skin. - Shave excess hair if necessary. (Under ideal conditions this should always be done. However, it is not feasible in many cases.) - If the skin is dry, some electrode gel rubbed into the skin can help. - If the person is going to be sweating, spray an antiperspirant on the skin after cleaning with alcohol. Placement of Electrodes - There are specific references for different ways to measure for placement. - General guidelines for large muscle groups: 1. Best if over the largest mass of the muscle and align electrodes with muscle fibers. 2. Use motor point and motor point finder to locate (general location charts are available) Cross Talk - Not a real problem with large muscle groups. - Can sometimes be avoided my adjusting the electrode size, inter- electrode distance (if an option on your brand of electrode), or by use of fine wires. Application - Skin placement.
  • 38. 38 - Avoid movement of electrodes by using straps or tape to firmly secure electrode in place. - Avoid bending of leads, place leads pointing in the direction that you want the wire to continue in. (e.g., For electrodes placed on an extremity, have the lead pointing towards the proximal end of the extremity so that the wire will not have to be bent in order to go in the proximal direction.) - Avoid any stress on the wires by making sure that the wires are loose underneath the tape or wrap that is holding them in place. Be sure to check when the wires cross the joint that once the joint is fully extended the wires are not drawn taunt. - Avoid placing electrodes over scars. Testing - Do manual muscle tests to assure that you are getting a signal and that you are over the intended muscle. - Do trial session to check signal and to get subject used to the setup and how instrumented. 2.9.3 Amplifier of EMG signals[6] The amplifier is an electronic device that serves to boost low power signal to higher power signal that is usable to perform work. There are two reasons to amplify the signal. First, amplification increases the level of signal enough to protect an electrical interference during transmission. Second, the signal is amplified so that it could be stored in a storage device, or displayed by a measurement device like oscilloscope. In case of an EMG signal, an amplifier is necessary. There are no such devices that can measure EMG signal without amplification. A differential amplifier is used to amplify an EMG signal, as it has the ability to eliminate the noise from the signal. As shown in Figure 26 the differential amplifier takes two inputs, subtracts them and amplifies the different. In this case, if there is noise interference through the input wires, the noise could be circuitry canceled out so long the transmission of the two inputs is completely symmetrical manner. It is difficult to make an amplifier with perfect subtraction. The Common Mode Rejection Ratio (CMRR) could measure the accuracy of subtraction in each amplifier. It is suggested to have a CMRR value at 90dB in order to sufficiently discard a contaminated noise. Yet with modern technology, the differential amplifier could make a CMRR value of 120dB. However, even though a differential amplifier has the ability to reduce unwanted noise signals that occur from both sides of the input wires, contaminated noises could still exist. This noise could have been injected into the signal by a stray capacitance that has been amplified, and thus, degrading the signal.
  • 39. 39 Figure 26 A schematic of the differential amplifier configuration Every electronic component or even an amplifier itself behaves as an effective filter, since there are no such electronic devices that can transfer all frequency range. The electrode itself tends to have lower impedance for a higher frequency and have higher impedance for a lower frequency. The connection of electrode, cable and amplifier creates an implicit filter effect. The electrode contacts are connected in series to an amplifier; they function similar to that of a capacitor, while an impedance of amplifier is similar to that of a resistor. This connection visualizes a High-Pass filter circuit. The low frequency voltage tends to be attenuated and drop the highest voltage across the electrode contacts rather than the amplifier. On the other hand, the cables that connect electrodes to an amplifier have a stray capacitor behavior. It is considered that this capacitor is connected to ground, which simulates a Low-Pass filter circuit. The stray capacitor will provide low impedance, at which the high frequency picked up by electrodes tend to drop their voltage here. Therefore an amplifier will see an attenuation of high frequency. The implicit filter could cause signal problems if it is not considered carefully in the design of an amplifier. The explicit filter with real components (resistor and capacitor) functions by using the same concept of an implicit filter, and could help in increasing the signal-to-noise ratio. Since a signal is desired to be within in some frequency range, it is good idea to have an explicit filter for that particular band. Therefore, noise with the frequency outside a desired frequency band will be distorted. 2.9.3.1 Problem with noise and artifacts[1] In the process of recording an EMG signal, the source of the generated signal is not only from bioelectrical generator or active cell, but also from any electrical fields that occur around an electrode and lead cables. These electrical fields produce some signals that could also be added to an EMG signal, causing a form of interference that is called noise. Interference noise can be produced from anything that has an electrical field such as power lines, computer monitors, transformers, or EMG amplifier itself. Once noise has occurred, it could cause problem in recording an EMG signal. Therefore while planning out the design of the amplifier device and recording the
  • 40. 40 EMG signal, noise factors should be taken into consideration, since noise could come from a variety of sources such as electronic components, recording devices, ambient noise, motion artifacts, or inherent instability of the signal. Any electronic devices can produce noise. The noise frequency is range between 0 Hz to a 1000 Hz. This kind of noise cannot be eliminated. Using an intelligent circuit design and a good quality of electronic components to construct the device can only reduce the noise. Ambient noise could be generated from any electronic device that created an electromagnetic field such as televisions, computer monitors, motors, electrical power lines, fluorescent lamps or light bulbs. In fact there are radio waves and magnetic fields floating all over our body. It is virtually impossible to drain these radiators to ground (earth surface). The ambient noise also cannot be avoided. The ambient noise frequency occurs primarily within the range 50 Hz or 60 Hz, while the amplitude of an ambient noise is about one to three times greater than that of an EMG signal. Motor artifacts come from two sources; first, from the contact of an electrode to skin; second, from the connection of cable from electrode to the amplifier. When performing a grasping experiment, a movement of the wire alone could cause a noise problem. This electrical noise from both sources has the frequency range between zeros to twenty hertz. However, a proper design of circuitry with a good connector and stable electrode contact could reduce this motion artifact problem. Inherent instability of the signal is caused by a nature of EMG signal. The amplitude of the EMG signal frequency range between zero hertz to twenty hertz is particularly unstable due to the quasi-random nature of the firing rate of motor units. It is suggested to consider an EMG signal frequency in this range as an unwanted noise signal. There is no boundary in what amplitude of an EMG signal is good for yielding accurate recordings. While a certain amount of noise could be tolerated, the question is exactly how much noise could be allowed. In other words, there is a question about the tolerable levels of the signal-to-noise ratio. The signal-to-noise ratio is determined by taking the ratio of the amplitude of desire signal over the amplitude of added noise signal. The main concern now is in the lever of the signal-to-noise ratio that could degrade an analysis result. If the noise is produced from thermal motion, then twice of desired signal amplitude over the noise amplitude is good enough. However, if the noise occurred periodically and forms a pattern similar to the desired signal, it is suggested that ten times grater of the desire signal amplitude than the noise amplitude would be clarified a confusing event. In order to determine signal-to-noise ratio, the study of noise behavior alone may be required to see how noise could affect the real signal. 2.10 Definition of Pulse (Heartbeat) rate:[7] In medicine, one's pulse represents the tactile arterial palpation of the heartbeat by trained fingertips. The pulse may be palpated in any place that allows an
  • 41. 41 artery to be compressed against a bone, such as at the neck (carotid artery), at the wrist (radial artery), behind the knee (popliteal artery), on the inside of the elbow (brachial artery), and near the ankle joint (posterior tibial artery). The pulse can also be measured by listening to the heart beat directly (auscultation), traditionally using a stethoscope. 2.10.1 Physiology The pulse is a decidedly low tech/high yield and antiquated term still useful at the bedside in an age of computational analysis of cardiac performance. Claudius Galen was perhaps the first physiologist to describe the pulse. The pulse is an expedient tactile method of determination of systolic blood pressure to a trained observer. Diastolic blood pressure is non-palpable and unobservable by tactile methods, occurring between heartbeats. Practitioners in Chinese Medicine are trained in Pulse Diagnosis and seek six different pulses in each wrist, each corresponding to specific organs of the body. The Chinese practitioner is trained to evaluate the frequency, rhythm and volume of the pulse and may characterize it as strong, thready, slippery or floating. Pressure waves generated by cardiac systole move the artery walls, which are pliable and compliant. These properties form enough to create a palpable pressure wave. The Heart Rate may be greater or lesser than the Pulse Rate depending upon physiologic demand. In this case, the heart rate are determined by auscultation or audible sounds at the heart apex, in which case it is not the pulse. The pulse deficit (difference between heart beats and pulsations at the periphery) is determined by simultaneous palpation at the radial artery and auscultation at the heart apex. Pulse velocity, pulse deficits and much more physiologic data is readily and simplistically visualized by the use of one or more arterial catheters connected to a transducer and oscilloscope. This invasive technique has been commonly used in intensive care since the 1970s. The rate of the pulse is observed and measured by tactile or visual means on the outside of an artery and is recorded as beats per minute or BPM. The pulse may be further indirectly observed under Light absorbance’s of varying wavelengths with assigned and inexpensively reproduced mathematical ratios. Applied capture of variances of light signal from the Blood component Hemoglobin under oxygenated vs. deoxygenated conditions allows the technology of Pulse Oximetry.
  • 42. 42 Figure 27 pulse rate basic 2.10.2 Normal Pulse Rates: Normal pulse rates in beats per minute (BPM): Newborn 1 – 12 months 1 – 2 years 2 – 6 years 6 – 12 years 12 years - adults adult athletes 120 - 160 80 - 140 80 – 130 75 – 120 75 – 110 60 - 100 40 - 70
  • 43. 43 3.0 Taxonomy of wireless medical systems A wireless surface electromyography system is a taxonomy that categories existing wireless medical system. Multiple wireless sensor applications have been proposed to help user our society into a wireless future. Examples of such applications include security, military, medical, environmental, and industrial/ building automation. The medical industry has embraced wireless sensor networks as more and more innovative developments have evolved and confirmed that wireless sensor networks are a valuable complement to current medical system. A methodology for categorizing wireless medical system (WMS) has been developed based on system function, technology, hardware components (including sensors) and application. The second level of the taxonomy categories the wireless technology implemented within each medical system. Typical wireless medical systems communicate within unlicensed frequencies. Table 1 shows a characteristic graph that compares common unlicensed wireless technologies, namely Bluetooth, ZigBee and Wi-Fi (Wireless Fidelity). This section explains the characteristics of each of these technologies. Table 1 Wireless technologies characteristic graph 3.1 Radio Frequency In the United States the Federal Communication Commission regulates the use of industrial, scientific and medical (ISM) radio bands. The ISM radio band was originally reserved internationally for the license-free use of RtaF electromagnetic fields. In license-free radio bands, users don’t have to purchase a license and the spectrum is widely available. This allows WMS to wirelessly transmit medical sensor data on ISM radio bands without having to purchase an expensive license. In recent years, the ISM license-free radio frequencies have been used for communication technologies such as Wi-Fi, Bluetooth and ZigBee. The more
  • 44. 44 commonly used license-free RF bands are 900MHz, 1.8GHz, and 5.8GHz. The two methods for radio frequency modulation in the unlicensed 2.4GHz ISM band are frequency-hopping spread spectrum (FHSS) and direct-sequence spread spectrum (DSSS). FHSS is a spread-spectrum method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. DSSS is a modulation technique in which the transmitted signal takes up more bandwidth than the information signal that is being modulated. The 900MHz radio frequency band is for unlicensed use only in North America, Australia and Israel, while the 2.4 GHz radio frequency band can be used worldwide (including North America, Australia and Israel). Wi-Fi is a wireless networking protocol based on the IEEE 802.11 specifications. The primary motivation for Wi-Fi is data throughput. Wi-Fi is typically used to connect computers to wireless local area networks (WLAN) and indirectly to the internet. Wi-Fi devices transmit at frequencies of 2.4 GHz or 5 GHz. Wi-Fi uses DSSS, with each channel being 22 MHz wide, allowing up to three evenly- distributed channels to be used simultaneously without overlapping each other.[5] 3.2 Bluetooth Many companies such as Sprint, Motorola and Microsoft have incorporated Bluetooth into mobile phones, portable computers, cars, stereo headsets, MP3 players, etc. Bluetooth is a short range low power, low cost communication standard that uses radio technology. Originally, in 1984 Bluetooth was envisioned as a cable-replacement technology. In 1999 seven companies teamed up and formed a group called the Bluetooth Special Interest Group (SIG). The SIG developed Bluetooth into an attractive compatible wireless standard. Three different classes of Bluetooth radios exist, class 1, class 2, class 3. Each with different operating ranges. A class 1 radio has an operating range of up to 100 meters, class 2 up to 10 meters, class 3 up to 1 meter. There are two core specification versions of Bluetooth, both with different data rates; Version 2.0 has an enhanced data rate of 3 Mbps and Version 1.2 has a basic data rate of 1 mbps. Batteries powering a Bluetooth device have a very short life expectancy, usually a few days. Bluetooth devices can from a personal are network called a piconet. A piconet is an ad-hoc computer network of devices using Bluetooth technology protocols to allow one master device to interconnect with up to seven active slave devices. Piconets can communicate with each other, thus allowing devices that are out of range to communicate through several hops from one piconet to the other.[2]
  • 45. 45 Figure 28 Bluetooth Protocol Stack Bluetooth protocol stack is illustrated in the radio layer is primarily concerned with the design of the Bluetooth transceivers. The baseband layer defines how Bluetooth devices search for and connect to other devices. The master and slave roles are defined her, as are the frequency-hopping sequences used by devices. The baseband layer supports two types of links: Synchronous Connection Oriented (SCO) and Asynchronous Connection Less (ACL). SCO links are characterized by a periodic, single-slot packet assignment, and are primarily used for voice transmission that requires fast, consistent data transfer. A device with an ACL link can send variable length packets of 1, 3 or 5 time-slot lengths. The link manager layer manages the properties of the air interface link between devices. The logical link control and Adaptation Protocol (L2CAP) layer provides the interface between the higher-layer protocols and the lower-layer protocols. L2CAP allows multiple protocols and applications to share the air- interface. L2CAP is also responsible for packet segmentation and reassembly, and for maintaining the negotiated service level between devices. The Host Controller Interface (HCI) layer defines a standard interface for upper level applications to access the lower layers of the stack. A Bluetooth transceiver uses frequency hopping-spectrum (FHSS) in the unlicensed 2.4 GHz ISM frequency band. This data transmission technique makes signals difficult to intercept because FHSS signals sound like momentary noise bursts. Typically, 79 channels are available for a Bluetooth device. A device can only operate on a channel for 0.4 seconds within a 30 second window, and transmits using pseudorandom hops across all 79 channels at a rate of 1600 hops per second. Bluetooth devices use a polling technique to transmit packets. The master device transmits only in even numbered time slots. The slave devices transmit only in odd numbered time slots. A different frequency channel is use in each time slot.[7] 3.3 ZigBee ZigBee has become attractive wireless standard due to its reliable cost, effective low power wireless network capabilities. Zigbee is based on an open global standard and its primarily used for short range wireless application. For this
  • 46. 46 reason many industries has opted to apply the Zigbee standard within their product monitoring and control application. ZigBee is wireless standard based technology that addresses the need for remote monitoring and con troll and censoring network application it enables the deployment of large cintite of wireless networks with low cost and low power solutions and provides the ability to operate for years on inexpensive batteries. zigbee is built on IEEE 802.15.4 wireless, personal area network standard and uses the unlicensed radio band 2.4GHz, 868MHz and 915 MHz the zigbee standard uses direct sequence spread system (DSSS) for radio frequency modulation over 16 channel each channel occupies 3MHz and its centered 5MHz from adjacent channels, giving a 2 MHz gap between pairs of channels A zigbee network usually consists of one master device one or more slave device and operational router. The master device responsible for establishing a network with a personal area network identifier the slave devices can be programmed to sleep so that battery power is conserved. The wireless technology characteristic says that zigbee transmit at a slower data rate, 250 KBPS than the other wireless standards however this transmission rate is ideal for system that intermittently transmit small amounts of data. Because zigbee performs just a few specific, simple task the protocol stack can be as small as 28KB, therefore the system controller requires less energy and consumes less power. The small amounts of data that are transmitted also contribute to systems minimal energy consumption. Bluetooth device consumes more power because they are typically constant lay on and don’t spend much time sleeping whereas zigbee slave devices spend a majority of their time sleeping Zigbee clearly has advantage over other wireless technique when network size is considered a zigbee network can deploy over 65500 sensor nodes within network system this nodes count gains over Bluetooth 7, Wi-Fi 32 by a sizeable margin on the attractive feature of zigbee is its ability to transmit data up to 300 meter or up to 30 times farther than Bluetooth and 3 times farther than Wi-Fi.
  • 47. 47 Figure 29 ZigBee Protocol Stack Zigbee network can arrange in three different topology mesh, tree and star. The mesh topology nodes connect to communicate directly with a coordinator or router. The Wi-Fi server communicate routes may exists. Only the node that data is intended for reacts in star topology zigbee network contains one coordinator, no router and no of devices that are all within range of the coordinator. The third topology arranges communicate routers so that true exist exactly one route from one device to another.[4] Zigbee Bluetooth WiFi Applications: Monitoring and control Cable replacement Web, video email Data capacity (Kbps): 250 1,000 11,000+ Range (meters): 70 10 100 Battery life Years Days Hours Nodes per network 255 - 65,000 8 30 Software size (Kbytes): 4 - 32 250 1,000+ Table 2 ZigBee Uperhand
  • 48. 48 4.0 System design 4.1 Block Diagram: Figure 30 Block diagram 4.2 EMG amplifier Figure 31 Burr brown amplifier As explained earlier, EMG signal is so small that computer could not read it. While the amplitude of the signal is between 0 to 10 mill volts (peak-to-peak), the usable frequency of an EMG signal is ranging between 50-150 Hz [1]. At this state, we need a huge gain (about thousand times) to boost the EMG signal without changing phase or frequency of the signal. This amplifier uses a typical differential amplifier circuit, which contains two inputs (positive input and negative input). The differential amplifier circuit subtracts two inputs and amplifiers the difference. To get the right level of the input signal, we need a body reference which works as a feedback from the inputs. Whenever the signal changes due to noise introduced by the body, this body reference will help maintain the correct level of signal. LCD Display ADC Microcontroller ZigBee Transmitter ZigBee ReceiverDACMicrocontroller Pulse Sensor & EMG Electrodes GSM Module
  • 49. 49 4.3 Instrumentation Amplifier Figure 32 Burr brown using lm 124 A suitable operational amplifier (op-amp) for this type of application is the Instrumentation Amplifier. Its versatile 3-op amp design and small size make it ideal for a wide range of applications. This type of op-amp usually provides excellent accuracy because it provides high bandwidth even at high gain. The EMG amplifier used a BURR-BROWN, lm124 chip for the amplifier, as suggested by the application information data sheet of lm 124. The gain of the amplifier can be adjusted by changing the resistor Rg between pin number 1 and 8. 4.3.1 Low pass filter: Figure 33 4th order LPF When handling pulse trains and signal bursts of EMG signals, it might be favorable to use filters which have negligible over-shoot. When handling pulse trains and signal bursts, it might be favorable to use filter which have negligible
  • 50. 50 over shoot in the step response. A class of filters particularly suitable for this type of signals is the Bessel filter. The phase characteristics of this class of filters exhibit a linear increase with frequency. The group delay, defined as the derivative of the phase with respect to frequency, is hence extremely flat over a wide range of frequencies. Frequency range of EMG signal is between 50-150Hz so 4th order Bessel filter is required for the low pass filtration of 150Hz. Figure 34 Low pass Filter design
  • 51. 51 4.3.2 High pass filter: Figure 35 1 st order HPF The dominant energy of the EMG signal is located in the 50-150 Hz range, to eliminate the movement artifacts, inherent instability of the signal which ranges between 0 to 15 Hz and the ambient noise arises from the 60 Hz 1st order high pass filtration of 50Hz is required. Figure 36 High pass filter design
  • 52. 52 4.4 Pulse monitoring system Figure 37 Pulse monitoring system 4.5 design description 1) Instrumentation amplifier. IC INA 128 INA 131 INA 217 INA 333 Gain(vv) 1 to 10000 100 1 to 10000 1 to 1000 CMRR(db) 120 110 100 100 Bandwidth(KHz) 200 70 800 800 IP Bias current(namp) 5 2 12 0.2 Noise(nv) 8 12 1.3 25 Table 3 Instrumentation amplifier comparison Selection (INA 128): After brief literature survey & discussion I come to know that INA128 instrumentation amplifier is well suited for our project because its low offset voltage, low input bias current, low drift and high CMRR. 2) Quadruple Operational Amplifiers. IC LM 124 LM 224 LM 324 OPA 4131 GBW(MHz) 1.1 1.2 1.2 3 CMRR(db) 70 70 65 50 Noise(nv) - 35 35 42 No. of Channels 4 4 4 4 Cost us$ 0.29 0.11 0.11 0.40 Table 4 Quad selection comparison
  • 53. 53 Selection (LM 124) : After brief literature survey i have selected LM 124 because it provides high performance at low cost. 3) Wireless device Zigbee Bluetooth WiFi Applications: Monitoring and control Cable replacement Web, video email Data capacity (Kbps): 250 1,000 11,000+ Range (meters): 70 10 100 Battery life Years Days Hours Nodes per network 255 - 65,000 8 30 Software size (Kbytes): 4 - 32 250 1,000+ Table 5 Wireless device selection 4) Electrode selection Type of Electrodes Selected electrode Reason Surface Electrodes, Needle Electrodes Surface electrode These electrodes are not very expensive and easy to use as compared to needle electrodes. Table 6 Electrode Selection
  • 54. 54 5) Microcontroller selection Type of Microcontroller Selected Reason AVR, 8051 AT89s52 Easy to use, Availability cost of the product. Table 7 Microcontroller Selection 6) Comparator selection IC LM 158 LM 258 LM 2904 LM 358 GBW(MHz) 0.7 0.7 0.7 0.7 CMRR(db) 70 70 70 70 Noise(nv) - 40 40 40 No. of channels 2 2 2 2 Cost(US$) 1.62 0.11 0.12 0.10 Table 8 Comparator Selection Selection (LM 358) : After a brief study I have selected LM 358 because it gives efficient performance at low cost and easily availability.
  • 55. 55 4.6 Transmitter circuit diagram Figure 38 Transmitter circuit diagram
  • 56. 56 4.7 Receiver circuit diagram: Figure 39 Receiver circuit diagram
  • 57. 57 5.0 Programmer description for system Figure 40 keil software
  • 58. 58 Figure 41 X-CTU Figure 42 Filter pro
  • 59. 59 5.1 Observed signals Recorded samples from the digital oscilloscope using the developed EMG amplifier device. The samples were recorded in real time from real human hand. The experiment preformed grasping of objects of different sizes and shapes. 1. Vpp = 484mV, Frequency =140.4Hz 2. Vpp = 448mV, Frequency =129.5Hz
  • 60. 60 3. Vpp = 376mV, Frequency =146.2Hz 4. Vpp = 340mV, Frequency =140.8Hz
  • 61. 61 5.2 Flowchart 5.2.1 TX section flowchart
  • 62. 62 5.2.2 RX section flowchart
  • 63. 63 5.3 Pulse rate result Figure 43 Put the finger Figure 44Observe the TX pulse
  • 64. 64 Figure 45 Observe the RX pulse Figure 46 Lcd display
  • 65. 65 5.4 Emg result Figure 47 Place the electrode Figure 48 Push the muscle fiber
  • 66. 66 Figure 49 Observe the RX pulse Figure 50 Observe the pulse on LCD
  • 67. 67 Figure 51 Reception of alert message Figure 52 Read the message
  • 68. 68 5.5 result Suggestions for further advancements The feasibility of the signals can be improved using suction cup electrodes rather than the Peel-and-stick surface electrode. The use of surface electrode was owing to the unavailability of the suction cup electrode and the cost constraints. Better performance can also be obtained with the help of electrodes with built in preamplifiers. The signals obtained from the body can be converted into digital form and can be further processed digitally using digital processors to carry out various analysis related to the muscular structure as well as their functioning. The microcontroller incorporated in the project can be used as a base to work upon and develop various functionalities such as emergency braking, obstacle detection and many more. The EMG amplifier, the size of the enclosure should be considered. The electrode extensions should be eliminated. The amplifier should be able to hold electrodes directly on the unit. The amplifier and electrode holders could be placed in the same PCB which has a connector to transfer the output to the microcontroller unit. This amplifier unit would be then placed directly on the hand. 5.6 Application area of project Currently there are three common applications of the EMG signal. 1.To determine the activation timing of the muscle; that is, when the excitation to the muscle begins and ends. 2. To estimate the force produced by the muscle. 3. To obtain an index of the rate at which a muscle fatigues through the analysis of the frequency spectrum of the signal. To observer the change in patient heart Rate fluctuation. In the not so distant future, we can expect applications in the assessment of neurological diseases which affect the fiber typing or the fiber cross-sectional area of the muscle. The relationship between the force produced by the muscle and the amplitude of the EMG signal requires further description. During the past five decades, the scientific literature has promulgated an apparent controversy on this issue. Some reports describe a relatively linear relationship, whereas others describe a relative on-linear relationship, with the amplitude of the EMG signal increasing greater than the force. Where the firing rate of the motor units has a greater dynamic range and motor unit recruitment is limited to the lower end of the force range, the relationship is relatively linear. Whereas, in larger muscles where motor unit recruitment continues into the upper end of the force range and the firing rate have a lower dynamic range, the relationship is relatively non-linear. In the applications discussed herein, data collected via the neural implant were directly used for control purposes, thereby removing the need for any other external control devices. To control an electric wheelchair, a sequential –state machine was implemented, with a command signal decoded in real time
  • 69. 69 from the neural signals being used to halt the cycle at the intended action. In this way, the overall control of the wheelchair was made to be as simple as possible. Initial experiments involved selective processing of the signals obtained from several of the electrodes on the array over time to produce the discrete direction control outputs. With a small amount of learning time, the subject was able to control the direction and velocity of the fully autonomous mobile robot. On board sensors allow the robot to the override commands from the user to safely navigate local objects in the environment. The technique was further implemented on an electric wheelchair. With the command signal from the implant controller received by the wheelchair’s driver mechanism via a short-range digital radio link. The command signal essentially obtained by the user closing his hand, halted the sequential state machine at the desired output. The action of the sequential state machine was indicated by a number of light-emitting diodes positioned in front of the user on the right arm of the chair. These actions corresponded to the wheelchair motions of forward, backward, left, and right.
  • 70. 70 Conclusion & Future work The WPMG system has been developed and tested that support single channel. The WSEMG amplifier device is designed to amplify EMG signals from muscle groups on the upper forearm. The footprint of the complete system includes electrodes, amplifier, filters, microcontrollers and ZigBee Modems. The EMG amplifier uses skin surface electrodes as input sensors. The amplifier is a battery powered differential instrumental amplifier which raises very weak and noisy EMG signals to a stable level for wireless transmission. The filter is applied to select only the bandwidth of signals that is of interest for the underlying applications. The microcontrollers and ZigBee modems are used for wireless transmission of EMG signals. The major problems in developing the above listed components were to reduce noise, moving artifacts, system grounding and DC bias. Simillarly we can see noisy pulse rate signal on the receiver side.All these problems were successfully solved through the following steps: 1. Proper choice of discrete components (resistors, capacitors, and ICs). 2. Proper design of circuitry. 3. Final implementation of the device using PCB technology. 4. Systematic experimentation with the prototype (implemented on a breadboard). 5. Extensive testing of the device after implementation and executing final corrections. The concerns over the systems are: 1. Size of the system. 2. Distance over which data needs to travel. 3. Cost of the system. In future I can use some more physiological data like temperature, blood pressure, blood flow and technological data like ECG, EEG and data like to observe the patient completely and analysis the full body parameter using wireless media like ZigBee. So in future doctor can analysis the patient totally from remote location. if we can able to achieve the operation it will open a door in wireless biotelemetry domain to the next level of research.
  • 71. 71 References BOOKS: 1) Cromwell: “Biomedical Instrumentation and measurement.” 2) R.S. Khandpur : “Handbook of Biomedical Instrumentation.” 3) Braumwald, Fauci: “Principles Of Internal Medicine Volume 2” IEEE papers: 1) M. Steyaert, S. Gogaert, T. Van Nuland, and W. Sansen, .A low-power portable telemetry system for eight-channel EMG measurements,. In Proc. Annu. Int. IEEE-EMBS Conf., vol. 13, 1991, pp. 1711.1712. 2) Masayuki Ohyama, Yutaka Tomita, Satoshi Honda, Hitoshi Uchida, Noriyoshi Matsuo “Active Wireless Electrodes for Surface Electromyography,” 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Amsterdam 1996. 3) Chien C.-N., Hsu, H.-W., Jang J.-K., Rau C.-L., and Jaw F.-S., “Microcontroller-based wireless recorder for biomedical signals,” Proceedings of the 2005 IEEE Engineering in Medicine and Biology 27th Annual Conference Shanghai, China, September 1-4, 2005. 4) Geer, D., “Users Make a Beeline for ZigBee Sensor Technology,” IEEE Computer Society, Vol. 38, pp 16-19, December 2005. 5) McDermott-Wells, P., “What is Bluetooth?,” IEEE Potentials, Vol. 23, pp 33 – 35, December 2004. 6) Emly, M.S., Gilmor, L.D., and Roy, S.H., “Electromyography,” IEEE Potentials., Vol. 11, pp 25-28, April 1992. 7) Patrick Kinney, “ZigBee Technology: Wireless Control that Simply Works,” Communications Design Conference, 2 October 2003. Weblinks: 1) XB24 Data Sheet, “XBee RF module”, Digi International/Maxstream. http://www.digi.com/pdf/ds_xbeemultipointmodules.pdf 2) “Bluetooth Specia Intrest Group,” http://www.bluetooth.com/English/Technology/Pages/Basics.aspx 3) http://www.electrodestore.com/EMG/EMG.lasso?ran=5FDEED88&S=6&T=15 4) http://www.scribd.com/doc/23709010/Wireless-Bio-Telemetry 5) http://www.scribd.com/doc/54253401/Bio-Telemetry-Final-Report
  • 72. 72 Appendix