Jordan University of Science & Technology Faculty of Engineering. Department of Biomedical Engineering BME 443. Biomedical Instrumentation Lab I

Transcription

1 Jordan University of Science & Technology Faculty of Engineering Department of Biomedical Engineering BME 443 Biomedical Instrumentation Lab I Modified by Dr.Luay Fraiwan and Eng.Roba AL.Omari 2009/2010

2 Table of Contents Exp# Title Page 0 Introduction 3 1 Differential Amplifiers 5 2 Optoelectronic Components Band-Pass, Notch and other filters Noise in Biomedical Amplifier System The Electrocardiograph Recording (ECG) I. Analog to Pulse Shaping. II.Visual and Sound Pulse Indicators. Rate Meters I. Pulse Rate digital meters. II. Pulse rate by photopllethysmography. Galvanic Skin Resistance GSR Temperature Measurements Respiratory Rate EMG and EEG Reference: SIP385BM Biomedical Instrumentation Author: Morris Tischler

3 Introduction The course contains two pre wired panels with a variety of cables and accessories. It provides training in basic monitoring circuitry, such as ECG, EEG, EMG, Pulse rate, GSR, and temperature monitors. The first part of this lab explains the electronic circuit of the Electrocardiograph (ECG) Instrument in addition to EMG and EEG. The electrocardiograph recorder is an instrument which can record the low-level voltages produced by the heart. Recorded from a patient's limbs and chest, these voltages produce a tracing called an electrocardiogram. Since magnetic power fields create common-mode signals which interfere with the desired signal, special amplifier designs are needed. Figure#1 shows the block diagram of the experimental circuit on panel SIP385-1.This circuit will be more fully described in the experiments 1, 2, 3, 4,5,6,7 and 8 in addition to exp# 14 and 15.

4 The ECG amplifier (Instrumentation amplifier, section B) is a narrow band-pass, high gain amplifier system (series of amplifier stages) with a differential input. The differential-input, high impedance amplifier is capable of recording a range of heart produced voltages from less than one millivolt to almost one volt, even when artifacts and a high level of man-made electrical interference are present. The frequency response is in the range of (0.3 to 50) Hz The second part, explains the electronic circuit of Pulse Rate Digital meter, Temperature Digital Meter and Galvanic Skin Resistance. Figure #2 shows the block diagram of the experimental circuit on panel SIP This circuit will be more fully described in the experiments 9,10,11,12 and 13

5 EXP#1: Differential Amplifiers Theory; Biological potentials on a patient are measured at two distant points. The body, however, also picks up undesired potentials from radiated magnetic fields. The instrument chosen to measure biological potentials must therefore be able to reduce these extraneous signals. The input stage of a biological instrument typically employs a differential rather than a single- ended amplifier. The former is preferred because it has the capacity to amplify the differential signal and to attenuate the induced (commonmode) signal produced by magnetic fields, power line field (50or 60Hz) and man-made electrical noise. A single- ended amplifier amplifies both the biological potential and induced voltage. Of key importance is the ratio of [differential signal gain (A diff )] to the [common mode gain (A cm )]. This relationship is called common mode rejection ratio (CMRR) and is expressed by equation CMRR 20 log Adiff Acom The (CMRR) shows the ability of a differential amplifier to attenuate common mode signals appearing simultaneously with differential signals. In determining the CMRR, the two signals are adjusted at the input to produce the same output voltages (Vout cm = Vout diff ). Therefore, CMRR can be determined from the input voltages as shown below: CMRR Vin Vin cm diff Good amplifiers have CMRR values, which range from +60dB to +100dB. The adverse effect of electrode contact resistance on signal input is an additional consideration. Losses incurred at the lead contacts with the skin decrease the available input signal to each amplifier. High input impedance of the amplifier minimizes the signal loss. Since the LF347 has an input impedance of over ohms, only a very small portion of the input signal voltage would be lost. Since the LF347 is a quad as shown in Figure#3, three of the amplifiers (A2, A3 and A4)can be used for

6 recording the ECG, EMG, or EEG signal voltage. Two amplifiers (A2 and A3) are used for the differential input, and one for a single-ended output amplifier. A typical circuit arrangement is shown in section B in the insertion panel. Amplifier A1 is used in section A as an inverter. Section A: Differential Source We use the function generator instead of an ECG simulator (or human) in the first exp's to perform the experimental procedure. Therefore, section A is used to develop two signals out of phase from a single-ended function generator and the difference between them is in mv (to simulate the low-level voltages produced by the heart (QRS wave)). The following two equations are for the input voltages to the instrumentation amplifier (section B) when the mode switch in section A is set to the DIFF and COMM respectively: DIFF : Tp Tp 2 3 Tp Tp 1 1 R R R R R R Tp Tp COMM : Tp 2 Tp 2 Tp 1 Vin (diff) = Tp 3 -Tp 2 and Vin (cm) =Tp 2 +Tp 3

7 Section B: Differential Amplifier The gain of the amplifier A4 is determined by the ratio of the R11/R8 (100 K / 8.2K ) resistors (A = 12.2). The gain of the two amplifiers (A2 and A3) is determined from A diff 2 R R The overall gain = Gain (A2, A3) Gain (A4) = = approx 358 The gain of the input stage can be controlled by varying the resistor (R5) between pins 6 and 13. As the resistor is made smaller, the gain is increased. This resistor should not be zero since the circuit might oscillate under high gain conditions. In the circuit shown in the panel, resistors of 1% tolerance (or less) should be used, since both halves of the circuit must match. The value of potentiometer R10 should be adjusted to obtain the best balance of the two signals input to A4. This balance achieves the highest possible CMRR. ***************************************************************** Objectives: 1. Test and evaluate differential amplifiers as use din biomedical instrument 2. Determine the gain and common-mode rejection ratio of differential amplifiers. Materials Required: 1. Insertion Panel SIP DMM. 3. Jumper Lead. 4. Oscilliscope. 5. Function Generator. Experimental Procedure: 1. Balancing the Differential Amplifier (A 4 ).

8 Input: Using the function generator feed a 10 Hz sin wave and 1 Vp-p into Tp1 (Section A). Output: Is taken from Tp 6 using the digital scope. a. Set the mode switch in section A to the COMM position. b. Adjust R 10 (section B) as necessary for minimum sin wave output at Tp 6. TP 6 =.. 2. Single Ended Gain (One Input (Tp 3 )). Input: Using the function generator feed a 10 Hz sin wave and 1 Vp-p into Tp 1 (Section A). Output: Is taken from Tp6 using the digital scope. a. Set the mode switch in section A to the DIFF position. b. Using alligator (jumper) lead, connect the Tp2 input to the common (floating) ground. c. Measure the p-p signal voltages at: Tp 4... Tp 5 Tp 6 d. Calculate the single ended gain between Tp 3 and Tp 6. A s V V TP 6 TP 3. e. Using the digital scope, connect Tp 4 to channel 1 and Tp 5 to channel 2 and draw the wave shapes of the signals. Channel 1.. Channel 2.. Are the two signals out of phase (phase shift = 180)? Differential Gain (Two inputs: Tp 2 and Tp 3 ). Input: Using the function generator feed a 10 Hz sin wave and 0.5 Vp-p into Tp 1 (Section A). Output: Is taken from Tp 6 using the digital scope. a. Set the mode switch in section A to the DIFF position. b. Remove the alligator lead from the Tp 2 input. c. Calculate the differential gain for amplifiers A 2, A 3 and A 4.

9 A diff V V TP 6 V TP 3 TP 2 Tp 6 =.. A diff =.. 4. Common Mode Rejection Ratio CMRR. Input: Using the function generator feed a 10 Hz sin wave and 5 Vp-p into Tp 1 (Section A). Output: Is taken from Tp6 using the digital scope. a. Set the mode switch in section A to the COMM position. b. Measure the p-p signal voltages at: Tp 2 Tp 3 Tp 6. c. Calculate the common mode gain (A cm ). A comm V V TP 6 V TP 2 TP 3 A cm = (Must be << 1) d. Calculate the CMRR.. 5. Frequency Response of the differential Amplifier (Section B): Input: Using the function generator feed a 2 Vp-p and sin wave into Tp1. Output: Is taken from Tp6 using the digital Scope. a. Set the mode switch in section A to the DIFF position. b. Gradually increase the generator's frequency from a starting frequency of 2 Hz. c. Observe the frequency at which the amplifier's output (Tp6) reaches a maximum. Maximum Voltage at Tp6 =..

10 d. Calculate the cutoff voltage (-3dB point), V (cutoff) = * Tp6 (max) V (cutoff) =.. c. Continue to increase the generator's frequency until the amplifier's output decreases to V (cutoff); this frequency is called the upper cutoff frequency or high frequency roll- off. High frequency roll- off =

11 EXP#2: Optoelectronic Component Theory; In medical instrumentation, patient safety is a major consideration. When taking an ECG, the right leg may be common to earth ground on some medical recorders. If a line voltage come in contact with a hand, arm or part of the body, a current flow through the body takes place. Less than 1mA of current through the heart is sufficient to cause fibrillation. If, however, the patient is totally isolated from ground, the potential shock hazard is greatly reduced Patient isolation is a very important stage in biomedical instrumentation. An isolation stage is a stage that provides ohmic isolation between the input and the output of that stage. The method of coupling may be magnetic, optical, and capacitive or any means other than direct ohmic coupling. This allows the input circuit to be referenced separately and independent (floating ground) of the output circuitry (actual ground). It should be noted that there must be two isolations in biomedical instrumentation that are direct contact with the patients, one is the power supply isolation, and the other is the signal isolation. In this experiment, we are dealing with the signal isolation using optocoupler. Optical coupling The optocoupler is often used to isolate two circuits, which normally share a common ground to reduce potential equipment shock hazards to a patient. The Optocoupler (Section C) contains a light source (LED) and a sensor. The sensor can be a photodiode, phototransistor, or photo Darlington. In this form, only light waves representing the signal. Isolation and control are achieved by three-step process: 1. LED converts an electrical signal to light energy. 2. The optical signal is then converted back into electrical energy by a photo sensor (Darlington). 3. An amplifier is excited by the reconstituted signal. The high gain capability of the Darlington reduces the need for another stage of amplification. The 5Kohms potentiometer (R15 located in Section B) adjusts the signal level to the optocoupler stage; the light level in the LED is set by the DC current flow through transistor Q1. The output signal from amplifier A4 (Section B) amplitude modulates the light intensity of the LED in the optocoupler. The Darlington transistor sensor also receives light changes, which are further amplified by the high gain cascaded transistor circuit.

12 The important parameters for most optocouplers are their transfer efficiency, measured in terms of the current transfer ratio (CTR), the output transistor's maximum collector-emitter voltage rating VCE(max), the input LED's maximum current rating IF (max), and the optocoupler's bandwidth. CTR is the ratio between a current change in the output detector and the current change in the input LED that produces it. Typical values for CTR range from 10% to 50% for optocouplers with a phototransistor and up to 2000% for those with a Darlington transistor pair in the output. The gain of optocoupler, which uses a Darlington sensor, ranges from 5 to over 75. ***************************************************************** Objectives: Optocoupler parameters measurement; 1. The current transfer ratio (CTR) 2. The frequency response Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM Experimental Procedure: The Current transfer ratio CTR: DC CTR 1. Consider the optocoupler circuit section C. 2. Adjust RI7 for a voltage drop of 0.11v across R18. AC CTR 3. Measure the voltage drop across R Adjust RI7 for voltage drop of 1V across it. 5. Measure the voltages across R18 &R19. Frequency response: 1. Set the source switch to DIFF. 2. Set the sensitivity control to its max. 3. Open switches Al, A2, A3 and A4.

13 4. Feed a 30Hz sine wave into the input section A to adjust the voltage at TP6 to 2Vp-p. 5. Measure the voltage at TP7. 6. Decrease the generator frequency to obtain times the voltage of TP7 at step 10, record the frequency, (3dB point). 7. Close A4, which places C9 in parallel with C 10, repeat step Determine the upper cut-off frequency by increasing the generator frequency until you obtain times the voltage at step Close A1, what is the upper cut-off frequency? 10. Close A2, what is the upper cut-off frequency? Calculations: Compute the current inr18 (LED forward current I f, step2. Compute the current in R19 (I C ) step3. Calculate CTR dc Calculate I f and I c, step5. C T R = d c I I c f Calculate CTRac: C T R = ac I I c f

14 EXP#3: Band-pass, Notch and other filter Theory; Often, real world signals of interest are mixed with undesirable noise signals (power line interference in ECG signals etc.). Circuits such as filters are used to attenuate the amplitudes of the signals, which are not desirable. Depending on the frequencies that are desirable, filters can be low-pass, high-pass, band-pass or notch filters. The principle of action of ideal filters is shown in Figure#1: Circuits made with real-world components cannot achieve the sharp cut-off characteristics of the ideal filters shown above, but with some degree of approximation, we can get fairly close. Filters are essential in circuits such as ECG monitors where a considerable degree of interference is picked up because of the surrounding electrical equipment as well as the movements of the patient. Another area in which filters could be used is in hearing aids. The frequency at which the output voltage (V out ) equals x V in is referred to as the high- or low- frequency roll-off point. This point is also defined as the frequency at which the output voltage has dropped by 3 db (decibels). This point can be described as follows: Vout V in Voltage gains or losses, in db, are given by;

15 G V out 20 log db V in So the value of G at the roll-off frequency = 20 log (0.707). Therefore, G = -3 db, the negative sign indicates that V out was less than V in The difference in frequencies at the -3 db roll-off points at the high and low ends of a response curve is called the bandwidth of a filter. The term bandwidth usually applies to band-pass and band- rejection (notch) filters. Band-Pass and Band- Stop Notch Filters A band-pass filter passes all signals that fall within a band defined by a lower und an upper frequency limit. It attenuates all other frequencies outside of this specified band. The bandwidth (BW) is defined as the difference between the upper cut-off frequency and the lower cut-off frequency as shown in Equation BW f u f L The frequency about which the pass band is centered is called the center frequency. It is defined as the geometric mean of the two cut-off frequencies as shown in Equation: f o f L f u The sharpness of the response in the band-pass is measured by a quantity called Q. The Q of a filter, or of any tuned circuit, is the ratio of the center frequency to the bandwidth (BW). This expression is shown in Equation Q fo BW Another quantity, called the damping factor (DF), is defined as 1 divided by Q as shown in Equation DF 1 Q

16 This damping factor is important in defining the kind of response in the pass band and the shape of the roll-off curve. The instrumentation amplifier shown in Section B of the panel is also a bandpass filter, the high frequency roll off is caused by the following capacitors: 1. Feed-Back capacitors connected form an output to an input: C 39, C 3 and C Stray Capacitors connected form an output or an input to ground, C 5 and C 7. C4 and C5 are controlled by switch A1 and A2 respectively, for example when switch A 1 is closed (ON), C 4 is connected to Tp 6 through R 13.and when it is open (off), C 4 in not connected to Tp 6. The low frequency roll off is caused by the coupling capacitors connected in series with the input or with the output: C 1, C 2, C 9 and C 10, also C 9 and C 10 are controlled by switch A 4. Switch A 3 is used to control the amplitude of the signal at TP 6.1 as follows: 1. When A3 is ON, Tp 6.1 = approx Tp When it is OFF, Tp6.1 = R 15 Tp 6 R 13 R 15 R 14 The notch filter is also known as a band-stop, band- reject, or bandelimination filter. In effect, a notch filter performs in exactly the opposite way from a band-pass filter. The notch filter rejects or attenuates all frequencies inside its response curve between the 3 db points and passes all other frequencies. The bandwidth is defined as the difference in the frequencies at which the response is 3 db down. These filters are often used to reduce 50 or 60 Hz signals in sensitive medical instruments such as EEGs and ECGs.

17 State Variable filters: A state-variable filter is widely used for band-pass application. The filter consists of a summing amplifier followed by two operational amplifier integrators as shown in Figure #3. The RC circuit in both integrators sets the center frequency of the band-pass filter. The cut-off frequencies of the filters are usually made equal to one another, thus setting the center frequency of the band-pass. Notice that low-pass, band-pass and high pass outputs are all available from the same circuit. Section F of the panel shows a circuit for an active band-pass filter, which is tunable from 8-14 Hz; this filter is used in the EEG instrument (alpha waves). ************************************************************ Objectives: At the end of this experiment, students will: Understand the characteristics of active and passive filters. Understand and study the function and use of active notch filter Measure the frequency response of the state variable and notch filters (Bandwidth and gain).

18 Evaluate the operating characteristics of a state variable active filter. Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM Experimental Procedure: I. Band Pass Filter. 1. Effect of capacitors on frequency Response of the differential Amplifier (Section B): Switch A3 is closed Input: Using the function generator feed a 2 Vp-p and sin wave into Tp1. Output: Is taken from Tp6.1 when both switches A1 and A2 are closed a. Set the mode switch in section A to the DIFF position. b. Gradually increase the generator's frequency from a starting frequency of 2 Hz. c. Observe the frequency at which the amplifier's output (Tp6.1) reaches a maximum. Maximum Voltage at Tp6.1 =.. d. Calculate the cutoff voltage (-3dB point), V (cutoff) = * Tp6.1 (max) V (cutoff) =.. c. Continue to increase the generator's frequency until the amplifier's output decreases to V (cutoff); this frequency is called the upper cutoff frequency or high frequency roll- off. High frequency roll- off =

19 d. Measure the high frequency roll off when both switches are open. II. Notch filter (Section E). 1. Frequency Response of the notch filter (Section E) Input: Using the function generator feed a 50 Hz sin wave and 4 Vp-p into Tp12. Output: Is taken from Tp13 using the digital Scope. a. Open switches B1 and B2. b. Adjust the potentiometers R31 and R32 for minimum sin wave output; Minimum voltage at Tp13 (at 50 Hz) =. b. Record the output voltage at 20Hz (below the notch frequency) and 150Hz (above the notch frequency); V out at 20Hz = V out at 150Hz =.. d. Calculate the degree of attenuation at the center of the notch in db; f. Measure and record the frequencies at points C and D; Steps: 1. Calculate the output voltages at -3dB points; V C = V D = 0.707* V out at 20Hz= 2. Beginning at 20Hz, slowly increase the generator's frequency until the output voltage decreases to V C, Record this frequency as f C =.. 3. Beginning at 150 Hz, slowly decrease the generator's frequency until the output voltage decreases to V D,

20 Record this frequency as f D =.. g. Compute the width of the notch at its -3dB points, f = f D f C = h. Compute the voltage attenuation in db both above and below the notch,

21 EXP#4: Noise in Biomedical Amplifier Systems Theory; Noise is all the unwanted electronic signals coming in that you don t want to measure. This one we will leave to you: you have to determine how noisy your circuit is, and justify the method you use to measure noise. Remember from class that we characterize the noise characteristic of an amplifier by the Noise Figure. How can you measure the noise figure of your circuit? Noise in amplifiers can be caused both by the shot noise within active components and by the resistors connected to active components. Limiting the frequency response of the amplifier can reduce the noise levels in amplifiers. In a biomedical system, the input amplifier section is responsible for most of this noise. External and internal sources, as well as passive and active components, all contribute to this noise. Shot noise, intrinsic to solid-state device junctions, is possibly the greatest consideration. Patient electrodes also generate noise. At very low levels, the wiring of printed circuit boards and cables introduces noise through ground loops. Taking a voltage measurement between two distant points on the ground plane reveals the existence of microvolt variations. These, in turn, feed input signals to the amplifiers. (Different grounds between test instruments also introduce noise. In high-gain, low-noise amplifiers, the grounds of test instruments should be secured to a common point in order to reduce ground loops.) Power supplies, when their output impedance is not low enough (under a few ohms), are another source of noise. The noise may actually be a collection of pulses, spikes, and 50/60 or 120 Hz voltages. These voltages can usually be isolated by inserting RC filters between the power supply lines and the IC circuitry. Noise level measurements At low frequencies, the noise in biomedical amplifiers is of considerable importance. Low-frequency noise is in the range of 0.01 to I cycle. Drift voltages are also considered as noise. The range of 5-50 KHz is considered wide- band noise. When viewed on an oscilloscope, noise is measured from the peak-to- peak value. Since peaks are of various heights, noise measurements can only be approximated.

22 An amplifier with a gain of 100 might have a noise output of 400 n V when its total input noise is 4 n V. In order to measure such low-level signals, a high- gain oscilloscope with low noise is required. Typical oscilloscopes will measure voltage levels as low as +10 mv /cm. In addition, they themselves generate input noise in the microvolt range. The most important noise sources in the panel and how to minimize it are summarized in Table #1 # Noise sources How to minimize it? 1 60 or 50 Hz power line Notch filter (section E) interference 2 Circuit Noise (IC's) Good Design and Good Components, BIFET amplifiers generally have low noise levels. 3 Other biopotentials, when Band-pass Filters, these measuring ECG, everything else biopotentials have creates noise like other characteristics frequencies biopotentials (EEG, EMG or EOG) (frequency response) as shown in Table #2 4 Motion artifacts (man-made Relaxed subject noise) 5 Electrode Noise High quality electrode and good contact Table #1 Signal Frequency Range (Hz) Amplitude(mV) ECG QRS complex= 1mV EMG Relaxed Muscle: Contracted Muscle: EEG Table#2

23 We can control and change the frequency range in the panel (according to the bio signal we measure) using the control switches: A 1, A 2 and A 4. ************************************************************ Objectives Upon completion of this study, which includes theory, laboratory testing, and evaluation, the student will be able to: 1. Measuring the signal to noise ration in a biomedical instrumentation amplifier 2. Measuring the BW and the effect of noise on the bandwidth, the equivalent input noise 3. Select ICs for low noise applications. Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. jumper leads. Experimental Procedures: ** Switch A 3 is closed in all steps of this experiment. ** I. Measuring the output noise voltage (N out ): Input: Use jumper leads to ground test points Tp 2 and Tp 3 so that there is no input signal. Output: From Tp 6.1 in all steps. a. Measure and record the N out with: 1. Both A 1 and A 2 open 2. A 1 closed and A 2 open 3. A 1 open and A 2 closed

24 4. Both A 1 and A 2 closed.. II. Calculating the Input noise voltage (N in ): Steps: 1. Measuring the total gain of the differential amplifier A diff. Input: Using the function generator feed a 1V p-p,10hz and sin wave into Tp1. A diff =. 2. Compute the N in levels for each of the N out levels determined in step a using the following equation Noiseinput Noiseout Gain 1. Both A 1 and A 2 open 2. A 1 closed and A 2 open 3. A 1 open and A 2 closed 4. Both A 1 and A 2 closed. III. Measuring the signal to noise ratio (S / N) Input: Using the function generator feed a 1mV p-p differential signal at Tp 2 and Tp 3, 10Hz and sin wave into Tp1. With Both A 1 and A 2 closed, Measure: 1. The signal voltage (S):. 2. The N out voltage (N):. 3. Calculate the S / N. VI Measuring the frequency response of an opto-coupled instrument amplifier and the output amplifier(section G):. Input: Using the function generator feed a 1mV p-p differential signal at Tp 2 and Tp 3, and sin wave into Tp1. Output: From Tp 15 using the digital scope. *Close A 1, A 3, B 1 and B 3.

25 *Open A 2, A 4, B 2 and B Measure and record the upper cutoff frequency (upper 3db response): a. Maximum V out = b. Cutoff voltage (V cutoff ) = c. F H =

26 . Theory; EXP#5: The Electrocardiograph Recording (ECG) Electrical activity of the heart can be approximated by a dipole (a vector drawn between two opposite electrical charges) with time varying amplitude and orientation. For this simplified model, we will represent the cardiac dipole vector with M. If two electrical leads are connected to human body at two different locations, we can draw another vector in space, a, from one of the electrodes to the other. Electrical voltage observed between these two electrodes is given by the dot product of these two vectors. A plot of the electrical potential developed in the heart is called an electrocardiogram (ECG). The ECG graphically depicts the amplitude and timing of this potential as it transits the conduction system. Figure 5-1 shows a typical ECG tracing. Note that the various peaks and valleys, called waves, are labeled with letters. Taken together, these waves characterize the sequence of events that comprise the cardiac electrical cycle. The P wave is generated when the SA node develops its initial potential. Signal transit through the atria to the AV node is indicated by the P-Q interval. The R wave, often called the QRS complex, is generated as this potential is conducted through the Bundles of His, the Purkinje system, and the ventricles. Repolarization, in preparation for the next stimulus, generates the T wave. Deviations in amplitude, timing, and polarity of the various EKG waves all indicate conduction abnormalities.

27 There are many different configurations to place the ECG electrodes on a patient. Three common ones are listed below in Table 1 Lead 1 + LA - RA Lead 2 + LL - RA Lead 3 + LL LA Table 1 ECG Lead configurations. Short hand notation used in Table#1 is explained in Table# 2 below: LA LL RA RL Left Arm Left Leg Right Arm Right Leg Table 2. Short hand notations used in ECG descriptions. An ECG Amplifier The circuit diagram of sections B show the ECG amplifier. Bio-potential signals are very weak signals. Even the strongest ECG signal has a magnitude of less than 10 mv. Furthermore, ECG signals have very low drive, i.e. source has very high output impedance. Therefore, an ECG amplifier is usually required to have the following properties: 1. Capability to sense low amplitude signals in the range of mv, 2. Very high input impedance, usually more than 5 Mega-Ohms, 3. Very low input leakage current, 1 micro-amps or below, 4. Flat frequency response of Hz, 5. A high common mode rejection ratio (CMRR). Input leakage current is defined as the current an amplifier sends to the unit (human body in our case) connected to its input terminals. A high CMMR is essential since the capacitive coupling from the external electrical sources such as power lines would create a strong common mode

28 signal in comparison to the differential ECG signal. A high CMMR would mean that the A D is much larger than A C, and the differential amplification of ECG signal in the order of 1 milli-volt would be possible in the presence of common 50/60 Hz signal coupled from the power mains, which would be in the order of tens of Volts. Figure#2 below shows the typical situation in electrical biopotential amplification. ***************************************************************************** Objectives 1. Learn the sources of bio-potentials in the human body and understand the techniques used for measurement of these electrical potentials. 2. Record the ECG from the simulator. 3. record the ECG for human subject 4. Study the effects of the artifices. Material Required: 1. Insertion Panel. 2. Patient Lead Cables. 3. ECG Electrode (4). 4. PKg.of alcohol-treated Gauze Pads. 5. Lead Selector Box. 6. ECG Simulator. 7. Scope and DMM. Experimental Procedures:

29 I. ECG simulated test: Follow the ECG system shown in Figure#3 on the SIP You should close the switches A1, A3, A4, B1 and B3. 1. On the ECG simulator, set the rate to 70bpm. Select lead II on the lead selector. 2. Display the output (TP15) by the oscilloscope 3. Plot your output. and calculate the heart rate (bpm) Heart rate (bpm) = 60/T Where T is the time in seconds between two adjacent R waves. 4. Fill Table #3: 5. Repeat step 6 for lead I and lead III. 6. On the ECG simulator, set the rate to 100bpm. Repeat 5 and 6. Portion Amplitude (V) Width (sec) P P-Q QRS S ST T Two adjacent R waves Table#3 II. Recording human ECG:

30 1. Replace the ECG simulator by human subject. 2. Attach the ECG leads to the proper skin electrodes 3. Make sure that the resistance between any two electrodes< 50K,why? 4. Select lead II, plots your output, and fills the table in step 6. III. Effects of artifacts: 1. Have the human subject make a tight fist with his right hand, record your ECG. Conclude! 2. Have the subject hold his breath, record your ECG. Conclude! 3. Slide the RA electrode to an adjacent position not properly prepared with electrolyte, record your ECG. Conclude! Circuit Evaluation: 1. If the gain of the differential amplifier (section B) = 358.calculate the amplitude of the R and T waves generated by the ECG simulator. 2. Measure the gain of the output amplifier. 3. What does a double beat mean? 4. Calculate the input voltage to an ECG amplifier, assuming: 1. The input impedance of the amplifier = 100Kohms. 2. Each electrode's contact to the skin is 5Kohms.

31 EXP#6: I. Analog to Pulse Shaping II. Visual and Sound Pulse Indicators Theory; I. Analog to Pulse Shaping: The system of counting events such as pulse rate, respiratory rate, etc. requires that an analog signal be converted into pulsed events and displayed on a meter or recorder. In other words, analog signals must be timed and counted, events must be marked and or pulse periods must be indicated. To accomplish this, a portion of an analog signal is used to trigger a pulse-forming circuit. The amplitude, polarity, or rise time of a specific signal voltage is chosen as the trigger to activate an event marker. Figure # 1 below shows the sequence that leads to a pulse count including the changes in the wave shape of the signal. 1. Pulse Amplifier (section D): Amplify the signal.

32 2. Polarity correction Circuit (Section I): Clip off a portion of the signal to use its rise or fall time(r wave) to trigger the pulse stretcher circuit. In other words, this circuit removes P and T waves from the ECG complex to produce the trigger voltage(r wave) as shown in Figure # 1. This polarity correcting circuit also makes use of the R wave as a trigger regardless of its polarity, it produces a pulse when it receives either a positive or a negative going input signal, and lead reversal is then no longer a problem. If the R wave would appear inverted at the pulse stretcher input, and if there were no polarity correcting circuit, the patient leads would have to be reversed. 3. Pulse stretching circuit: Converts the modified signal (R wave) into a rectangular pulse and stretches it's duration (pulse width). The rectangular pulse must have constant amplitude and pulse width, it could be obtained from a Schmitt trigger or monostable oscillator. Each of these circuits produces fixed amplitude and fixed pulse width pulses. The IC 74LS132 is a quad Schmitt trigger,as shown in Figure# 2. One of them used as a pulse stretcher which produces a positive pulse for each R wave, R53 and C31 set the on period (pulse width) of the pulse. II. Visual and sound pulse indicators: Most monitoring equipment incorporates in its design both a visual and a sound indicators. Which are used to verify that either an event has just taken place or is currently in progress. The visual indicator (LED, D18) is controlled by the pulse produced by the Schmitt trigger (pin 3 of 74LS132). The pulse width is approximately 0.1 second. Though shorter pulse durations could be used, 0.1 second is a reasonable time when both

33 visual and audio indicators are involved. Each time the Schmitt trigger is pulsed, the light flashes. The other two NAND gates of the IC74LS132 shown in Figure#2 are used as a pulse tone(schmitt trigger) Oscillator. The IC, however, is not a power device and an audio amplifier would be needed as a follow up for driving a speaker (audio indicator).this circuit (audio amplifier) is already wired in the master builder and power supply base. The frequency of the audio pulses (Tp 19 ) generated by the oscillator is controlled by R57 and C33 using the following equation: f R C 33 Tone generator circuit can be formed by using a dual timer (556). One side of the IC, used as a monostable oscillator, sets the pulse period, while the second side, operating as an astable oscillator, produces the tone. 4. For monitoring, average the pulse count with a low pass filter amplifier (Integrator) and apply the averaged voltage to a DC meter. This will be discussed in details in Exp#7. ************************************************************ Objectives: 1. Utilize a Schmitt trigger circuit for controlling other circuits. 2. Study an indicator circuits, which utilizes a pulsed LED and a loudspeaker. Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. Jumper leads Experimental Procedures:

34 Input: Using the function generator feed a 0.5V p-p, 1Hz and square wave into Tp10 (section D). 1. Observe and record the wave shapes at the following test points: a. Tp11: b. Tp16, Tp17 and Tp18 (Explain the wave shapes)? c. Output of the pulse stretcher (pin 3 of 74LS132 IC); what are the width and the period of the pulses? *Width =.. *Period = d. Tp19 *What is the period of the pulses? Period =.. e. Tp20: (explain the wave shape)? 2. Compare the pulse width at pin 3 with the length of the total oscillation period, Are they the same? 3. Caculations: 1. Form the previous measurements; calculate the frequency of the following: *Audio pulses (Oscillation):. *Input signal (function generator):. 2. What is the purpose of the following? * R53 and C31 (section J):

35 *R57 and C33 (section K): *R71 (section K):. 3. If you vary the function generator repetition rate, does the frequency of the following pulses vary? *Audio pulses (Oscillation) Tp19:. * pin3:. 4. What is the main function of? * Transistor Q2? * Transistor Q3?

36 EXP#7: Rate Meters Theory; The rate metering circuit converts varying pulses into stable pulses whose amplitude and width are fixed and its frequency is variable as explained in the previouse experiment. Rate meters operate by averaging or by measuring the time between pulses. The averaging method (see section L in the insertion panel) changes the varying frequency of the signal into an average DC level; this DC voltage can derive an electromagnetic meter. The output pulses from the pulse stretcher circuit with constant amplitude and width are averaged per time using the double integrator circuit shown in section L of the panel,the wave shape of the output signal at Tp 22 is triangular with a negative DC level. The double integrator requires 6 to 8 pulses (beats or R waves) for the meter to reach its averaging level, while the single integrator(one capactor in the feedback) requires 15 to 18 pulses. The averaging method of rate counting is one of two techniques used. The second method is pulse-to-pulse counting method: the period between pulses is counted with a frequency meter. This method will be explained in detailes in exp#8. ************************************************************ Objectives 1. Study how the rate of a periodic signal can be counted 2. Study the double integrator circuit. Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. jumper leads

37 Experimental Procedures: Input: Using the function generator feed a 1Hz and positive pulses into Tp18.1 (section J). 1. First start with no input pulses. What is the DC voltage output of the integrator (Tp22)?.. The meter reads 2. With 1 Hz input pulses, adjust R65 for suitable BPM. Measure the frequency and period of pulses at Tp22. Frequency (Hz) = Period (ms) = 3. Check the calibration linearity of the meter at 50 bpm and at 60 bpm. The period of pulses at 50bpm =.. The period of pulses at 60bpm =.. Is the meter calibration linear? What is the estimated percentage of deviation at 60bpm and at 50bpm? *At 60bpm: *At 50bpm: *Does the percent of deviation increase or decrease with rate? Observe and record the wave shape at Tp22 and measure the DC voltage output. 6. Draw on the same graph the wave shape of the signals at the input of integrator/metering circuit and at Tp22.

38 Questions: 1. In any system of counting events (such as heart rate) analog signals must be converted into pulses, the sequence leading to a pulse count by the averaging method is as follows: a. Amplify the originating signal. b. Clip off a portion of the signal voltage, what is the purpose of this step?...and Which circuit in the panel you studied represents this step?...,draw the wave shape of the output signal of this circuit.. c. Use a modified signal to produce constant amplitude and constant width pulses, which section in the panel represents this step?... and why we need constant width pulses?... d. Average the pulse count with a low pass filter and apply the averaged voltage to a DC meter, What is the main function of : R65 (section L)?... D19 and D13 (section L)?... C35 and D12(section L)?...

39 EXP#8: I. Pulse Rate Digital Meters II. Pulse Rate by Photoplethysmography Theory; I. Pulse Rate Digital Meters: During pulse rate counting by means of averaging, individual pulses cannot be observed. A change in rate is scarcely perceptible because the meter fluctuates about an average value. Extra beats and/ or dropped beats are, therefore, not easily detected. A more accurate procedure in observing such rapid changes would entail measuring the time between the beginning of one pulse and the beginning of the next pulse. The pulse rate (F) is obtained from the pulse period (T) as Where: f 60 T F= pulse rate in beats per minute (bpm), and T= time in seconds. General block diagram of the Pulse Rate digital meter shown in sections M O P in the panel using the function generator is shown below: Tp 1 amplifiers D 1, D 2 and D 3 (Section M)) Comparator D 4 P.L.L (Section O) Frequency counter (Section P). The Frequency Synthesizer (section O) Most frequency meters cannot register frequency rates below 10 Hz. To measure low frequencies, a phase-locked loop IC that can provide frequency multiplication is used as a frequency synthesizer. The PLL, performing as a synthesizer, tracks the incoming signal with respect to time. Figure #1 shows the block diagram of a synthesizer used in the panel, which incorporates a frequency divider.

40 The phase comparator functions as a mixer whose difference frequency is first filtered by a low-pass filter, then amplified and used to synchronize the VCO. The VCO oscillator can operate at 60, 600 or 6000 Hz, or at much higher frequencies. For the panel, the VCO operates at 600Hz. The oscillator frequency determines the divider requirements. The divider can be formed using one, two or three IC's, depending on the availability of components. For the panel, we have three dividers providing divide by 10, 6 and 10 respectively as shown in Figure# 1. Pulses applied to pin 14 of phase comparator (Tp4) are compared with the output of the VCO after it has been divided by 600 (Tp11). Any difference in frequency or phase between inputs 14 and 3 of the phase comparator appears as an error voltage at pin 13. After filtering by R44, R45 and C12, this error voltage appears at the input of the VCO (pin 9). It is of a proper magnitude and polarity to drive the VCO toward that frequency which will produce phase and frequency coherence at the phase comparator input. The VCO frequency range is determined by R47, R48 and C 13. For the component values shown, this particular VCO ranges from 60 Hz to 2,200 Hz per second.

41 The filter component values were selected to provide a good capture range as well as good damping characteristics. The circuit, as shown, will capture and lock onto any frequency within the range of the VCO in under 5 seconds. If a pulse train having a rate of 1.25 Hz per second is applied to the input of the phase comparator, the output frequency of the VCO will adjust to 750 Hz (600*1.25) per second within 5 seconds after the input signal has been applied. The Frequency Counter Section P in the insertion panel shows the circuit of a frequency counter. The circuit can count low-frequency rates from bpm. The frequency from the PLL (TP8) is applied to pin 12 of U4. Within U4, there are three cascaded decimal counters, each of which has a binary coded decimal output. The three counters, which are multiplexed, appear on the four output lines of U4 (at pins 5, 6, 7 and 9). These four outputs, called the data lines, are applied to a decoder and driver, U5. The binary coded decimal output from U4 is decoded by U5, and appears as a seven-segment display signal at pins 13, 12, 11, 10, 9, 15, and 14. The displays are activated in a commutative manner from the digital select outputs of U4 and fed to transistors Q1, Q2 and Q3. The most significant digit (UIO) has a special logic added by U6 and U7. These ICs blank a zero number in the most significant place. For all numbers between zero and 99, the 0 is blanked at the MSB. When the frequency goes over 100, the most significant bit display is enabled and will be read as 1, 2, 3 or whatever frequency might be present. The three 8-segment displays do not require a heavy-duty power supply, since the LED segments are multiplexed at a 500 Hz rate with a 12% duty cycle. While the circuit application is for low-frequency counting, the same IC's can read frequencies of 100 MHz. Reference is made to the Appendix for additional technical data on each IC and application notes. Objectives 1. Describe how a phase locked loop (PLL) circuit can be used for frequency multiplication. 2. Evaluate the operation of a PLL based pulse rate counter. 3. Evaluate the operation of a digital counter and LED seven-segment display.

42 Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. Experimental Procedures: 1. Consider the pulse rate metering circuit consists of section M,O and P in SIP kit 2. Using function generator, feed 1Hz, 1vp-p and sin wave into Tp1 3. Set the two Rate/Temp switches to rate position. And increase the sensitivity until the digital meter shows a steady pulse rate. 4. Display the output at TP4 by using oscilloscope. Plot it 5. What is the function of D4?.. 6. Record the pulse period and then compute the pulse rate from the period 7. Record the frequency of output at TP8, TP9, TP10 and TP Is the frequency at TP11 equal to the pulse rate at TP4? Explain.. 9. The first section of ICM14566B provides a division by.between TP8 and TP9. This is followed by a division by..between TP9 and TP The second section of ICM14566B provides a division by The phase comparator located in U compares two frequencies, what are these frequencies? 12. If the frequency at TP11= 1.25Hz, calculate the frequencies at Tp8, Tp9, Tp10 and Tp21 in Hz. 13. With no input, the frequency meter reads 4 or 5 BPM, Explain?

43 II.Pulse Rate by Photoplethysmograph: Theory; The photoplethysmograph measures transmittance of light through a capillary bed in order to determine pulse rate. A light source (e.g. LED) transmits light through a capillary bed (e.g finger tip or ear lobe) and photodetectors (e.g. phototransistor) are placed appropriately to measure the reflected and/or transmitted light. It can also be used to measure blood flow rate, though this measurement is extremely sensitive to motion artifact. With each beat of the heart, arterial blood pressure rises (systole period) and the extremities increase: (slightly) in physical size. In addition, increased oxygenation decreases the optical density of surface tissue. During the heart's period of relaxation (diastole period), the pressure falls; density in- creases, and the extremities decrease in physical size. Since these cyclical changes follow the cardiac cycle, they can be used to determine the peripheral pulse rate. Measuring pulse rate by counting periodic fluctuations in some physical parameter is called plethysmography. The photoplethysmograp monitor consists of light source (LED), Photo sensor (photo resistor R 5 ) and the processing circuit described in Part. I of the experiment (sections M-O-P). The amplifier, with its law-frequency bandpass, has a frequency response of 1 to 20 Hz and a gain of approximately2, 000. The optical sensor can be a photoresistor, photo- diode, or phototransistor. The physical placement of the components and the method of holding the probe in place present a greater problem than the electronic circuitry. The Figure shows the light source and. The finger fully covers both components so that the light must pass through the tissue and the sensor.

44 Several problems occur in making this type of measurement 1. When cold air or water contacts the finger's tissue, the vessels contract, blood flow is decreased, and sensitivity is diminished. Therefore, fingers should always be kept warm. 2. If the probe holding the optical devices presses too firmly, the vessels are constricted, blood circulation is reduced, and sensitivity falls off. 3. The physical placement of the LED and sensor is very important. Light should not spill over and bypass the finger The next figure shows a sketch of the pulse wave shape as recorded on the strip chart recorder. The systolic peak is used to trigger a comparator or Schmitt trigger circuit for rate counting. The mean resting blood pressure varies between individuals; 80 mm of mercury is typical. The term used for the static pressure is diastolic pressure. When the aortic pressure reaches its peak, it is referred to as systolic pressure: the graph shows this pressure as 130 mm Hg. The ratio 130 / 80 describes the person's arterial blood pressure. When pressure falls as a result of the closing of the heart's aortic valve, a dip (called a dicrotic notch) takes place. ************************************************************ Objectives: 1. Explain how the peripheral pulse is recorded from a finger.

45 2. Observe some of the effects of breathing and exercising on pulse rate. 3. Observe the effects of temperature on pulse rate measurement Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. Photoplethysmograp sensor. Experimental Procedure: 1. Consider the circuit in section M (SIP385-2) 2. Attach the light sensor to the right forefinger, taking care not to make too tight a fit. The light source and cell should be facing the palm side of the finger. The transducer should fit firmly, but should not constrict blood flow. Connect the cable to the panel by inserting the plug into the pulse rate jack. Relax your arm on your lap, on the arm rest of a chair. The forearm should not be above the level of the heart. 3. Set the two toggle switches (Sections 0 and P) to the rate position. Connect an oscilloscope to the output jack (Section M). Increase the sensitivity until the rate meter shows a steady pulse rate. Record your pulse rate. 4. Confirm that the pulse rate stops when the blood flow stops. Occlude (stop by closing) the blood flow by tightly squeezing the lower half of the finger being tested between the sensor and the knuckle. After a few moments, release the occlusion. What happens to the pulse rate during and just after occlusion? 5. Stand in place with the pulse sensor attached to the finger. Your arm should be extended down by your side for at least one minute. Record your pulse rate: _ bpm. Adjust the sensitivity control as necessary. You will compare this normal beat with your pulse rate after exercising. 6. Turn the sensitivity control to zero after noting the initial setting. Run in place for one or two minutes so that your heart establishes a rapid beat. Stop running and increase the sensitivity control to the original setting. Record your new pulse rate. Is the pulse rate faster?

46 7. After your pulse has returned to its normal rate, breathe heavily for a while and observe how heavy breathing affects your pulse rate.. 8. Hold your breath for at least seconds and note the effects on your pulse rate. a. Stand in position with your hand by your side. Record your pulse rate. Slowly raise your transducer-attached arm, outstretched, until it is b. level with your heart. Record your pulse rate and note any required changes necessary in the sensitivity control setting. c. Raise the arm fully above your head and hold it in position while recording your pulse rate. If the pulse disappears, slowly lower the arm and determine in what position the pulse reappears. Describe the effects. 9. Attach the probe to a finger of the right hand. Record the pulse rate. When recorded, dip the left hand in cold water. Dry the hand and transfer the probe to the left hand; then record the pulse on a cold finger. Dip the right hand in very warm water, dry it, and then record pulse rate. 10. What do you think happens to a person's pulse rate and blood circulation? when the body has been exposed to extremely cold temperature? 11. What effect do you think smoking has on the pulse rate? (Ask a doctor to describe the effects of smoking on blood circulation and breathing.) 12. Record the static DC voltages for MC 3403 (pins 1-14) when the Sensitivity Control is set to zero. (See Section M of SIP385-2). 13. Set the Sensitivity Control to Maximum (fully CW). Feed a function generator (25Hz, sin wave and minimum output of the generator you have) into TPl. Connect the oscilloscope to TP3. Record the voltage level on TP Find the voltage level on TP 1. Determine the gain of the circuit.

47 15. What is the frequency response between the 3 db points? 16. What is the purpose of D 1 and D2? 17. Which resistors establish the voltage reference of the comparator?..

48 EXP#9: Galvanic Skin Resistance (GSR) Theory; The skin exhibits a resistance to the flow of an applied external current. This resistance, which is normally in the range of 100,000 to 1,000,000 ohms, decreases in response during periods of emotional stress. Resistance changes are particularly notice- able on the palms of the hands and soles of the feet. In addition, the surface of the skin exhibits an electrical potential. This potential, which may range as high as 50 m V, is also influenced by emotional states. Both the Galvanic Skin Resistance (GSR) and the Galvanic Skin Potential (GSP) can be used to indicate the level of emotional response to a stimulus. Fluctuations in these skin measurements are referred to as psychogalvanic reflexes. Galvanic Skin Resistance (GSR) The GSR is obtained by passing a small constant current (less than 20 A) through skin tissue. Electrode sites are chosen on areas of high concentrations of sweat glands. When sweat glands are stimulated as a result of some stress they secrete a conducting fluid. This increased fluid content lowers the skin's resistance. Since the GSR changes by less than 1/2 of 1percent of its initial value, a high gain amplifier is necessary where G = 1000 or more. In addition, a low-pass input filter ( Hz) is needed to remove extraneous biopotentials and other artifacts. As with the ECG measurements, the test results are adversely affected by a high electrode contact resistance. Galvanic Skin Resistance (GSP) The GSP consists of both a DC potential and a slowly changing AC component. The signal voltage may be as much as 50 m V, with an evoked response. Design requirements for GSP monitors include a high-gain amplifier and a low-pass filter. No constant current source is necessary for GSP measurements. General Block Diagram of GSR monitor: DC current source (pnp Transistor) GSR Electrodes Amplifiers (f1 and f2) LM3914.visual Indicators (10 LED's) 566 Tp17 Audio amplifier Loud Speaker

49 The GSR monitor uses a DC current source passed through a changing skin tissue to generate a signal voltage. Changes in skin resistance are reflected as changes in signal voltage. The signal is amplified and then fed to a light display and tone generator. The greater the evoked response, the higher pitched is the tone and the greater the number of lights which turn on. Section S: Light Bar indicator: This display consists of IC LM3914 (consists of ten comparators), which converts variations in amplitude of the analog signal into ten voltage steps. Each step controls a voltage comparator circuit, which in turn illuminates an LED. The light bar responds to each GSR response. The greater the response, the larger the number of lights which will turn on. Section R: Glide Tone Circuit. The glide tone is produced by a 566 oscillator whose output is either a square wave or a triangular wave. The frequency of oscillation is determined by the value of C 22 and R 71 to R 80. A DC voltage change on pin 6 of the IC will also shift the frequency of oscillation. As each LED lights on, the respective voltage to the connecting resistor goes high. The LEDs turn on sequentially, placing additional resistors in parallel. The voltage applied to pin5 steadily decreases. When the tenth LED turns on, all resistors R71 to R80 are in parallel and the tone is at its highest pitch. Frequency at pin4 (566) = 2 V RCV V C Where V C : biased voltage at Pin 5, R: between Pin 6 and V + and C: between pin7 and ground. Objectives: 1. Measuring the skin resistance 2. Describe the influence of emotional or physical stimuli 3. Learn the design of skin resistance monitot Material Required: 1. SIP Kit 2. Digital storage Oscilloscope

50 3. Function Generator 4. DMM. 5. Finger electrodes with cables. Experimental Procedure: 1. Hold one electrode in each hand, gripping the electrode between the thumb and forefinger. Read the dermal resistance on the ohmic scale using DMM. 2. Using your own saliva, wet the surface of the fingers which are in contact with the electrodes. Again measure your skin resistance. Does the resistance increase or decrease? 3. Attach the two ECG electrodes to the palm side of two fingers. Insert the GSR plug into the GSR input (section Q). Increase the control sensitivity to 2 or 4 divisions. Press the CAL (calibration) pushbutton and observe if the full light scale is reached. With each press of the test button, the top light should be reached. If it does not, increase the sensitivity setting. 4. The subject should be seated and relaxed, with eyes closed. The arm and hand and not the electrode should rest on the arm of the chair or on the lap. There should be no strain on the hand. Allow the subject to remain relaxed for at least one to two minutes. There should be a minimum of room noise. The quiet condition is part of the subject's conditioning. If responses are observed, they are being caused by the subject's cognitive process. 5. Stand behind the subject and lightly touch the subject's hair. Say nothing. Note the light bar response and rotate the sensitivity control as necessary to obtain a near full-scale deflection. Continue touching the subject in different places so that a response is evoked. Say nothing. Try clapping your hands near the subject's ear and observe the response that follows. Try touching the nose with a feather. 6. Approximately, how long is the time delay between the stimulus and the response? 7. When good responses are obtained, stimulate the cognitive process by asking stressful questions. The subject's eyes should remain closed. 8. Good responses, consistently obtained, indicate that the subject is conditioned and the eyes can now be opened. Ask the subject to look at the light bar and continue your questioning, touching, etc. in order to evoke a response.

51 9. Have the subject count backwards, in odd numbers, while the eyes are closed. Frustration can cause an emotional response. Is a response obtained? 10. In addition to the light bar as an indicator of the GSR response, the glide-tone is available. Adjust the tone volume (R67, Section R) to a comfortable level. With each rapid response, a sliding tone pulse is produced. If a tone is not produced, increase the sensitivity setting. 11. The subject should try to prevent the tone change from occurring. Again, the stress created in preventing the tone causes the response to happen. Before removing the electrodes, return the sensitivity setting to zero. Repeat the testing procedures on several subjects. Always readjust the sensitivity control and calibrate for a full-scale response. 12. Place a DMM between TP 13 and TP 12. Measure the voltage present (V1). Press the "Cal" switch (V2) and measure the difference in voltage (V1-V2). V1>V2, Why? 13. Determine the total constant current being supplied by measuring the voltage drop across R49 (39 K ),I c. 14. From I c, calculate the voltage drop across R50 (470 ) 15. Measure the DC voltage required at TP15 to obtain a full light bar swing. 16. The voltage at pin1, TP 18 (LM3914) of the comparator is a collector. Record the voltage at TP18 before (V1) and immediately after pressing the "CAL" button (V2).V1>V2, Why? 17. Use a frequency counter or oscilloscope to determine the frequency range of the tone change. ( Low and high frequencies.) *Low frequency (all LED's are OFF)= Calculate the theoretical value of this frequency?. *High frequency (all LED's are ON) = Can you replace the 566 with a 555timer (a stable)? And why?

52 EXP#10: Temperature Measurement Theory; In this Laboratory, the surface body temperature is going to be measured at different locations on the body. Body temperature can either be measured mechanically, with a mercury thermometer, or electrically, with a thermistor, diode probe, or a thermocouple. The mercury thermometer is slow, although accurate. Among these electronic devices, the thermistor probe has proven to be the most popular. The thermistor probe is a negative-coefficient, temperature-sensitive transducer, also referred to as NTC device. As the temperature increases, its resistance decreases. The resistance change of the thermistor is logarithmic rather than linear as shown in the equation below. In order to produce an output voltage, which is linearly related to temperature change, an amplifier with an antilog gain curve must be used. Other forms of compensation, such as Wheatstone bridge and special feedback amplifiers, have also been used. R TH R o B 1 T 1 T o Where R TH : Thermistor Resistance. R o : Resistance at temperature T o (usually 25 C) In all cases, accuracy, resolution, linearity and temperature range are important design considerations. In biomedical measurements, a resolution of 0.1 C would be desirable, although a 0.5 C resolution is quite adequate. The Diode Sensor: If a diode is forward biased, the voltage drop across the diode's junction will change at a rate of 2.24 mv/ C. I Is V D n V T 1 Where I: diode current. I S: Reverse bias saturation current. V D : Voltage across the diode. KT V T : Thermal voltage= q

53 Silicon diodes, such as the Fairchild FDH600, can be used as temperature sensors by virtue of the fact that the forward voltage across the diode is nearly a linear function of temperature as shown in the above equation. Figure # 1 shows a plotting of the diodes voltage versus temperature in degrees centigrade. General block diagram of the Temperature Digital Meter: Diode Probe amplifiers E1&E2 (Section N) PnP Transistor voltage controlled Oscillator (566) Frequency counter( Section P). Amplifiers E1 and E2 provide the necessary gain for converting a silicon diode temperature sensor into a change in potential. This voltage is observable at test points Tp5 and Tp6. The second halve of the circuit includes an LM566 as a voltage controlled oscillator(explained in Exp#9), its used to convert the voltage change into a frequency change. The diode sensor is more sensitive than a thermocouple but is somewhat less than a thermistor. Thermistor and diode probes are utilized in biomedical instrumentation. ************************************************************ Objectives 1. Describe how temperature varies over the surface of the body. 2. Study the characteristics of diode sensor which used in temperature measurements. 3. Evaluate the performance of typical circuit used in temperature measurement.

54 Material Required: 1. SIP Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. Diode Probe and sheath. Experimental Procedure: I. Circuit Calibration: a) Place the C/F toggle switch in the C position. b) Place the rate/temperature switches in the temperature position. c) Insert the plug of the temp probe into the jack in section N. d) Take your oral temperature using a mercury thermometer, then take your oral temperature using sheath covered diode, adjust R 30 until the digital display reads the same as the mercury thermometer. e) Place the C/F switch in the F position and adjust R 89 to obtain the equivalent Fahrenheit temperature. F = 9/5 C f) R 88 is calibrated to read 37C when the probe is not inserted, remove the probe and adjust R 88 for a 37C reading. 1. Consider the circuit consists of section N and P in SIP kit. 2. Insert the sensor into experimental panel. 3. Set the Rate/Temp switches to temp. 4. Cover the probe with a plastic sheaths, place the covered probe under your tongue. 5. Record your oral temperature. 6. Record the surface temperature of the skin at selected sites as in Table#1... Site Temp( C o ) Forehead-frontal Forehead-temple Inside the ear canal Neck, side Right forearm Right forefinger Left forefinger Table#1

55 g) Where was the highest temperature? Where was the lowest temperature? h) Blow across the sensor and record the voltage change at T P5. i) Repeat step 8, record the voltage at T P6. j) Check the linearity relationship between a voltage change due to a temperature rise and the change in frequency at T P7 (VCO output), measure the voltage at T P6 and T P5 and measure the frequency at T P7. Temp in C V TP5 V TP6 Freq at T P7 Room Temp.. Oral Temp.. Between thumb and fore finger. Table#2 k) Plot the relation between the output voltage at T P6 and the frequency at T P7.

56 EXP#11: Respiratory Rate Theory; The respiratory system is responsible for bringing oxygen into the body and carbon dioxide from the body. Different parameters can be measured to show the performance of the human respiratory system. In evaluating the lung function, three main factors are considered: 1. Volume capacity.(usually measure by spirometer) 2. Rate of Breathing. 3. Gas Exchange. In this experiment, we are interested in the respiratory rate measurements. Different techniques can be used. In this laboratory, the nasal airflow method is used to determine the respiratory rate. A small diode temperature sensor is inserted into one nostril. The sensor tracks the temperature difference between inhalation and exhalation. This change in temperature is amplified and made to control a comparator or Schmitt trigger circuit. The resultant pulse rate can then be counted by either the meter averaging method or pulse-by-pulse methods.. General block diagram of the Respiratory Rate Digital Meter: Diode Probe (Section N) amplifier E1 (Section N) D1, D2 and D3 (Section M) D4 (Comparator) P.L.L(Section O) Frequency Counter(Section P) A temperature sensitive diode is held under one nostril. The short time constant 1 of the sensor enables the element to accurately track temperature fluctuations. The mv signal is amplified and used to fire a comparator (D4). The comparators pulse rate is converted into a frequency by the P.L.L. The frequency change feeds the frequency counting circuit, which has been previously described. Most of the circuits used here have been previously encountered. In the laboratory, an overall system is evaluated. The temperature sensor on one Time constant of a medical sensor is the time required for the sensor to reach 63.2 % of its final response. 1

57 panel (SIP 385-2) is connected to the meter rate section on the second panel (SIP 385-1). ************************************************************ Objectives: 1. Describe the basic functioning of the respiratory system. 2. Measure the respiratory rate. 3. Evaluate a respiratory recording instrument. Material Required 1. SIP Kit 2. Temperature diode sensor 3. Temperature sheaths. 4. Digital storage oscilloscope 5. DMM 6. Jumper leads. Experimental Procedure Respiratory rate measurements will require the use of both panels. The meter rate circuit is requiring since the breathing pattern is too slow (12-20 BPM) for period recording by the digital display. 1. The temperature sensor is inserted into Section N of SIP385-2 and Tp4 is connected by a jumper lead to Tp18.1 in Section J of SIP Each temperature change by exhaling causes a positive pulse at Tp4 and these breathing pulses are arranged on the rate meter. 2. Set the Rate/Temp switches to Rate. 3. Cover the probe with a plastic sheaths and Hold the sensor under or in a nostril passageway. Before taking any measurements, check that the two insertion panels are work well, in other words, the digital meter must read approximately your respiratory rate and the visual alarm LED(Section j)must be ON for each temperature change. 4. Record the output at TP4 by using oscilloscope. 5. Record your respiratory rate.

58 6. Exercise by running for one minute, and then record your respiratory rate. 7. With each breath, how many mv changes appear at TP5? 8. The digital display does not work well. Why? 9. What is the wave shape at TP4 (Section M)? 10. What is the wave shape at TP18 (Section J)?

59 EXP#12: I. Electromyograms (EMG) II. Electroencephalograms (EEG) I. Electromyograms (EMG) Theory; It is possible to record the action of skeletal muscle in the body using either strain gage sensors monitoring the displacements and forces produced by the muscle or biopotential electrodes sensing electrical activation. Direct force measurements require intimate contact between the muscle and strain gage. For body surface recordings, this presents a problem. However, the electrical activity of skeletal muscles can be recorded by applying electrodes to the skin above the muscle in question. The pattern produced by the combined action potentials of many motor units is called an electromyogram as shown in Figure#1. In this laboratory, we will restrict out experiments to biopotential surface recordings of this type. ************************************************************ Objectives: 1. Describe the action potentials of muscles as produced by the stimulation of nerves 2. record the EMG potential on the biceps and triceps muscles 3. record the EMG potential on the forehead

60 Material Required: 1. SIP Kit 2. ECG simulator 3. ECG lead selector 4. ECG paste 5. ECG leads cable 6. ECG electrodes 7. Alcohol 8. Digital storage Oscilloscope 9. DMM Experimental Procedure: 1. Consider the EMG recording system which consists of section A, B, E and G in SIP385-1 kit. 2. Close switches A3, B1 and B3. 3. Initially attach the RA and LL electrode leads to electrodes located on the inner forearm. One electrode should be near the wrist; the other about 8 inches distant on the same forearm. The electrode marked RL should be centered in the area between the other two electrodes, not touching either one. This is the common electrode, and it remains in this location during all tests. 4. Connect the Lead Selector Box plug to the jack in Section B. Set the box to the Lead II position. The mode switch is left in the OFF position. 5. connect the oscilloscope to output of the amplifier (section G) 6. The arm with the attached electrodes should be relaxed on a table. Increase the sensitivity gain control of the EMG amplifier (Section B) as necessary to obtain observable output wave shapes. The scope's base line should be flat when muscle stress does not exist. 7. Place an easily gripped object in your hand (ball of paper, rubber ball, piece of wood, etc.). Start squeezing the object and observe the base line. Adjust the sensitivity control as necessary to obtain an effective scope display. Input signal range may vary according to the subject's strength and therefore, if the grip is strong, you may wish to lower the sensitivity level. 8. Measure the spike amplitudes observed on the oscilloscope. The tone should fire at random as the object is gripped and should stop when the muscle is relaxed. 9. Check your biceps muscles. Move the electrodes RA and LL to the biceps muscles of your right arm. Clean the areas as before. Place one electrode just

61 above the elbow flex and the other about 4 inches further up. While seated in a chair, hold your right foot firmly against the floor; at the same time use your right hand to lift your right leg. Force your leg down so that your arm must work hard in trying to make the lift. 10. Feel your biceps muscle with your other hand. Also feel your triceps muscle. Which muscles are contracting and which are relaxed? Observe the display on the oscilloscope during muscle stress and note the change. 11. Check your triceps for contraction. Use the back of your hand to push your leg down to the floor. When the pressure is increased, feel your triceps and biceps muscles. Which are contracting and which are relaxed? 12. Move your electrodes over the triceps muscles (as you did for the biceps measurement) and record the contractions. Adjust the sensitivity control as necessary. 13. Reduce the sensitivity to 0. Either ECG or EEG leads can be used in this recording. Secure the electrodes. Connect electrodes RA and LL to the forehead directly above the eyebrows. Be sure to cleanse the areas. Connect the ground lead RL to the right shoulder, near the neck. 14. Increase the sensitivity if necessary. Tense the forehead muscles by frowning and record the effects. Headaches and emotional stress are recorded in this same manner. During biofeedback exercises, the forehead EMG potentials can be integrated and used to control a meter which displays a numerical value for the stress level. ************************************************************ II. Electroencephalograms (EEG) Theory; Low-amplitude (microvolt range) electrical potentials believed to be generated by large numbers of nerve cells known as pyramidal cells, located in the outer layer (cortex) of the brain, polarize and depolarize in response to various stimuli, creating the EEG waveform. These fluctuating electrical potentials are detected by electrodes placed on the scalp and are displayed and/or recorded on the EEG. Measured signal (which typically ranges from 10 to 300 mv), through a series of stages. The gain, or sensitivity, of each channel is adjustable. Userprogrammable instruments require that montages be programmed at the user s

62 facility and stored in the electroencephalograph s memory until changes are needed. The EEG signal is a composite of a range of frequencies (the 1- to 30- hertz [Hz] range usually proves the most useful) and includes electrical noise, which is inherent in low-level measurements. Typical electrode attachments sites for EEG recording are temporal, Frontal, Parietal, and occipital as shown in Figure#3.