Biomedical Instrumentation Lab 1

[Type the document subtitle]

Department of Biomedical Engineering

Biomedical Instrumentation Lab I

BME (418)

Modified by Dr.Luay Fraiwan and Eng.Ruba AL.Omari Spring 2011

2

se of ContentTabl

Page

Title

Exp#

3

Introduction

##

5

Differential Amplifiers

12 Pre-Lab #1

1

15

Optoelectronic Components

19 Pre-Lab #2

2

21

Band-Pass, Notch and other filters

28 Pre-Lab #3

3

30

Noise in Biomedical Amplifier System

35 Pre-Lab #4

4

37

The Electrocardiograph Recording (ECG)

43 Pre-Lab #5

5

45

I. Analog to Pulse Shaping. II.Visual and Sound Pulse Indicators.

52 Pre-Lab #6

6

54 Rate Meters 57 Pre-Lab #7

7

59

I. Pulse Rate digital meters. II. Pulse rate by photopllethy- smography.

68 Pre-Lab #8

8

70

Temperature Measurements

75 Pre-Lab #9

9

77

Respiratory Rate

80 Pre-Lab #10

10

82

Galvanic Skin Resistance GSR

11

87

EMG and EEG

12

95

References

##

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 show 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 milli volt 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 SIP385-2. 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 (common-mode) 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 (Adiff)] to the [common – mode gain (Acm)]. This relationship is called common mode rejection ratio (CMRR) and is expressed by equation

AcomAdiffCMRR log20

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 (Voutcm= Voutdiff). Therefore, CMRR can be determined from the input voltages as shown below:

diff

cm

VinVinCMRR

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

6

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 1012 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 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:

7

4.2925

6 RRA diff

Vin (diff) = Tp3-Tp2 = 1000

2 1Tp

Vin (cm) = Tp2+Tp3 = 12 Tp

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

The overall gain = Gain (A2, A3) Gain (A4) = 29.412.2 = 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

132

1

2221

2213

1

2624

2412

:

1000

1000

:

TpTpTpCOMM

TpRR

RTpTp

TpRR

RTpTp

DIFF

8

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 SIP385-1. 2. DMM. 3. Jumper Lead. 4. Oscilliscope. 5. Function Generator.

Experimental Procedure: 1. Balancing the Differential Amplifier (A4). Input: Using the function generator feed a 10 Hz sin wave and 1 Vp-p into Tp1 (Section A). Output: Is taken from Tp6 using the digital scope. a. Set the mode switch in section A to the COMM position. b. Adjust R10 (section B) as necessary for minimum sin wave output at Tp6. TP6 = ……………………………..

9

2. Single Ended Gain (One Input (Tp3)). Input: Using the function generator feed a 10 Hz sin wave and 1 Vp-p into Tp1 (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:

Tp4….………………………………..

Tp5…………………………………

Tp6 …………………………………

d. Calculate the single ended gain between Tp3 and Tp6.

6

s3

TP

TP

VAV

……………………………………………………………. e. Using the digital scope, connect Tp4 to channel 1 and Tp5 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)?.........................................

10

3. Differential Gain (Two inputs: Tp2 and Tp3). Input: Using the function generator feed a 10 Hz sin wave and 0.5 Vp-p into Tp1 (Section A). Output: Is taken from Tp6 using the digital scope. a. Set the mode switch in section A to the DIFF position. b. Remove the alligator lead from the Tp2 input. c. Calculate the differential gain for the instrumentation amplifier section (B).

6

3 2

TPdiff

TP TP

VAV V

Tp6 = ……………………………………….. Adiff = ……………………………………….. 4. Common Mode Rejection Ratio CMRR. Input: Using the function generator feed a 10 Hz sin wave and 5 Vp-p into Tp1 (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: Tp2…………………………

Tp3…………………………

Tp6………………………….

c. Calculate the common mode gain (Acm).

6

2 3

TPcomm

TP TP

VAV V

11

Acm = ……………………………… (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 = ……………………….. d. Calculate the cutoff voltage (-3dB point), V (cutoff) = 0.707 * 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 = ……………………………

12

Faculty of Engineering Biomedical Engineering Department

Biomedical Instrumentation Lab 1

BME 418

Exp.1 Differential Amplifier

Pre-lab

Name:

Number:

13

I. Objectives:

II. Explain the main purpose of Section (A) shown below: …………………………………………………

…………………………………………………

If Tp1 = 0.5 Vp-p, calculate the voltages at:

Switch

DIFF

COMM

Tp2

Tp3

14

III. Calculate the differential gain between Tp6 and (Tp3 – Tp2) ………………………………………………. VI. Explain the meaning of CMRR ……………………………………………… V. Draw the frequency response of the differential amplifier (Section B)

15

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.

16

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. 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 385-1 Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM

17

Experimental Procedure:

The Current transfer ratio CTR: 1. Consider the opto-coupler circuit section C, Adjust RI7 for a voltage drop of 0.11Vdc across R18. 2. Compute the current in R18 (LED forward current If1) 3. Measure the voltage drop across R19 and Compute the current in R19 (IC1: Collector Current) 4. Calculate CTR.

1

1

f

c

IICTR

5. Adjust RI7 for voltage drop of 1V across it. 6. Measure the voltages across R18 &R19 and Calculate If2 and Ic2. 7. Calculate CTR

f

c

IICTR

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.

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 0.707 times the voltage of TP7 at step 5, record the lower cut-off frequency, Flower=……….. 7. Close A4, which places C9 in parallel with C10, repeat step 6. Flower=………..

18

8. Determine the upper cut-off frequency by increasing the generator frequency until you obtain 0.707 times the voltage at step 5. FUpper=……….. 9. Close A1, what is the upper cut-off frequency? FUpper=……….. 10. Close A1&A2, what is the upper cut-off frequency? FUpper=………..

19



BME 418

Exp.2 Optoelectronic Component

Pre-lab

Name:

Number:

20

I. Objectives:

II. Explain the main purpose and the operation principle of the opto-coupler shown below:

………………………………………………….………………………………………… ………………………………………………….………………………………………… ………………………………………………….………………………………………… ………………………………………………….………………………………………… III. Define the CTR of the opto-coupler. If the voltage across 220Ω = 0.11V, and the voltage across 470 Ω = 1V, calculate the CTR. …………………………………………………. …………………………………………………. ………………………………………………….

21

inout VV 707.0

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 (Vout) equals 0.707 x Vin 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:

22

BWfQ o

uLo fff

Lu ffBW

Voltage gains or losses, in dB, are given by;

in

out

VVG log20 dB

So the value of G at the roll-off frequency = 20 log (0.707). Therefore, G = -3 dB, the negative sign indicates that Vout was less than Vin 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

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:

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

23

QDF 1

Another quantity, called the damping factor (DF), is defined as 1 divided by Q as shown in Equation

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 band-pass filter, the high frequency roll off is caused by the following capacitors: 1. Feed-Back capacitors connected form an output to an input: C39, C3 and C6 . 2. Stray Capacitors connected form an output or an input to ground, C5 and C7. C4 and C5 are controlled by switch A1 and A2 respectively, for example when switch A1 is closed (ON), C4 is connected to Tp6 through R13.and when it is open (off), C4 in not connected to Tp6. The low frequency roll off is caused by the coupling capacitors connected in series with the input or with the output: C1, C2, C9 and C10, also C9 and C10 are controlled by switch A4. Switch A3 is used to control the amplitude of the signal at TP6.1 as follows: 1. When A3 is ON, Tp6.1= approx Tp6.

2. When it is OFF, Tp6.1 = 141315

156

RRRRTp

24

Notch Filter The notch filter is also known as a band-stop, band- reject, or band-elimination 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.

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.

25

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:

1. Understand the characteristics of active and passive filters. 2. Understand and study the function and use of active notch filter 3. Measure the frequency response of the state variable and notch filters (Bandwidth and gain). 4. Evaluate the operating characteristics of a state variable active filter. Material Required: 1. SIP 385-1 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): Note: Switch A3 is closed for all procedure

26

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 10 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) = 0.707 * 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 = …………………………… d. Measure the high frequency roll off when both switches A1&A2 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 (Fo) sin wave and 4 Vp-p into Tp12. Output: Is taken from Tp13 using the digital Scope. a. Open switches B1 and B2.

27

b. Adjust the potentiometers R31 and R32 for minimum sin wave output; Minimum voltage at Tp13 (at 50 Hz) = ………………………………. a. Record the output voltage at 20Hz (below the notch frequency) and 150Hz

(above the notch frequency); Vout at 20Hz = Vout at 150Hz =…. ……………………………. d. Calculate the degree of attenuation at the center of the notch in dB

(Hz

fo

VV

20

log20 );

………………………………………………………… f. Measure and record the frequencies at points C and D shown in Figure# 2; Steps: 1. Calculate the output voltages at -3dB points; VC = VD= 0.707* Vout at 20Hz= ………………… 2. Beginning at 20Hz, slowly increase the generator's frequency until the output voltage decreases to VC, Record this frequency as fC = ……………………………………….. 3. Beginning at 150 Hz, slowly decrease the generator's frequency until the output voltage decreases to VD, Record this frequency as fD = ……………………………………….. g. Compute the width of the notch at its -3dB points, ∆f = fD – fC= ……………………………… h. Compute the voltage attenuation in dB both above and below the notch,

28



BME 418

Exp.3 Band-Pass, Notch and other Filters

Pre-lab

Name:

Number:

29

I. Objectives:

II. Explain how Switch A (A1, A2, and A4) affects the frequency response of the differential amplifier located in Section B of the panel. A1:……………………………………………………………………..

A2:……………………………………………………………………..

A4:……………………………………………………………………..

III. If Tp1= 2Vp-p, Calculate the maximum diff voltage and the cut-off voltage at Tp6.1. ……………………………………………………………………..

……………………………………………………………………..

IV. What is the main function of the notch filter located in section (E) in the panel? ……………………………………………………………………..

……………………………………………………………………..

30

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.

31

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.

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 the Table below.

# Noise sources How to minimize it?

1 60 or 50 Hz power line interference

Notch filter (section E)

2 Circuit Noise (IC's) Good Design and Good Components, BIFET amplifiers generally have low noise levels.

3 Other biopotentials, when measuring ECG, everything else creates noise like other biopotentials (EEG, EMG or EOG)

Band-pass Filters, these biopotentials have characteristics frequencies (frequency response) as shown in Table #2

4 Motion artifacts (man-made noise)

Relaxed subject

5 Electrode Noise High quality electrode and good contact

32

Table#2

We can control and change the frequency range in the panel (according to the bio signal we measure) using the control switches: A1, A2 and A4.

************************************************************

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 385-1 Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. jumper leads.

Signal Frequency Range (Hz)

Amplitude (mV)

ECG 0.3-50 QRS complex= 1mV

EMG 3-2000 Relaxed Muscle: .01-0.1 Contracted Muscle: 0 .3-0.5

EEG 0.3-30 0.002- 0.05

33

GainNoiseOutputNoiseInput

Experimental Procedures:

** Switch A3 is closed in all steps of this experiment. ** I. Measuring the output noise voltage (Nout): Input: Use jumper leads to ground test points Tp2 and Tp3 so that there is no input signal. Output: From Tp6.1 in all steps using the digital scope. a. Measure and record the Nout (p-p)with: 1. Both A1 and A2 open………………………

2. A1 closed and A2 open………………………

3. A1 open and A2 closed………………………

4. Both A1 and A2 closed………………………..

II. Calculating the Input noise voltage (Nin): Steps: 1. Measuring the total gain of the differential amplifier Adiff. Input: Using the function generator feed a 1Vp-p ,10Hz and sin wave into Tp1. Adiff = ……………………………………. 2. Compute the Nin levels for each of the Nout levels determined in step a using the following equation

1. Both A1 and A2 open……………………… 2. A1 closed and A2 open………………………

34

3. A1 open and A2 closed……………………… 4. Both A1 and A2 closed………………………. III. Measuring the signal to noise ratio (S / N) Input: Using the function generator feed a 1mVp-p differential signal at Tp2 and Tp3, 10Hz and sin wave into Tp1. With Both A1 and A2 closed, Measure: 1. The signal voltage (S):…………………………….

2. The Nout 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 1mVp-p differential signal at Tp2 and Tp3, and sin wave into Tp1. Output: From Tp15 using the digital scope. *Close A1, A3, B1 and B3. *Open A2, A4, B2 and B4. 1. Measure and record the upper cutoff frequency (upper 3db response): a. Maximum Vout = ……………………………… b. Cutoff voltage (Vcutoff ) = ……………………………… c. FH = ……………………………………………

35



BME 418

Exp.4 Noise in Biomedical Amplifier System

Pre-lab

Name:

Number:

36

I. Objectives:

II. Explain the main noise sources in the panel and how to minimize it? …………………………………………………………………………...

…………………………………………………………………………...

…………………………………………………………………………...

…………………………………………………………………………...

III. The noise output No at Tp6.1 =30mV, calculate the noise the input noise (Nin)

…………………………………………………………………………...

…………………………………………………………………………...

…………………………………………………………………………...

37

EXP#5: The Electrocardiograph Recording (ECG)

.

Theory: 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.

38

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 Left Arm LL Left Leg RA Right Arm RL 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 0.1 - 10 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 0.1 - 100 Hz, 5. A high common mode rejection ratio (CMRR).

39

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 signal in comparison to the differential ECG signal. A high CMMR would mean that the AD is much larger than AC, 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 bio-potential 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.

40

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:

I. ECG simulated test:

Follow the ECG system shown in Figure#3 on the SIP 358-1. 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. If the gain of the differential amplifier (section B) = 358,calculate the amplitude of the R and T waves generated by the ECG simulator.

5. Measure the gain of the output amplifier

41

6. Fill Table #3:

Portion Amplitude (V) Width (sec)

P P-Q -------- QRS

S ST --------- T

Two adjacent R waves

---------

Table#3

II. Recording human ECG:

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< 50KΩ,why? 4. Select lead II, plots your output, and fills the Table #3

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!

Questions 1. What does a double beat mean? …………………………………………………………………………………

42

2.. 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.

Hint: Return to step# I.4

43



BME 418

Exp.5 The Electrocardiograph Recording

Pre-lab

Name:

Number:

44

I. Objectives:

II. Complete the following block diagram (ECG system)

III. If the number of beats per minute = 70BPM, calculate the period between two adjacent R-waves in seconds. …………………………………………………………. …………………………………………………………. IV. What are the most important properties of the ECG amplifier? ………………………………………………………… ………………………………………………………… …………………………………………………………

45

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 signal1.

1 Figure#1 shows the wave shaping for one beat only.

46

1. Pulse Amplifier (section D): Amplify the signal. 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. Section (I) consists of two circuits: Balanced Splitter (transistor Q2) and Full-wave rectifier (D7- D10). 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 negative2 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 its duration (pulse width). The rectangular pulse must have constant amplitude and pulse width, it is obtained from a Schmitt trigger NAND gate connected as monostable oscillator. This circuit produces fixed amplitude and pulse width pulses. This pulse could be obtained from a comparator, Schmitt trigger, or Overdriven amplifier. Each of these circuits produces fixed amplitude pulses. Although the amplitude is fixed, pulse width may change, so you must connect a circuit that produces fixed duration pulses, for example a 555 timer connected as monostable. See Figure # 2.

2 Negative R wave means lead reversal on a patient.

47

Pulse width at Vo2 = CR1.1 The IC 74LS132 (section k) is a quad Schmitt trigger, as shown in Figure# 2. One of them used as a pulse stretcher (section J) which produces a positive pulse for each R wave, R53 and C31 set the on period (pulse width) of the pulse.

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.

48

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. Shorter pulse duration cause a chirpy sound, 0.1 second is a reasonable time when both visual and audio indicators are involved. Each time the Schmitt trigger is pulsed, the light flashes. The other two Schmitt Trigger NAND gates of the IC74LS132 shown in Figure#3 are used as a pulse tone generator as shown in Figure#4 below.

The first NAND gate act as an oscillator that produces pulses within the normal human audio range (20_20K) Hz. The frequency of the audio pulses (Tp19) generated by the oscillator is controlled by R57 and C33 using the following equation:

3357

65.0CR

f

The second nand gate inserts the audio pulses at Tp19 with the pulses at Pin 3. The wave shape at Tp20 is shown in Figure# 1.

49

The IC74LS132, 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. Audio pulses can be formed by using a 555 timer connected as a stable as shown in Figure #5 below,

And the frequency of the output pulses =CRR )2(

44.1

21

******************************************************** 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 385-1 Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. Jumper leads

50

Experimental Procedures: Input: Using the function generator feed a 0.5Vp-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?

51

3. Calculations: 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):……………………………… *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?

52



BME 418

Exp.6

I. Analog to Pulse shaping

II. Visual and Sound Pulse indicators

Pre-lab

Name:

Number:

53

I. Objectives:

II. Explain the main function of the following: Pulse Amplifier:………………………………………………………..

Polarity Correction Circuit:…………………………………………….

Pulse Stretcher:…………………………………………………………

Pulse Tone Generator:…………………………………………………

III. The IC 74LS132 located in (Section K) is a quad Schmitt-trigger, What is the main function of each one (a, b, c, and d)? a: ………………………………

b:………………………………

c:………………………………

d:……………………………..

54

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 previous 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 Tp22 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 capacitor in the feed-back) 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 details in exp#8.

************************************************************ Objectives

1. Study how the rate of a periodic signal can be counted 2. Study the double integrator circuit.

55

Material Required: 1. SIP 385-1 Kit 2. Digital storage Oscilloscope 3. Function Generator 4. DMM. 5. jumper leads

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?..........................

56

4. Observe and record the wave shape at Tp22 and measure the DC voltage output. 5. Draw on the same graph the wave shape of the signals at the input of integrator/metering circuit and at Tp22. 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)? ...........................

57



BME 418

Exp.7 Rate Meters

Pre-lab

Name:

Number:

58

I. Objectives:

II. Define the pulse averaging method. …………………………………………………….. …………………………………………………….. III. Draw the wave-shape at TP22.

59

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

Tf 60

Where: 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 OP in the panel using the function generator is shown below: Tp1 amplifiers D1, D2 and D3 (Section M)) Comparator D4 P.L.L (Section O) Frequency counter (Section P).

60

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.

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

61

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. 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.

************************************************************

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.

62

Material Required: 1. SIP 385-2 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 385-2 kit

2. Using function generator, feed 1Hz, 1vp-p and sin wave into Tp1 3. Set the two Rate/Temp switches to rate position. In addition, 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 TP11. ……………………………………………………………………….

8. 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 TP10.

10. The second section of ICM14566B provides a division by………..

11. The phase comparator located in U1 14046 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?

63

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 fingertip or ear lobe) and photo-detectors (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 increases, 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 R5) and the processing circuit described in Part. I of the experiment (sections M-O-P). The amplifier, with its law-frequency band-pass, has a frequency response of 1 to 20 Hz and a gain of approximately2, 000. The optical sensor can be a photo-resistor, photodiode, 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.

64

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.

65

:bjectivesO

1. Explain how the peripheral pulse is recorded from a finger. 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 385-2 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

66

oscilloscope to the output jack (Section M) and record the wave shape. 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?

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 20-30 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.

67

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. 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 TP3……………………………………..

13. Find the voltage level on TP 1. Determine the gain of the circuit …………………………………………………………………. 14. Measure the upper cut-off frequency? ………………………………………………………………………………… 15. Which resistors establish the voltage reference of the comparator? …………………………………………………………………………………

68



BME 418

Exp.8

I. Pulse Rate Digital Meter

II. Pulse Rate by Photoplethysmography

Pre-lab Name:

Number:

69

I. Objectives:

II. For the pulse rate digital meter block diagram shown in the manual, what is the main purpose of the comparator and P.L.L? ……………………………………………. ……………………………………………. ……………………………………………. III. For the P.L.L block diagram shown in the manual, if the frequency of the signal at Tp4= 1 Hz, calculate the frequencies at:

Tp8=……………….

Tp9=………………

Tp10=………………

Tp11=………………

IV. Explain how the photoplethysmograph measures number of pulses per time? …………………………………………………….. …………………………………………………….. V. What are the main components of the photoplethysmograph monitor? 1.

2.

3.

70

EXP#9: 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.

oTTB

oTH RR11

Where RTH: Thermistor Resistance. Ro : Resistance at temperature To(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.

71

1TVn

DV

IsI

Where I: diode current.

IS: Reverse bias saturation current.

VD: Voltage across the diode.

VT: Thermal voltage= q

KT

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

72

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, 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 that used in temperature measurements. 3. Evaluate the performance of typical circuit used in temperature measurement.

Material Required: 1. SIP 385-2 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.

73

c) Insert the plug of the temp probe into the jack in section N.

d) Adjust R30 until the digital display reads the same as Room Temperature.

e) Place the C/F switch in the F position and adjust R89 to obtain the

equivalent Fahrenheit temperature. F = 9/5 C + 32.

f) R88 is calibrated to read 37C when the probe is not inserted, remove the

probe and adjust R88 for a 37C reading.

1. Insert the sensor into experimental panel and set the Rate/Temp switches to temp. 2. Cover the probe with a plastic sheaths, place the covered probe under your tongue. Record your oral temperature.

…………………………………………………..

3. Record the surface temperature of the skin at selected sites as in Table#1.

Site Temp( Co)

Forehead-frontal

Neck, side

Right forearm

Right forefinger

Table#1 4. Check the linearity relationship between a voltage change due to a temperature rise and the change in frequency at TP7 (VCO output), measure the voltage at TP6 and TP5 and measure the frequency at TP7.

74

Temp in °C VTP5 V TP6 Freq at TP7

Room Temp……..

Oral Temp……..

Between thumb and fore finger……….

Table#2

5. Plot the relation between:

1. The temperature and the output voltage at TP6.

2. The temperature and the frequency at TP7.

75



BME 418

Exp.9 Temperature Measurement

Pre-lab Name:

Number:

76

I. Objectives:

II. What are the main differences between diode probe and thermistor probe?

1. ………………………………………………………………..

2. ………………………………………………………………..

III. What is the main function of LM566 used in the block diagram of the temperature

digital meter?

………………………………………………………………..

………………………………………………………………..

IV. Calculate the frequency of the signal at Tp7 if the voltage at pin 5 of LM566 = 3volts

and the C/F toggle switch in the C position (return to LM566 datasheet).

………………………………………………………………..

………………………………………………………………..

77

EXP#10: 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)

78

A temperature sensitive diode is held under one nostril. The short time constant3 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 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 385-2 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.

3 Time constant of a medical sensor is the time required for the sensor to reach 63.2 % of its final response.

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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 SIP385-1. 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.

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)?

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BME 418

Exp.10 Respiratory Rate

Pre-lab

Name:

Number:

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I. Objectives:

II. Explain how the temperature sensor (diode probe) measures the number of breaths

per minute?

…………………………………………………….

…………………………………………………….

III. Explain the operating principle of the respiratory rate block diagram shown in the

manual.

…………………………………………………….

…………………………………………………….

…………………………………………………….

…………………………………………………….

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Exp#11: 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 psycho-galvanic 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 (0.3-25 Hz) is needed to remove extraneous bio-potentials and other artifacts. As with the ECG measurements, the test results are adversely affected by a high electrode contact resistance.

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Galvanic Skin Potential (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) 566Tp17Audio amplifierLoud Speaker 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 C22 and R71 to R80. A DC voltage change on pin 6 of the IC will also shift the frequency of oscillation.

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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) =

RCV

VV C2

Where VC: 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 385-2 Kit 2. Digital storage Oscilloscope 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?

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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.

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

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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 KΩ),Ic. 14. From Ic, calculate the voltage drop across R50 (470 Ω) 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) =………………………………..

18. Can you replace the 566 with a 555timer (a stable)? And why?

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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 bio-potential surface recordings of this type.

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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 Material Required:

1. SIP 385-1 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

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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 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.

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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. User-programmable instruments require that montages be programmed at the user’s 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,

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Parietal, and occipital as shown in Figure#3.

Table #1: EEG Signals, Frequency and voltage levels ************************************************************ Objectives:

1. Describe how EEG is recorded. 2. Record EEG pattern on a subject 3. Evaluate the performance of EEG amplifiers.

Material Required:

Type Frequency in Hz

Amplitude in µV Conditions

Alpha 8-14 30-50 Awake, resting

Theta 4-8 20-40 Stress, Frustration

Beta 14-50 5 Stress, Tension

Delta 1-4 Varies Sleep, Brain disease

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1. SIP 385-1 Kit 2. ECG lead selector 3. EEG paste 4. EEG electrode cable 5. Alcohol 6. Digital storage Oscilloscope 7. DMM Experimental Procedure: 1. Consider the EEG recording system which consists of section A, B, C, F and

G. 2. The first site to be observed is located on the temporal region of the head. 3. Connect the EEG electrodes cable into the lead selector box, select lead I on

the lead selector. 4. Insert the plug of the lead selector into the jack of SIP385-1.

5. Place the subject, with eyes closed, on a blanket-covered table (in a dimly-

lighted room, if possible). Attach the electrode to the recording sites using electrode paste to hold the electrodes in place. Tape can be used to help hold the electrode in place until the paste dries.

6. On the panel, select a 0.3 Hz to 50 Hz frequency response by closing switches

A1, A3, and A4 (switch A2 remains open). Open switches Bland B4 and close switches B2 and B3. This connection inserts the notch filter. Position the "DIFF/COMM" switch to the OFF position.

7. Connect the oscilloscope to the output of the amplifier (section G). Then

slowly rotate the Sensitivity control on the panel and observe the tracing on the oscilloscope. Adjust the vertical sensitivity of the oscilloscope for a 1-2 cm display.

8. Have the test subject quickly open and close his/her eyes. From the

oscilloscope display, determine if eye-blinking spikes are observed. If eye-blinking spikes are not observed, increase the sensitivity further.

9. With the eyelids closed, have the test subject shift his or her eyes rapidly from

center to right and center to left. Can you observe pattern changes associated with the eye movement? Make a number of observations until you know what you are observing. Observe the difference between right and left, and up and down.

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10. Does movement of the eyes to the right produce a positive or negative going pulse? What does movement to the left produce? What does movement of the eyes up and down produce?

11. The next site to be observed is located above the eyebrows, near the edge of the hair line (Frontal region). Leads I and II will be placed high above each eye, and the common lead is placed below the earlobe, on the neck.

12. Record an EEG tracing. Have the test subject open and close his or her eyes and determine if eye-blinking spikes are observed. If not, readjust the Sensitivity control on the panel until spikes are observed.

13. Position one EEG electrode on the right Frontal region and one on the right Parietal region. Use the oscilloscope to make a recording of the waves present.

14. The alpha rhythm will be observed next. The frequency of the alpha waves is in the range of 8-14 Hz. To select this bandpass, switch in the bandpass amplifier by opening switches B2 and B3, and closing B1 and B4. The bandpass filter also provides additional gain.

15. Allow the subject to relax in complete silence until he or she starts to doze. On

the oscilloscope or Compucorder observe the pattern, amplitude and types of waves present. Count the number of waves produced per period and determine the frequency of the waves present.

16. While the subject is lying on the table, with eyes closed and presumably relaxed, present him or her with a problem difficult enough to cause frustration to the test subject; i.e., the multiplication of two number by a third. Are the observed wave patterns affected? Theta waves (4-8 Hz) increase in amplitude with frustration. Do you observe any pulses in this frequency range?

17. Bypass the alpha filter (8-14 Hz) by closing and opening the appropriate switches, since it also filters out the theta waves. Subject the person to various forms of harsh stimulation. Use loud noise, physical touch, odors, bright lights, and other activities which might cause a fright, tension, and stress in the test subject. Observe the effects on the wave patterns that 13

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EEG Amplifier characteristics

*Close A1, A3, B2 and B3.Open A2, A4, B1and B4. *Input: The differential signal at (Tp2-Tp3) = 100microvolts and 10 Hz. Measure: 1. AC Gain provided by the Opto-coupler (C): …………………………………………………… 2. AC Gain provided by the Notch filter (E): …………………………………………………… 3. AC Gain provided by the output amplifier (G): …………………………………………………… 4. Close B2 and B4, and open B1 and B3, What is the gain of alpha filter? …………………………………………………… 5. What is the total gain of the entire system? a. with no 8-14 Hz filter? …………………………………………………… b. with 8-14 Hz filter?

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References: 1. SIP385BM

Biomedical Instrumentation

Author: Morris Tischler.

2. Electronic Design

Circuits and systems

Second edition

Author: C.J. Savant,Jr, Martin S. Roden, and Gordon L. Carpenter.

3. URL: http://www.bme.utexas.eduiugrad/UGLab/

4. URL: http://www.omgsic.com

Biomedical Instrumentation Lab 1

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