Using Biopotential Amplifiers in High School Science

Using Biopotential Amplifiers in High School Science

Dennis McGuire

Central Valley High School

Spokane Valley, WA

&

Jennie Buetow

Pre-service teacher

Washington State University

Pullman, WA

Washington State University Mentor:

Dr. David Lin

Bioengineering

July 2006

The project herein was supported by the National Science Foundation Grant No. EEC-0338868: Dr. Richard I. Zollars, Principle Investigator and Dr. Donald C. Orlich, co-PI.

The module was developed by the authors and does not necessarily represent an official endorsement by the National Science Foundation.

Introduction:

Overview of Project:

A Biopotential Amplifier (BPA) is a device used to read electrical impulses created in living tissues. These electrical impulses include electromyograph (EMG; muscle contractions), electrocardiograph (EKG; heart contractions), and action potentials in nerves. The use of a Biopotential Amplifier in a high school classroom can aid students in understanding the way in which these electrical impulses travel through muscles and nerves. This module will aid teachers in explaining the phenomenon of how the human body is an ‘electrical generator’ to their students through generalized instruction as well as hands-on laboratories.

The lessons included in this module primarily focus towards a tenth grade Biology course and an eleventh or twelfth grade Anatomy course. The activities can be adjusted to fit the needs of both of these classes by varying the intensity of the laboratory experiments as well as the depth to which the teacher chooses to instruct the students. For both the Biology and Anatomy courses, the module is geared towards analyzing how electrical signals are passed to the muscles via nerves by looking at the EMG or EKG graphs generated on the oscilloscope/computer screen. Another way to utilize this module would be in an advanced Physics course where the focus would be on the construction of the Biopotential Amplifier (however, it is not specified in this module). One primary goal of this module is to construct it in a way that it can be easily manipulated to fit the needs of the class in which it is being used.

Intended Audience:

The intended audiences for this module include students in a 10th grade Biology course and also students in an 11th/12th grade Anatomy course.

Estimated Duration:

In a Biology course, this module is intended to last approximately five 50 minute periods. In an Anatomy course, the estimated duration is eight to ten 50 minute periods. Another option for the Anatomy course is to use the Biopotential Amplifiers throughout the year as a tool to see which muscles are activated during different motions. All of the periods, in both classes, will include various combinations of teacher instruction and teacher demonstrations as well as student centered laboratories and discussions.

Rationale:

It is important for students in a Biology course and Anatomy course to fully understand the basis behind the ways in which the human body operates. This module will help students make their own discoveries in how muscles work to allow movement in the body. By using the laboratories in this module, the students will get to see electrical impulses occurring in their own bodies, and can then relate this information to how the human body acts as an ‘electrical generator.’ The hope is that because the students will be able to use the Biopotential Amplifiers themselves and read the data from their own muscles, it will make the learning more relevant and meaningful. When knowledge is meaningful, it allows for better understanding and longer retention of the information.

When BPA’s were first used, it was simply an interesting development (see “History” section). The practical application and use of BPA’s were the outcome of engineering processes. Using these activities in the classroom will aid to introduce engineering, more specifically bioengineering, to high school students. It may spark some interest for science students to further pursue engineering as an occupation.

Lastly, this module addresses many of Washington State’s Essential Academic Learning Requirements, EALR’s and the Grade Level Expectations, GLE’s, (see section titled “Goals” for further detail).

Science:

A biopotential amplifier reads the activity of muscles during a phase of contraction. BPA’s have been around for many years and are used in medicine all the time for reading the output of the heart muscle (EKG, electrocardiograph), or for reading muscle activity in other parts of the body (EMG, electromyograph). They are extensively used in medical applications, but are rarely used in the classroom. The science behind this device is quite complex.

Each cell membrane (for every cell in the human body) acts like a capacitor. In other words, there are more charged particles on one side of the membrane than the other. The membrane represents a barrier which prevents various fluids in the intracellular and extracellular (interstitial) fluids from mixing. Most cells in the organs of the body tend to keep a fairly constant potential across their cell membranes. (A more common term for potential is voltage). In normal cells, this voltage is kept constant (approximately –60 to –90 mV with the – sign meaning that the interior of the cell is negative). Nerve cells and muscle cells are different from other cells in the body in that they have the ability to have the charges move along the membrane, creating an electrical current. This is called the action potential. When an action potential moves along a nerve cell, potassium and sodium ions are selectively “pumped” through the cell membrane by transport molecules and mechanisms present both in the interstitial fluid and intracellular fluid, thus changing the ion concentration levels on either side of the cell membrane. This rapid transport of charged molecules through a membrane creates an electrical current which flows along the membrane of the nerve cell. The next nerve cell will receive a message that a signal is being sent and it repeats the process. This allows the signal to transmit itself along this corridor of cells very rapidly. A signal can travel from your brain to nearly every muscle in your body fairly instantly. When a muscle receives a signal to contract, the action potential continues along the muscle cells.

Muscle cells have the ability to contract and produce force. Muscle contraction and force production are due to a change in the relative positions of various filaments arranged in the interior of the muscle. The filaments are composed of the proteins actin and myosin. Each muscle fiber is arranged in short subunits called sarcomeres. During a contraction, the actin and myosin filaments cross over one another creating a shortened fiber of actinomyosin. Therefore, each sarcomere is shorter, resulting in a shorter muscle fiber. These shorter fibers are the cause of the contraction of that muscle. The initiation of that muscle contraction is caused by the action potential that was sent from the nerve and initiated in some way by your brain.

Electromyography, the recording of the pattern of muscle action potentials, represents an adequate parameter for the analysis of muscle activity. An EMG is a readout of the voltage differences between two points on a muscle created during the period of time of the muscle contraction. The time course of a muscle contraction, the contraction force, and the coordination of the activities of several muscles can be measured from the amplitude and the frequency spectrum as well as from the changes in these values over time. The biopotential amplifier (BPA) is one such device that can read these values and can be shown on an oscilloscope or computer, or can even be heard physically in headphones because the common frequencies of muscle contractions are within the range of human hearing.

The physics of electrical currents is very important also. When a current flows along a resistive element, it produces a potential difference between any two points along that element. When a current changes either the direction or the size of the flow, the potential difference changes also. The same thing is happening with a nerve signal. During the action potential, a current is flowing, causing a corresponding potential difference. These potential differences change exactly as the current changes. Therefore, a device can be built to read these changing potential differences and to reproduce the same signal that is causing the potential difference change. The macroscopic analog is a simple voltmeter that is used to read a voltage drop across a resistor in a circuit. Ohm’s law states that the voltage drop is equal to the current times the resistance, (V=IR). In the human example, a current is being produced by differences in the number of charges present on either side of the cell membrane. Since those charges are present both intracellular and extracellular, a current is flowing both along and within the nerve and muscle cells. The electrodes being placed on the skin (the resistor) are the two ends of a voltmeter and the EMG is the readout of the voltage differences produced by the current flow. Since the initial potential differences are so small, the BPA must have amplifiers to get the signal to a useable range.

Historical Perspective:

Electrodiagnostic methods began as early as Helmholtz in 1850 when he measured the conduction velocity of a nerve impulse along peripheral nerves. However, there were no clinical applications until the 1940’s in animal experimentation showing that conduction velocities are slowed after accidents and injuries that caused some nerve damage. The first recorded electromyogram was in 1912 by Piper who recorded potentials during voluntary muscle contractions using surface electrodes and a galvanometer. This technique was not diagnostic, but aided in providing anatomical information. In 1929 the concentric needle electrode developed by Adrian and Bronk allowed for the study of action potentials along single muscle fibers. All of these methods were developed more fully with the invention and use of the cathode ray tube and were further enhanced with the new technologies developed during World War II.

These methods are used clinically in many different applications. Denervation after an injury, disorders of nerves cells and axons, neuromuscular blocks (caused by diseases or injuries), muscle diseases, spastic conditions, and abnormal functioning of the motor functioning of the brain itself are just a few ways that BPA’s can and are used.

Bioengineering:

Engineers are problem solvers. They either take existing scientific principles and apply them, or they do what is necessary to solve the problem and then the science may come later. This practical application of science to problem solving is what engineering is all about—creating new technologies to help society.

Bioengineers are involved at the cusp of where biology meets engineering. The major emphases in this area are technologies affecting human and animal health and well-being. Bioengineers apply engineering methods and concepts to living systems. They also utilize biological methods and concepts to improve engineering practice. There are many problems in the health care and medical industry that need an engineer working with a healthcare professional in order to find the best solution. Bioengineers might develop materials to speed tissue repair in burn victims or design new equipment to aid doctors in surgical procedures. They might work with hibernating bears to discover why muscles do not degrade during the time of non-use like bedridden human muscles do. Or, they might study the gait and stride pattern of cerebral palsy patients in order to help them in their daily quality of life. The diversity of possibilities for bioengineers is seemingly endless.

The biopotential amplifier was created by bioengineers to study how muscles function both in normal use and during times of disease where either muscles or nerves do not work in any normal manner. With this device, bioengineers can study how and when muscles are being activated. In disease or injury situations, muscles may not be being activated in a sequential fashion in order to perform a common daily activity such as walking. The BPA will show the muscle firing sequence and steps can be taken medically to help correct the problem. In one case taken from the Shriners Childrens Hospital, the Rectus femoris muscle was not firing in a sequential manner and was inhibiting normal walking by the patient. Doctors decided to move the attachment point to the back of the knee so that the muscle now flexes the knee instead of extends it at the wrong time. This allowed the patient to walk in a more normal fashion, enhancing their quality of life. With bioengineering and medical procedures, many quality of life issues are being solved.

Goals/Learning Objectives (GLE’s):

Learning Objectives

· Students will be able to:

1. Define the following terms-

electrolytes

interstitial

voltage

kinematic

intracellular

potential difference

sarcomere

actin

myosin

actinomyosin

potential

capacitor

agonist

antagonist

· Students will know:

1. how the cell membrane acts as a capacitor (cognitive; comprehend)

2. what electrolytes are and why they are important (cognitive; application)

3. basic nerve functions including: (cognitive; comprehend)

· Electrolyte balance & imbalance creating a potential difference

· Action potentials

4. how a muscle contracts: (cognitive; comprehend, apply)

· Action potentials

· Sarcomeres

· Actin/Myosin: Actinomyosin

5. how to compare and contrast heart muscle contraction with skeletal muscle contraction. (cognitive; analyze)

6. nerve and muscle functions to describe how the human body acts as an “electronic device” (cognitive; synthesis)

This module will address the following skills pertaining to the WASL test:

GLE 2.1.1 Understand how to generate and evaluate questions that can be

answered through scientific investigations.

(9, 10) Generate a new question that can be investigated with the same materials and/or data as a given investigation

GLE 2.1.2 Understand how to plan and conduct systematic and complex scientific investigations.

(9, 10) Make a hypothesis about the results of an investigation that includes a prediction with a cause-effect reason.

(9, 10) Generate a logical plan for, and conduct, a systematic and complex scientific controlled investigation with the following attributes:

Hypothesis (prediction with cause-effect reason)

Appropriate materials, tools, and available computer technology

Controlled variables

One manipulated variable

Responding (dependent) variable

Gather, record, and organize data using appropriate units, charts, and/or graphs

Multiple trials

Experimental control condition when appropriate

Additional validity measures

(9, 10) Generate a logical plan for a simple field investigation with the following attributes:

Identify multiple variables

Select observable or measurable variables related to the investigative question

(9, 10) Identify and explain safety requirements that would be needed in an investigation

GLE 2.2.5 Understand how scientific knowledge evolves.

(9) Explain how existing ideas were synthesized from a long, rich

history of scientific explanations and how technological advancements changed scientific theories.

(9, 10) Explain how scientific inquiry results in new facts, evidence,

unexpected findings, ideas, explanations, and revisions to current theories.

(9, 10) Explain how results of scientific inquiry may change our

understanding of the systems of the natural and constructed world.

(9, 10) Explain how increased understanding of systems leads to new questions to be investigated.

(9, 10) Explain how new ideas need repeated inquiries before

acceptance.

(9, 10) Use new tools to investigate a system to discover new facts about the system that lead to new ideas and questions.

Equipment:

· Biopotential Amplifier (BPA) Module

· Computers or Oscilliscope

· Free Oscilliscope computer program

· Wiring (to connect BPA to computer soundcard)

· Speakers or headphones

· Biopotential Amplifiers

· Supplies for constructing BPA*:

· PC Board

· Instrumentation Amp

· Operational Amps

· Resistors

· Capacitors

· Connectors

· Wire

· Battery Pack

· Electrodes

· Balance Board

*See appendix for wiring diagram, instructions for building BPA, and a list of suggested parts suppliers.

Prerequisite Student Skills/Knowledge:

· Tenth grade Biology students: assume no prior knowledge.

· Eleventh/Twelfth grade Anatomy students: basic cell structure and functions.

Procedures:

Safety Precautions:

LAB SAFETY PROTOCOLS

· Perform laboratory work only when your teacher is present.

· Always read and think about each laboratory assignment before starting.

· Know the location and use of all safety equipment in your laboratory. These should include the safety shower, eye wash, first-aid kit, fire extinguisher, and blanket.

· Wear a laboratory coat or apron and protective glasses or goggles for all laboratory work. Wear shoes (rather than sandals) and tie back loose hair.

· Clear your bench top of all unnecessary materials such as books and clothing before starting your work.

· Check chemical labels twice to make sure you have the correct substance. Pay attention to the hazard classifications shown on the label.

· Some chemical formulas and names differ by only a letter or number. Pay attention to the bottle or jar and to your own test tube or beaker. DO NOT return any excess material to its original container unless authorized by your teacher.

· Never taste laboratory materials. No food, drink, or gum in the laboratory.

· Never look directly down into a test tube; view the contents from the side. Never point the open end of a test tube toward yourself or your neighbor.

· Any laboratory accident, however small, should be reported immediately to your teacher.

· In case of a chemical spill on your skin or clothing rinse the affected area with plenty of water. If the eyes are affected water-washing must begin immediately and continue for 10 to 15 minutes or until professional assistance is obtained.

· Minor skin burns should be placed under cold, running water.

· When discarding used chemicals, carefully follow the instructions provided.

· Return equipment, chemicals, aprons, and protective glasses to their designated locations.

· Before leaving the laboratory, ensure that gas lines and water faucets are shut off.

· If in doubt, ask!

(Adapted from www.chemvt.edu/rvgs/act/lab/safety_rules.html, 6/29/06)

Teacher Materials and Worksheets:

This BPA will be used in an Anatomy class throughout the year as a learning tool during normal classroom activities concerning muscle activation. This usage of the device will not require a full understanding of either nerve activation potentials or precisely how muscles work. There will be labs and other activities which will focus on those specific topics later on in the school year.

Example:

While the students are learning about the ankle joint, the type of joint it is and all the bones and muscles involved, and all the motions that the joint can perform, the BPA can be used to show which muscles are causing dorsiflexion and plantarflexion.

1. Attach the BPA to the Tibialis anterior and to the computer oscilloscope.

2. Stand on your toes.

a. Describe what you see happening on the computer screen.

b. Why are you seeing what you are seeing?

3. Lift your toes off the floor while your heel is still on the ground.

a. Again describe what you see on the computer screen.

b. Why do you see something different from standing on your toes?

4. What conclusion can you make about the action of the Tibialis anterior muscle?

This sort of activity can be done at any time to give a visual example of the functioning of muscles. This does not require the background that later labs will require. It also allows the students to be actively involved in the normally dull memorization of muscle actions.

Teacher Demonstration (Lab #1):

Instructional Strategies:

Electrocardiograph using BPA

· Attach Biopotential Amplifier (BPA) to left & right wrists via electrodes of either student volunteer or teacher.

· Attach leads to computer sound card

· Run through Freeware oscilloscope

· Observe EKG readings on computer screen/projector

· Discuss as a class what is seen on the screen.

· Form of the waves (Review PQRS waves of a heart beat and what each represents)

· Hand out sample EKG printout strip to students, or have students generate own graph of the EKG seen on the screen.

· Questions to ask students:

· Describe in detail what you see

· Provide a plausible explanation for what you are observing

· What does the separation of the peaks represent?

Data Collection:

· Read graph on screen of EKG recording. Write down voltage numbers of all ‘peaks’ and ‘valleys’ on the graph. Students generate graph on paper for analysis.

Data Analysis:

· Analyze graph of EKG, describe each voltage change and what it represents.

Conclusions:

Ask students questions:

· Describe in detail what you see on the graph.

· Provide a plausible explanation for what you are observing.

· What does the separation of the peaks represent?

Evaluation Protocols:

· Formal Assessment: collect answers to the questions which the students have answered.

· Informal Assessment: student participation in discussion, and students on task with handout.

Supplemental Teacher Information:

EKG components and intervals

Illustration copyright 2002 by Nucleus Communications, Inc. All rights reserved. http://www.nucleusinc.com

An electrocardiogram (EKG, ECG) translates the heart's electrical activity into line tracings on paper. The spikes and dips in the line tracings are called waves.

The P wave represents the electrical activity in the atria. The Q, R, and S waves—called the QRS complex—represent the electrical activity in the ventricles. The T wave represents the electrical recovery, or repolarization, of the ventricles.

Name:

1. Describe in detail what you see on the graph.

2. What do you think it means to have voltage on the Y-axis?

3. Besides just time, what does the separation of the peaks on the X-axis represent?

4. Provide a plausible explanation for what you are observing.

Electromyography—Lab # 2

PROCEDURE

1. Attach BPA via electrodes to Bicep brachii muscle

a. With arm relaxed and lying on the table:

i. Describe what you see on the screen

2. Have a partner gently hold your arm on the table.

a. Attempt to flex your arm up:

i. Describe what you see on the screen

3. Attach the BPA to headphones as shown by your teacher.

a. Perform the same exercises as before.

i. Describe what you hear in the headphones.

ii. Why can you hear anything at all?

4. Reattach the BPA to the sound card on the computer.

a. Flex and relax your bicep repeatedly and rapidly

i. What do you see happening?

ii. How does this differ from what you saw in part 2?

5. Additional exercises—

a. With your bicep can you recreate the image that you saw on the ECG when your heart was beating?

i. Explain why you think this cannot be done.

ii. Can you reach any conclusions about your heart muscle in comparison to your bicep?

CONCLUSION—Write a conclusion on the back of this sheet describing what you learned by doing this lab.

Anterior / Posterior Muscle Activation

(Lab #3)

Procedure:

· Place BPA electrodes on lower posterior right leg on gastrocnemius/soleus complex.

· Place 2nd set of electrodes on anterior aspect of leg on the Tibialis anterior.

· Attach stereo headphones

· Standing normally, raise yourself up on your toes.

· What do you hear?

· What is happening?

· Now drop back down and raise your toes up, standing on your heels.

· What do you hear?

· What is happening?

· Can you tell by listening to the headphones which muscle is being activated?

· Repeat procedure on a balance board.

· What do you hear?

· Is there any difference from first exercise?

· Conclusion: Describe what you learned by doing this lab.

Balancing Lab: Proprioception (unconscious muscle contractions)

Lab #4

Name:

1. Stand on right leg, holding left leg in front of you and balance.

a. What do you hear?

b. What do you think is happening?

2. Repeat this procedure with your eyes closed.

a. Is there any difference from the first balancing? If so, what is the difference?

3. Repeat procedure on a balance board.

a. What do you hear?

b. Is there any difference from first exercise? If so, what is the difference?

4. Conclusion: Describe what you learned by doing this lab.

Throwing Lab (Lab #5)

Procedure:

1. Attach BPA to triceps muscle and to speakers (headphones).

2. Throw a balled up piece of paper.

a. What do you hear?

3. Attach BPA to gastrocnemius muscle (and to headphones). Throw the paper again.

a. What happens?

4. Experiment with various muscles on your arm, leg, or abdominals. Can you find muscles that are NOT functioning when you throw the paper?

Conclusion: Explain what you learned about the complexity of a “simple” motion like throwing a ball.

Post Lesson and Lab Evaluation

Sample Test:

Test—Muscle and Nerve Function

Short Answer--

1. Explain how nerve and muscle cells are different from other cells in the human body.

2. What are actin and myosin?

3. What is an action potential?

4. What are electrolytes?

5. Why is it important for electrolytes to be ingested into the body?

6. Why can muscles only contract?

7. Why is it important that muscles work in pairs across joints?

8. What do the terms interstitial and intracellular mean?

Long answer—

1. How is a nerve signal like an electrical current in a wire?

2. Using the terms; action potential, sarcomere, actin, myosin, and nerve, explain a muscle contraction.

Essay—

1. With your knowledge of nerves, muscles, action potentials, and kinematics, analyze and describe the intricate processes necessary for a human to take a single step.

References:

1. Lenman, J. & Ritchie A.E. Clinical Electromyography. J.B. Lippincott Co. 1970.

2. Kumar, S. & Mital A. Electromyography in Ergonomics. Taylor & Francis. 1996.

3. Goodgold, Joseph. Anatomical Correlates of Clinical Electromyography. Williams & Wilkins Co. 1974.

4. Washington State’s Essential Academic Learning Requirements. K-10 Grade Level Expectations: A New Level of Specificity (Science). Office of Superintendent of Public Instruction. 2005.

5. Xu, S., Lasher, R., Bucher, B., Jantzen, C. Impulse Laboratories: Biopotential Amplifier.

6. www.chemvt.edu/rvgs/act/lab/safety_rules.html, 6/29/06

7. http://www.webmd.com/hw/health_guide_atoz/tu6256abc.asp, 7/17/06

Appendix:

· Instructions for Building a BPA

· Suggested Parts Suppliers

· Suggested Websites for Oscilloscope Computer Programs

· Connection Diagram for Instrumentation Amp.

· Connection Diagram for Operational Amp.

· Wiring Diagram

Procedure for Constructing a Biopotential Amplifier

Part 1:

· Begin with the following parts:

· 2; Operational Amplifier (Op. Amp.)

· 1; Instrumentation Amplifier (Instr. Amp.)

· Resistors:

· 2; 8 KΩ (silver, red, red, gold)

· 6; 100 KΩ (brown, black, yellow, gold)

· 2; ~58 KΩ (green, blue, orange, gold)

· 1; 550 Ω (green, blue, brown, gold)

· 2; 10 KΩ (brown, black, orange, gold)

· Capacitors:

· 4; 15 μF

· 2; 0.1 μF

· 1; 10 KΩ 15 turn Potentiometer

Part 2:

· Arrange Instr. Amp. So that pin 1 lies in E-23

· Arrange one Op Amp so that pin 1 is in E-13

· Arrange other Op Amp so that pin 1 is in E-6

Part 3:

· Power up board by leading two wires from battery holder to lines on end of the board, designate one as positive (+) (red) and one as negative (-) (black).

Part 4:

· Run a jump wire (black) from the negative line to a line on the other end of the board. (this will make powering Amps easier)

Part 5:

· Run power to all Amps with jumper wires.

· Negative jumpers (black) should go from negative line to: A-26, A-16, and A-9.

· Positive jumpers (red) should go from positive line to: J-24, J-13, and J-6.

Part 6:

· Creating V-Ref:

· Place a 10 KΩ resistor from G-9 to positive line

· Place a 10 KΩ resistor from J-9 to negative line

· Place a jumper wire (green) from G-8 to I-7

· Place a jumper wire (green) from G-6 to outermost line.

Part 7:

· Place a 15 μF capacitor from A-25 to A-27

· Place a 15 μF capacitor from C-24 to C-28

· Place a 100 KΩ resistor from B-25 to V-Ref line

· Place a 100 KΩ resistor from D-24 to V-Ref line

· Place a 550 Ω resistor from D-23 to G-23

· Place a 8 KΩ resistor from I-25 to C-20

Part 8:

· Place an 8 KΩ resistor from A-20 to A-15

· Place a 58 KΩ resistor from A-14 to A-13

· Place a 0.1 μF capacitor from B-20 to B-13

· Place a 100 KΩ resistor from C-14 to C-10

· Place a 0.1 μF capacitor from D-15 to D-10

· Place a green jumper wire from V-Ref to A-10

· Place a green jumper wire from E-10 to F-10

· Place a red jumper wire from D-13 to F-19

Part 9:

· Place a 15 μF capacitor from J-19 to J-17

· Place a 15 μF capacitor from H-17 to H-16

· Place a 58 KΩ resistor from J-15 to J-14

· Place a 100 KΩ resistor from I-17 to I-14

· Place a 100 KΩ resistor from H-15 to H-10

· Place a 100 KΩ resistor from G-16 to G-10

Part 10:

· Place a red jumper from D-8 to G-14

· Place 15 turn Potentiometer so that wiper peg (center peg) is in C-7 (make sure dial is towards column 1 on board).

· Place a red jumper from D-6 to A-5

· Place all input and output wires:

· Black: E-28

· Red: B-27

· Red: A-6

· Green: V-Ref

Power using 4 AA batteries.

Suggested Parts Suppliers:

1. The Electrode Store

www.electrodestore.com

2. Digi-Key Corporation

www.digikey.com

3. Jameco Electronics

www.jameco.com

Suggested websites for oscilloscope computer programs:

1. www.dxzone.com/catalog/software/spectrum_analyzers

2. www.dontcrack.com/freeware/

· Select ‘sound analyzer’

· Select ‘sonogram’

3. www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=3428

· Oscilloscope and spectrum analyzer for windows

· Costs $15 to $20

Connection Diagram for Instrumentation Amplifier:

Connection Diagram for Operational Amplifier:

�

�

�

�

�

�

�

�

�

�

1

RG

+VS

Output

V-Ref

RG

- IN

+ IN

- VS

+

8

7

6

5

4

3

2

1

2

3

4

8

7

6

5

Output A

Inverting input A (-)

Non-inverting input A (+)

V-

V+

Output B

Inverting input B (-)

Non-inverting input B (+)

A

B

� A capacitor is an electronic device that is used to store charges in electrical circuits.

� Defined as the rapid change of transmembrane potentials. Voltages can go from –60 mV to +50 mV in fractions of a millisecond.

� The simple term for potential difference is voltage. Voltage is the amount of energy used per unit of charge. When energy is being used there is a difference in the amount of energy available between two points on a circuit. That is the potential difference or voltage drop.

� The major quadriceps muscle on the anterior portion of the thigh. It’s function is knee extension and hip flexion.

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