Post on 07-Apr-2018
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INTRODUCTION TO
BIOMEDICAL ENGINEERING
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Why Biomedical Engineering?
Promising future developments
Improve medicine, save lives
Numerous possibilities based upon level of biology and
engineering specialty
Hybridization of skills and knowledge
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Types of problems
Interface between biological and non-biological materials
Design, modeling, and construction of biologically-analogoustechnologies
Understanding and improving upon biological limitations
Medical tools and diagnostics
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TerminologyBiomedical engineering
Bioengineering
Also, biological engineering and others . . .
Biotechnology
Often used interchangeably with biomedical engineering. When distinguishing
between the two, typically bioengineering tends to refer to engineering using
biological substances, often at a higher level of biology than biotechnology.
The use of engineering science and math to tackle problems in medicine. When
distinguished from bioengineering, focuses more on the machine/device/non-
biological type of research.
Term that is generally similar to bioengineering, but, in comparison, refers mostspecifically to direct manipulation and use of living biological substances.
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UNIT I
Physiology and Transducers
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Human Anatomy & Physiology
Cell
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Human body develops from union ofSPERM + OVUM=FIRST CELL OF HUMAN
BODY
Group of cells
Tissues
Organs
Systems
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Structure of Cell
Cell is a structural & Functional unit of human body, capable of
carrying out functions of life independently. Nucleus
Cytoplasm
Cell Membrane
Functions of Cell- Production of Bio-Energy- Storage- Multiplication
- Specific function according to location
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Membrane Potentials
1. Resting Membrane Potential2. Excitatory Post-synaptic Potential (EPSP)3. Inhibitory Post-synaptic Potential (IPSP)4. Action Potential
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Levels of Investigation
Organism Systems(e.g. Vision)
Cell Synapsis
Next weeks
Today
Molecule
Next weeks
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Click on animation website or main website (here)
Neurons have a selectively permeable membrane
During resting conditions membrane is: permeable to potassium (K+) (channels are open)
impermeable to sodium (Na+) (channels are closed)
Diffusion force pushes K+ out (concentration gradient)
This creates a positively charged extra-cellular space.
Electrostatic force pushes K+ in
Thus, there is a dynamic equilibrium with zero netmovement of ions.
The resting membrane potential is negative (- 60mv)
1. Resting Membrane Potential
http://bcs.whfreeman.com/thelifewire/content/chp44/4401s.swfhttp://www18.homepage.villanova.edu/diego.fernandezduque/Teaching/Teach_Index.htmhttp://www18.homepage.villanova.edu/diego.fernandezduque/Teaching/Teach_Index.htmhttp://bcs.whfreeman.com/thelifewire/content/chp44/4401s.swf8/4/2019 bme unit-1
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Copyright Allyn & Bacon 2004
Cell Membrane
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15
OUTSIDE
INSIDE
K+ = Potassium; Na+ = Sodium; Cl- = Chloride; Pr- = proteins
Na+
Na+
K+
K+
Force of Diffusion
Electrostatic Force
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - -
Cl-
Force of Diffusion
Cl-
Electrostatic Force
Pr-
Closedchannel
openchannel
openchannel
nochannel
3Na/2Kpump
Resting Membrane Potential
- 65 mV
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Resting membrane potential:(things you need to know)
a. Concept of Selective membrane
b. How permeable the membrane is to proteins, K+, andNa+
c. Diffusion and electrostatic forces and how they act on
K+ and Na+d. Concept of Dynamic equilibrium
e. Concept of Membrane potential
f. ATP Na/K pump and its role in maintaining the
membrane potential
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Copyright Allyn & Bacon 2004
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Copyright Allyn & Bacon 2004
Membrane Potentials
1.RestingPotential(justdescribed)
2.ExcitatoryPost-synapticpotential
threshold4.InhibitoryPost-synapticpotential
3.ActionPotential
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2. Excitatory Post-synaptic Potential (EPSP)
Post-synaptic neuron
Pre-synaptic neuron
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1. The pre-synaptic neuron releases aneurotransmitter.
2. Neurotransmitter diffuses acrossextra-cellular space - synaptic cleft.
3. Neurotransmitter binds to post-synaptic receptor.
4. Binding of neurotransmitter causes
Na+ channels in post-synapticmembrane to open.
5. Depolarization occurs (excitatory
potential)
Post-synaptic neuron
Pre-synaptic neuron
Excitatory Post-synaptic Potential (EPSP)
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21
OUTSIDE
INSIDE
K+ = Potassium; Na+ = Sodium; Cl- = Chloride; Pr- = proteins
Na+
Na+
K+
K+
Force of Diffusion
Electrostatic Force
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - -
Cl-
Force of Diffusion
Cl-
Electrostatic Force
Pr-
Closedchannel
openchannel
openchannel
nochannel
OPEN Na+CHANNEL
+ + +
- 65 mV- 50 mV
1. Resting Membrane PotentialExcitatory Post-Synaptic Potential (EPSP)
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EPSP
EPSP is a graded potential
Multiple EPSPs are integrated acrossspace and time.
ExcitatoryPost-synapticpotential
Integration
Once the threshold isreached, voltage-dependent sodiumchannels are opened
The cell is depolarized(action potential)
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3. Inbibitory Post-synaptic Potential (IPSP)
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Human Anatomy & Physiology
Nervous System
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Nervous system
Central processing unit of body. Controls andbalance of body functions.
Divisions Central nervous system (CNS)
Peripheral nervous system (PNS)
Autonomic nervous system (ANS)
Components
Nerve cell
Sensory nerve
Brain
Motor nerve
End organ
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Functions of Nervous system
Control over voluntary and involuntaryfunctions / actions.
To control body movements, respiration,circulation, digestion, hormone secretion,
body temperature To receive stimuli from sense organs,
perceive them and respond accordingly
Higher mental functions like memory,receptivity, perception & thinking.
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Parts of CNS
Cerebrum
Cerebellum
Mid brain
Pones
Medulla oblongata
Spinal cord
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Brain Protected by skull
Three coverings of brain called meninges
Dura Arachnoid
Pia matter
Cerebro spinal fluid (CSF) between the Pia
meter and Arachnoid CSF acts as a shock absorber and provides
nutrition to the brain
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Cerebrum
Biggest part of brain, divided into two hemispheres
Contra lateral control
Outer surface is grey due to cells
Internally white due to fibers
Surface is folded to increase the area
Functions of cerebrum Intellect, memory, will power, imagination, emotion &
other psychological functions
Receive and perceive the stimuli
To give command for reaction with the help of pastexperience
To control over other parts of nervous system
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Cerebellum
Situated below and behind the cerebrum
Functions of cerebellum Controls tone muscles
Helps coordination of body movements
Helps balancing the body
Mid brain
Underneath the cerebrum and above pons Functions of mid brain
To control involuntary functions
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Pons
Below mid brain
Functions of pons Control of consciousness
Control level of concentration
Medulla oblongata Lowest part of CNS just above the spinal cord
Functions of Medulla oblongata
Control of respiration Control of circulation
Control of swallowing and vomiting
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Spinal cord Located safely in spinal canal
Length is 45cm, which extends up to firstlumber vertebra
31 pairs of peripheral nerves starts fromspinal cord
Functions of spinal cord To propagate sensory stimuli from organs to
the brain
To carry commands from the brain towardsthe organs
Reflex action
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Reflex action
Protective function of the spinal cord
Sensory organ
Afferent nerve
Sensory cell in posterior horn of spinal cord Connector nerve
Motor cell in anterior horn of spinal cord
Efferent nerve
End organ of reaction
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Autonomic nervous system(Involuntary nervous system) It has control over
Digestion
Respiration
Circulation
Hormone secretion
Maintenance of body temperature
Maintenance of water balance
Peripheral nervous system 12 pairs of cranial nerves from brain (cranial
nerves)
31 pairs of spinal nerves from spinal cord
(spinal nerves)
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Billons of nerve cells
Billons of connections
Maximum utilization of brain is 10%
90 % brain is in dormant state
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Human Anatomy & Physiology
Circulatory System
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Components of blood
Total volume of blood 5 to 6 liters
Components Plasma 55-60 %
Blood cells 40-45 %
RBC
WBC
Platelets
R B C (R d bl d ll )
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R.B.C. (Red blood cells)
Colour of blood due to RBC
4 to 5 millions / c.c. Hemoglobin carry 90% Oxygen
Dumbbell shaped cells with no nucleus
W.B.C. (White blood cells) White colored
6000 to 9000 / c.c.
Kills the bacteria (protective role) No specific shape, with central nucleus
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Platelets
1,00,000 to 2,00,000 / c.c.
Helps in clotting of blood(Enzyme Thrombokinase)
Circular shape
Plasma 90 to 92 % water
8 to 10 % dissolved organic & inorganic
matter (proteins, glucose, salts & hormones) Presence of antibodies
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Functions of Blood To carry Oxygen from lungs to cells and to
carry CO2
from cells to lungs
To carry nutrients from Digestive system tocells
To carry excretory products (waste material)
from cells to excretory organs To carry hormones
To maintain water balance in the body
To maintain body temperature
To protect the body from infections
Clotting the blood after injury
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Difference between Arteries & Veins
Arteries
Carry blood from heartto other organs
Carry oxygenatedblood
Have thick walls
Do not have valves
Veins
Carry blood from otherorgans to heart
Carry de-oxygenatedblood
Have thin walls
Presence of valves
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Heart
Situated in the rib cage of chest on the left
side Embedded in lungs
Size of heart is equal to the size of clenchedfist
Connected with many big (giant )bloodvessels
Made up of involuntary muscle
Heart starts beating from 4th month of IU life.
Duration of one heart beat is 0.8sec.
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4 Chambers of Heart
Auricles to receive blood
Ventricles to pump blood Left side oxygenated blood
Right side deoxygenated blood
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Circulation of Blood
Continuous circulation
Force of circulation due to pumping action ofheart
From left ventricle Aorta Branches &Sub branches Artery Small arteryArteriole Capillaries CELLSVenouls Small veins union of many veins Superior & Inferior venacava Right auricle
Right ventricle Pulmonary arteryLungs (oxygenation) Pulmonary veins Left auricle Left ventricle
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Human Anatomy & Physiology
Respiratory System
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Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Structure and function of the respiratory pumps
How gases are exchanged with blood The role of pressures and surfactants in rate of
exchange
How respiration is regulated
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Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Respiratory System: Overview
Lungs: exchange surface
75 m2
Thin walled
Moist
Ribs & skin protect
Diaphragm & ribs pump air
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Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Respiratory System: Overview
Figure 17-2 b: Anatomy Summary
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Functions
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Functions Supply of Oxygen
To remove CO2 and water vapour
Purification of blood
Protective function- coughing, sneezing
Talking
Organs of Respiration Nose
Throat
Larynx
Trachea with its branching system
lungs
(diagram of Respiratory System)
Nose
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Nose
Two nasal cavities separated by nasal septum
The Nasal Septum is made up of cartilage &bone
Function
Warming of Air Filtration of Air
To keep nasal passage moist
Sensation of smell
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Throat & Larynx
Throat (seven passages)
Larynx Oesophagus
Mouth
Left Eustachian tube
Right Eustachian tube
Left nostril
Right nostril
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Trachea
Made up of cartilage and muscles Two main branches- Left and Right bronchus
Branching and sub branching ending in alveoli
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Inspiration
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Inspiration
Active process by muscular action
Contraction of diaphragm
Increase in vertical diameter
Contraction of intercostals muscles
Elevation of ribs and sternum
Increase in antero-posterior and transverse diameter
Expansion of lungs due to negative pressure
Air drawn inwards Expiration
Passive process
Elastic recoil of the lungs due to Relaxation of diaphragm andinter costal muscle.
Positive pressure created in lungs
Control of Respiration
Control of Inspiration and Expiration by medulla oblongata
L V l
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Lung Volumes
Tidal capacity : 500c.c.
Dead space : 150c.c. Vital capacity : 4500c.c.
Total lung capacity : 6000c.c.
Residual volume : 1350c.c. Expiratory reserve : 1500c.c.
Inspiratory capacity : 3000c.c.
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Analysis of gases in respiration
O2
N2
CO2Inspired air 21% 79% -
Exhaled air 16% 79% 5%
Effects of Pranayama More oxygenation of blood
Improvement in function of all organs
Life span increases because of more supplyof oxygen
F ti f th R i t S t O i
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Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Functions of the Respiratory System: Overview
Figure 17-1: Overview of external and cellular respiration
Exchange O2
Air to blood
Blood to cells
Exchange CO2 Cells to blood
Blood to air
Regulate blood pH Vocalizations
Protect alveoli
The Airways:C d ti f Ai f O t id t Al li
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Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Filter, warm & moisten air
Nose, (mouth), trachea, bronchi & bronchioles
Huge increase in cross sectional area
Conduction of Air from Outside to Alveoli
Figure 17-4: Branching of the airways
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Signal Acquisition
Medical Instrumentation typically entailsmonitoring a signal off the body which isanalog, converting it to an electricalsignal, and digitizing it to be analyzedby the computer.
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Types of Sensors:
Electrodes: acquire an electrical signal
Transducers: acquire a non-electricalsignal (force, pressure, temp etc) andconverts it to an electrical signal
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Active vs Passive Sensors:
Active Sensor: Requires an external AC or DC electrical
source to power the device
Strain gauge, blood pressure sensor
Passive Sensor:
Provides it own energy or derives energyfrom phenomenon being studied Thermocouple
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Sensor Error Sources
Error: Difference between measured value
and true value.
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5 Categories of Errors:1. Insertion Error
2. Application Error
3. Characteristic Error
4. Dynamic Error
5. Environmental Error
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Insertion Error: Error occurring when inserting a
sensor
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Application Error: Errors caused by Operator
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Characteristic Error: Errors inherent to Device
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Dynamic Error: Most instruments are calibrated in static
conditions if you are reading a thermistor ittakes time to change its value. If you readthis value to quickly an error will result.
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Environmental Error: Errors caused by environment
heat, humidity
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Sensor Terminology
Sensitivity:
Slope of output characteristic curve y/ x; Minimum input of physical parameter will
create a detectable output change
Blood pressure transducer may have asensitivity of 10 uV/V/mmHg so you will see a10 uV change for every V or mmHg applied to
the system.
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Input
Output
Input
Output
Which is more sensitive? The left side onebecause youll have a larger change in y for agiven change in x
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Sensor Terminology
Sensitivity Error = Departure from ideal
slope of a characteristic curve
Ideal Curve
Sensitivity Error
Output
Input
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Sensor Terminology
Range = Maximum and Minimum values
of applied parameter that can bemeasured.
If an instrument can read up to 200 mmHgand the actual reading is 250 mmHg then youhave exceeded the range of the instrument.
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Sensor Terminology
Dynamic Range: total range of sensor forminimum to maximum. Ie if your instrumentcan measure from -10V to +10 V your dynamic
range is 20V Precision = Degree of reproducibility denoted
as the range of one standard deviation
Resolution = smallest detectable incrementalchange of input parameter that can bedetected
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Accuracy
Accuracy = maximum difference that
will exist between the actual value andthe indicated value of the sensor
XoXi
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Offset Error
Offset error = output that will exist
when it should be zero
The characteristic curve had the samesensitive slope but had a y intercept
Zero offset errorOffset Error
Input Input
Output Output
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Linearity
Linearity = Extent to which actualmeasure curved or calibration
curve departs from ideal curve.
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Linearity
Nonlinearity (%) = (Din(Max) / INfs) * 100%
Nonlinearity is percentage of nonlinear Din(max) = maximum input deviation
INfs = maximum full-scale input
Input
Output Din(Max)
Full Scale Input
Transducers and other Sensors
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Transducers and other Sensors
Transducers: sensors and are defined asa device that converts energy from someone form (temp., pressure, lights etc) into
electrical energy where as electrodesdirectly measure electrical information
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Wheatstone Bridge
Basic Wheatstone Bridge uses one resistor ineach of four arms where battery excites thebridge connected across 2 opposite resistor
junctions (A and B). The bridge output Eoappears across C and D junction.
Es
R1
R2R4
R3
EC ED+-
A
B
Eo
Eo
R1R3
R2 R4
EC ED
Es
+ -
+ -
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Strain Gauges
Definition: resistive element thatchanges resistance proportional to an
applied mechanical strain
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Strain Gauges
Compression = decrease in length by DL andan increase in cross sectional area.
Rest ConditionL = length
L - DL = length Compression
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Strain Gauges
Tension = increase in length by DL and adecrease in cross section area.
Rest ConditionL = length
TensionL + DL = length
Resistance of a metallic bar is
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Resistance of a metallic bar is
given in length and area
where R = Resistance units = ohms () = resistivity constant unique to type of
material used in bar units = ohm meter (m) L = length in meters (m) A = Cross sectional area in meters2 (m2 )
A
pLR
Resistance of a metallic bar is
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Resistance of a metallic bar is
given in length and area
Example: find the resistance of a copper bar that has a crosssectional area of 0.5 mm2 and a length = 250 mm note the resistivityof copper is 1.7 x 10-8m
- 0085.0
1000
15.0
1000
1250
10*7.12
2
8
mm
mmm
mm
mmm
mA
LR
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Piezoresistivity
Piezoresistivity = change in resistance for agiven change in size and shape denoted as h
Resistance in tension =
Resistance increases in tension
L = length;L = change in L; = resistivityA = Area;A = change in A
DDAALLhR
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Resistance in compression =
Resistance decreases in compression
L = length;L = change in L; = resistivity
A = Area;A = change in A
DDAA
LLhR
Note: Textbook forgot the in equations 6-28 and 6-29 on page 110
Gauge Factor
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Gauge Factor
Gauge Factor (GF) = a method of comparing onetransducer to a similar transducer
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Gauge Factor
where
GF = Gauge Factor unitless
R = change in resistance ohms ()
R = unstrained resistance ohms () L = change in length meters (m) L = unstrained length meters (m)
DD
L
LR
R
GF
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Gauge Factor
Where strain which is unitless GF gives relative sensitivity of a strain gauge where the
greater the change in resistance per unit length thegreater the sensitivity of element and the greater thegauge factor.
LL
RR
GF
D
D
T f St i G U b d d d
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Types of Strain Gauges: Unbonded and
Bonded
Unbonded Strain Gauge: resistanceelement is a thin wire of special alloystretch taut between two flexiblesupports which is mounted on flexiblediaphram or drum head.
Types of Strain Gauges: Unbonded and
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Types of Strain Gauges: Unbonded and
Bonded
When a Force F1 is applied todiaphram it will flex in a manner thatspreads support apart causing anincrease in tension and resistance
that is proportional to the forceapplied.
When a Force F2 is applied todiaphram the support ends will more
close and then decrease the tensionin taut wire (compression force) anddecrease resistance will decrease inamount proportional to applied force
Types of Strain Gauges: Unbonded and
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Types of Strain Gauges: Unbonded and
Bonded
Bonded Strain Gauge:made by cementing athin wire or foil to a diaphragm thereforeflexing diaphragm deforms the element
causing changes in electrical resistance insame manner as unbonded strain gauge
Types of Strain Gauges: Unbonded and
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Types of Strain Gauges: Unbonded and
Bonded
When a Force F1 is applied todiaphram it will flex in amanner that causes anincrease in tension of wirethen the increase in resistanceis proportional to the forceapplied.
When a Force F2 is applied todiaphram that cause a
decrease the tension in tautwire (compression force) thenthe decrease in resistance willdecrease in amountproportional to applied force
Comparison of Bonded vs Unbonded
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Comparison of Bonded vs. Unbonded
Strain Gauges
1. Unbonded strain gauge can be builtwhere its linear over a wide range ofapplied force but they are delicate
2. Bonded strain gauge are linear over asmaller range but are more rugged
Bonded strain gauges are typically usedbecause designers prefer ruggedness.
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Typical Configurations
R2 = SG2R4 = SG4
R3 = SG3
C+
-
A
B
Vo
R1 = SG1
DES
Electrical Circuit MechanicalConfiguration
4 strain gauges (SG) in Wheatstone Bridge:
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Transducer Sensitivity
Transducer Sensitivity = rating thatallows us to predict the output voltagefrom knowledge of the excitation
voltage and the value of the appliedstimulus units = V/V*unit of appliedstimulus
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Transducer Sensitivity
Example if you have a force transducer calibrated ingrams (unit of mass) which allows calibration of forcetransducer then sensitivity denoted as = V/V*g(another ex = V/V*mmHg)
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Transducer Sensitivity
To calculate Output Potential use thefollowing equations:
where Eo = output potential in Volts (V)
E = excitation voltage
= sensitivity V/V*g F = applied force in grams (g)
FEEo **
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Inductance Transducers
Inductance Transducers: inductance L canbe varied easily by physical movement of apermeable core within an inductor 3 basic
forms: Single Coil Reactive Wheatstone Bridge Linear Voltage Differential Transformer LVDT:
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LVDT:
Diaphragm
Core External
Load
L2
L3
L1
Axis of Motion
AC Excitation
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Capacitance Transducers
Quartz Pressure Sensors: capacitivelybased where sensor is made of fusedquartz
Capacitive Transducers: Capacitance Cvaries with stimulus
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Capacitive Transducers:
Three examples: Solid Metal disc parallel to flexible metal
diaphragmseparated by air or vacuum (similar tocapacitor microphone) when force is applied they
will move closer or further away. Stationary metal plate and rotating moveable plate:
as you rotate capacitance will increase or decrease
Differential Capacitance:1 Moveable metal Plateplaced between 2 stationary Places where youhave 2 capacitors: C1 between P1 and P3 and C2between P2 and P3 where when a force is appliedto diaphragm P3 moves closer to one plate or viceversa
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Temperature Transducers
3 Common Types: Thermocouples Thermistors Solid State PN Junctions
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Thermocouple:
Thermocouple: 2 dissimilar conductor joinedtogether at 1 end.
The work functions of the 2 materials are different
thus a potential is generated when junction isheated (roughly linear over wide range)
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Thermistors:
Thermistors: Resistors that change their valuebased on temperature where
Positive Temperature Coefficient (PTC) device willincrease its resistance with an increase intemperature
Negative Temperature Coefficient (NTC) device willdecrease its resistance with an increase intemperature
Most thermistors have nonlinear curve when plottedover a wide range but can assume linearity if within alimited range
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BJT = Bipolar Junction Transistor
Transistor = invented in 1947by Bardeen, Brattain andSchockley of Bell Labs.
IC
VCB
VCE
VBE+
++
-
-
-IB
IE
B = BaseC = CollectorE = Emitter
IE = I B + I C
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BJT = Bipolar Junction Transistor
Transistor rely on the free travel ofelectrons through crystalline solids calledsemiconductors. Transistors usually areconfigured as an amplifier or a switch.
Solid State PN Temperature
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Solid State PN Temperature
Transducers
Solid State PN Junction Diode: thebase emitter voltage of a transistor isproportional to temperature. For adifferential pair the output voltage is:
q
IIKT
VC
C
BE
D2
1ln
K = Boltzmans Constant = 1.38 x10-23J/K
T = Temperature in KelvinIC1 = Collector current of BJT 1 mA
IC2 = Collector current of BJT 2 mA
VCB
VEE-
VBE+
+
+
- -
-VCB
VCC+
VBE
+
ccs1 ccs2
Ic1 Ic2
DVBE