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學(xué)20生13物-2醫(yī)01學(xué)4學(xué)電年子第學(xué)一學(xué)期生物醫(yī)學(xué)喬清理2013,08,28主要內(nèi)容電測(cè)量的優(yōu)點(diǎn)生物醫(yī)學(xué)測(cè)量系統(tǒng)的一般結(jié)構(gòu)生物醫(yī)學(xué)測(cè)量的特點(diǎn)(或約束)對(duì)測(cè)量系統(tǒng)的基本要求生物醫(yī)學(xué)測(cè)量趨勢(shì)測(cè)控系統(tǒng)的設(shè)計(jì)1.測(cè)量的概念與分類獲取傳輸處理控制…信息獲取是了解信息流組成,
疾病重要的的一環(huán)。測(cè)量的定義測(cè)量是為確定被測(cè)對(duì)象的量值而進(jìn)行的實(shí)驗(yàn)過程。測(cè)量結(jié)果=測(cè)量數(shù)值*測(cè)量單位即:X=X0
*{X}廣義測(cè)量的定義廣義地講,測(cè)量不僅對(duì)被測(cè)的物理量進(jìn)行定量的測(cè)量,而且還包括對(duì)更廣泛的被測(cè)對(duì)象進(jìn)行定性、定位的測(cè)量。而測(cè)量結(jié)果也不僅僅是由量值和單位來表征的一維信息,還可以用二維或 的圖形、圖像來顯示被測(cè)對(duì)象的屬性特征、空間分布、 結(jié)構(gòu)等。根據(jù)所測(cè)量的參數(shù),測(cè)量分為電量測(cè)量和非電量測(cè)量電量測(cè)量:心電信號(hào),直接由電極拾??;非電量測(cè)量:血壓、體溫、呼氧等都需要通過各種傳感器拾取,然后轉(zhuǎn)換為與之有確定函數(shù)關(guān)系的電信號(hào)測(cè)量的分類2.電測(cè)法的優(yōu)點(diǎn)具有極精細(xì)的分辨力和很寬的測(cè)量范圍。采取電子技術(shù),可以很方便地改變儀器的靈敏度和測(cè)量范圍。電子測(cè)量?jī)x器具有極小的慣性。既能測(cè)量變化緩慢的量,又可測(cè)量快速變化的量。有利于信息傳遞。無論在時(shí)間上還是在空間上可以很方便地實(shí)現(xiàn)遙測(cè)。靈活的變化技術(shù)和各種運(yùn)算和處理、顯示和記錄。。PerceptibleoutputOutputdisplayControlAndfeedbackCPUDatatransmissionDatastorageSignalConditiongSensorMeasurandRadiation,electric
current,or
otherappliedenergyCalibrationsignalPowersource3生物醫(yī)學(xué)測(cè)量系統(tǒng)的構(gòu)成原理框圖A/D生物醫(yī)學(xué)測(cè)量系統(tǒng)的構(gòu)成傳感器:非電量到電量的變換;
信號(hào)調(diào)理電路:阻抗變換,放大,濾除噪聲,抗混頻;動(dòng)態(tài)范圍匹配A/D轉(zhuǎn)換:微處理器:信號(hào)處理,系統(tǒng)控制D/A轉(zhuǎn)換:MeasurandThe
object
of
a
measurement;The
measurand
is
the
desired
input
and
the
object
of
measurement.The ty,
property,
or
condition
that
is
measured
by
aninstrumentation
systemis
called
the
measurandMeasurand
can
be
a
bioelectric
signal,
such
as
those
generated
bymuscles
or
the
brain,
or
a
chemical
or
mechanical
signal
that
isconverted
to
an
electrical
signal.BiopotentialPressureFlowDimensions
(imaging)Displacement
(velocity,
acceleration,
force)ImpedanceTemperatureChemical
ConcentrationBiomedical
MeasurandMeasurementRangeFrequency,
HzMethodBlood
flow1
to
300
mL/s0
to
20Electromagnetic
orultrasonicBlood
pressure0
to
400
mmHg0
to
50Cuff
or
strain
gageCardiac
output4
to
25
L/min0
to
20Fick,
dye
dilutionElectrocardiography0.5
to
4
mV0.05
to150Skin
electrodesElectroencephalography5
to
300
V0.5
to
150Scalp
electrodesElectromyography0.1
to
5
mV0
to
10000Needle
electrodesElectroretinography0
to
900
V0
to
50Contact
lens
electrodespH3
to
13
pH
units0
to
1pH
electrodepCO240
to
100mmHg0
to
2pCO2
electrodepO230
to
100mmHg0
to
2pO2
electrodeP
otachography0
to
600
L/min0
to
40P
otachometerRespiratory
rate2
to
50breaths/min0.1
to
10ImpedanceTemperature32
to
40
°C0
to
0.1ThermistorPerceptibleoutputOutputdisplayControlAndfeedbackCPUDatatransmissionDatastorageSignalConditiongSensorMeasurandRadiation,electric
current,or
otherappliedenergyCalibrationsignalPowersource生物醫(yī)學(xué)測(cè)量系統(tǒng)的構(gòu)成原理框圖A/DSensor
and
TransducerTransducerA
device
that
converts
a
signal
from
one
physical
form
to
acorresponding
signal
having
a
different
physical
formPhysical
form:
mechanical,
thermal,
magnetic,
electric,
optical,chemical…Transducers
are
ENERGY
CONVERTERS
or
MODIFIERSSensorA
device
that
receives
and
responds
to
a
signal
or
stimulusThis
is
a
broader
concept
that
includes
the
extension
of
our
perceptiontiescapabilities
to
acquire
information
about
physicalTransducers:
sensors
and
actuatorsSensor:
an
input
transducer
(i.e.,
a
microphone)Actuator:
an
output
transducer
(i.e.,
a
loudspeaker)Signal
ConditioningAmplifier:electronic
amplifier
amplifies
the
output
of
the
primary
transducer
orvariable
conversion
element,
thus
improving
the
sensitivity
andresolution
of
measurement.
This
element
of
a
measuring
system
isparticularly
important
where
the
primary
transducer
has
a
low
output.For
example,
EEG
electrodes
have
a
typicaloutput
of
only
a
fewmillivolts.FilterA
device
or
program
that
separates
data,
signals,
or
material
inaccordance
with
specified
criteria.Impedance
matchogto
Digital
(A/D/A)Average
(reduce
noise)Time
→
Frequency
(Spectrumysis)A/DTheReal
World
is
ogAn
og-to-digital
converter
(abbreviated
ADC,
A/D
or
Ato
D)
is
an
electronic
integrated
circuit
(i/c)
that
convertscontinuous
signals
to
discrete
digital
numbers.
The
reverseoperation
is
performed
by
a
digital-to-
og
converter
(DAC).CPU:Signal
processing:Average
(reduce
noise)Time
→
Frequency
(SpectrumSystem
controlUser
interfaceysis)Output
Display?numerical
or
graphical,
discrete
or
continuous,permanent
or
temporary,
visual
orauditoryHuman
factors
engineering
guidelines
andpreferred
practices
for
the
design
of
medicaldevices
(AAMI,
1993)Auxiliary
ElementsCalibration
signal
(known
voltage)control
and
feedback
(insulin
delivery)alarms
(intensive
care
monitors)transmission
of
data
to
remo ocations
(nursesstations)4
對(duì)測(cè)量系統(tǒng)的基本要求穩(wěn)定性穩(wěn)定性就是指系統(tǒng)動(dòng)態(tài)過程的振蕩傾向及其恢復(fù)平衡狀態(tài)的能力。對(duì)于穩(wěn)定的系統(tǒng),當(dāng)輸出量偏離平衡狀態(tài)時(shí),應(yīng)能隨著時(shí)間收斂并且最后回到初始的平衡狀態(tài)。精確性一般以穩(wěn)態(tài)誤差來衡量。所謂穩(wěn)態(tài)誤差是指以一定變化規(guī)律的輸入信號(hào)作用于系統(tǒng)后,當(dāng)調(diào)整過程結(jié)束而趨于穩(wěn)定時(shí),輸出量的實(shí)際值與期望值之間的誤差值,它反映了動(dòng)態(tài)過程后期的性能。這種誤差一般是很小的??焖傩钥焖傩允侵府?dāng)系統(tǒng)的輸出量與輸入量之間產(chǎn)生偏差時(shí),消除這種偏差的快慢程度??焖傩院玫南到y(tǒng),它消除偏差的過渡過程時(shí)間就短,就能復(fù)現(xiàn)快速變化的輸入信號(hào),因而具有較好的動(dòng)態(tài)性能。安全5
Medical
measurement
constraintsMeasurement
range
are
qui ow(測(cè)量范圍窄)Most
voltages
are
in
the
micro-volt(μV)range.Low
pressures
(about
100
mm
Hg
=
1.93
psi
=13.3
kPa)Low
frequency
(from
dc
to
1
kHz)Many
crucial
variables
in
living
system
are
inaccessible
(must
bemeasured
indirectly,
ex.ECG)Inherent
variability:
Variables
measured
from
the
human
or
animalsare
seldom
deterministic.Vary
with
timeVary
among
the
patientsInterference
from
other
physiological
systemsComplex
feedbackEnergy:
X-ray,
ultrasonic
imaging,
electromagnetic,
Dopplerultrasonic
blood
flow-metersOperation:Equipment
must
be
reliable,
simple
to
operate,
and
capable
ofwithstanding
physical
abuse
and
exposure
to
corrosive
chemicals.Minimize
electric-shock
hazards6
Six
major
Trends
of
MD
TechnologyComputer-related
technology:
Robotic
SurgeryMolecular
medicine:BiochipHome-
and
self-care
products:
GlucoWatchMinimally
invasive
procedures:SwallowableCamera
PillCombination
device/drug
products:Organ
substitute
and
assist
devices:Trends
in
Medical
ElectronicsIncreasing
use
in
the
homeHigher
portability
for
sophisticated
imaging
andmonitoringUltrasoundPatient
monitors
Increasing
miniaturization
for
implantable
deviceswithvery
long
servicelivesConvergence
of
functionsWireless
and
connected
solutions
for
monitoringExplosive
growth
predicted
forChina, and
otheremerging
countries6
測(cè)控系統(tǒng)的設(shè)計(jì)自上而下(top-downapproaches):起始點(diǎn)是模擬電子系統(tǒng)所需求的整體性能分析,設(shè)計(jì)以集成運(yùn)算放大器。自下而上(Bottom
to
up):從基本固體物理開始,講授二極管和三極管等半導(dǎo)體器件的功能。通過實(shí)例介紹電壓放大器的三極管使用。使用三極管如何配置不同的放大器。然后,學(xué)習(xí)集成放大器。測(cè)控系統(tǒng)的設(shè)計(jì)需求分析與描述,和確定性能指標(biāo)(參數(shù)確定):被測(cè)量的量是什么?信號(hào)的大小與頻率?系統(tǒng)的測(cè)量的精度?系統(tǒng)的使用條件。及其它一些系統(tǒng)所具有的功能,如信號(hào)的顯示、記錄、功能。系統(tǒng)的成本、設(shè)計(jì)或研發(fā)的時(shí)間。工藝條件。提出和確定實(shí)現(xiàn)的方案(結(jié)構(gòu)確定):結(jié)構(gòu)分解性能指標(biāo)分配:確定前向信號(hào)通道(指從傳感器到模數(shù)轉(zhuǎn)換器的模擬信號(hào)放大、處理部分電路)所需信號(hào)放大、濾波或變換電路的級(jí)數(shù),各級(jí)的增益,濾波器的階數(shù)、形式和截止頻率等。確定各個(gè)組成部分的具體設(shè)計(jì)。DESIGN
CRITERIASignal
factors:
sensitivity,
range,
inputimpedance,
accuracy,
linearity,
reliability,…Environment
factors:
SNR,
power,
size,
shape,stability,….Medical
factors:
invasive
or
non-invasivematerialtoxicity,
radiation,
…Economic
factors:
cost,
availability,warranty,consumable
requirements,….生物醫(yī)學(xué)測(cè)量的特點(diǎn)(或約束)MeasurementRangeFrequency,
HzMethodBlood
flow1
to
300
mL/s0
to
20Electromagnetic
or
ultrasonicBlood
pressure0
to
400
mmHg0
to
50Cuff
or
strain
gageCardiac
output4
to
25
L/min0
to
20Fick,
dye
dilutionElectrocardiography0.5
to
4
mV0.05
to
150Skin
electrodesElectroencephalography5
to
300
V0.5
to150Scalp
electrodesElectromyography0.1
to
5
mV0
to
10000Needle
electrodesElectroretinography0
to
900
V0
to
50Contact
lens
electrodespH3
to
13
pHunits0
to
1pH
electrodepCO240
to
100
mmHg0
to
2pCO2
electrodepO230
to
100
mmHg0
to
2pO2
electrodeP
otachography0
to
600
L/min0
to
40P
otachometerRespiratory
rate2
to
50
breaths/min0.1
to
10ImpedanceTemperature32
to
40
°C0
to
0.1Thermistor生物醫(yī)學(xué)測(cè)量的特點(diǎn)(或約束)SpecificationValueInputsignal
dynamic
range±5
mVDc
offset
voltage±300mVSlewrate320
mV/sFrequency
response0.05
to
150
HzInput
impedance
at
10
Hz2.5
MDclead
current0.1
Return
time
after
leadswitch1sOverload
voltage
without
damage5000VRisk
current
at
120
V10
Table Specification
values
for
an
electrocardiograph
are
agreed
uponby
a
committee.生物醫(yī)學(xué)測(cè)量的特點(diǎn)(或約束)與其它測(cè)量系統(tǒng)相比,生物醫(yī)學(xué)測(cè)量有以下特點(diǎn):從測(cè)量值范圍上,測(cè)量的生理參數(shù)的幅值和頻率范圍都是比較低的。從測(cè)量對(duì)象上,由于測(cè)量對(duì)象是人,有生命的。被測(cè)量是動(dòng)態(tài)的。許多被測(cè)生理量的很難接近。被測(cè)量是很少是確定的,測(cè)量結(jié)果是隨機(jī)的。生理數(shù)據(jù)的時(shí)間變異性和
差異性。生理系統(tǒng)間存在相互的相用,系統(tǒng)間相互聯(lián)系缺乏了解。傳感器對(duì)被測(cè)生理量的影響Simple
Instrument
ModelThe
key
functional
element
of
the
instrument
model
is
thesensor,
which
has
the
function
of
converting
theph
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