Architecture of Smart Sensors.ppt

Architecture of Smart Sensors, Essential parts, Signal Conditioners, Filtering, Converters

1. Dr.T.Mrunalini
AP (SrG), EIE, KEC
Architecture of Smart Sensors

2. Block Diagram of Smart Sensor

3. Features of Smart Sensors
AutomaticRangingandcalibrationofdatathroughbuild-in
system
DataAcquisitionsystem(DAS)andstorage
Automaticlinearizationofnonlineartransferfunctions
Autocorrectionofoffsets,temperaturecompensation
Selftuningcontrolalgorithms
Communicatesthroughserialbus
Remotemonitoring,multisensingandremote
configurationofdevices

4. Architecture of Smart sensor

5. Important Components
Sensing element and Transduction element
Interfacing Hardware/ Data Acquisition System
(DAS)
Signal Conditioning Devices
Conversion Devices
Filters
Programming Devices (Processors)
Communication Interfaces

6. Signal Conditioning
Analogsignalsneedtobecorrectlypreparedbefore
theycanbeconvertedintodigitalformforfurther
processing.
Signalconditioningisanelectroniccircuitthat
manipulatesasignalforthenextstageofprocessing.
Manydataacquisitionapplicationsinvolve
environmentalormechanicalmeasurementfrom
sensors,Examples:temperatureandvibration.
Sensorsrequiresignalconditioningbeforeadata
acquisitiondevicecaneffectivelyandaccurately
measurethesignal.

7. Signal Conditioner Types
Voltage and high-voltage signal conditioners
Current signal conditioners
IEPE signal conditioners (or ICP/piezoelectricsignal
conditioners)
Charge signal conditioners
Strain gauge signal conditioners
Load cell signal conditioners
Thermocouple signal conditioners
RTDsignal conditioners
Thermistorsignal conditioners
LVDT signal conditioners
AC signal conditioning
DC signal conditioning
Digital signal conditioners

8. Requirements of Signal Conditioner
Therequiredelementsofsignalconditionersare
Electricalisolation
Therightconnectorsforsensorconnections
Measurementrangeselection
Signalfiltering(e.g.anti-aliasingfiltering)
Conformancewithsensorrequirements.

9. Signal Filtering
Asidefromsettingtheinputgain,themostimportant
functionofasignalconditioneristoprovidefiltering.
Attheveryleast,atwoorfour-polelow-passfilterisoften
neededtosuppressorreduceelectricalnoise,whichcan
getintothesignalfromthetestingenvironment.
Anti-aliasingfilters(AAF)preventwrongreadingsby
automaticallyadjustingthefront-endfilteraccordingto
theselectedsamplerate

13. Converters
ConvertersandExpandersallowstoconnectothertypes
ofbusesorinterfacestostandardmonitoringHWgroup
devices.
Theoutputcanbeacontinuousvalue,anextensionofthe
numberofDIinputsorDOoutputs.
SignalConverter:Convertssignalsfromsensorsto
industrialcurrentsignals,convertsanaloginputsignalsto
analogoutputsignals,normalizessignals,orisolates
signals.

14. A/D Converters
AnA/Dconverterisadevicethatconvertsanalog
signals(usuallyvoltage)obtainedfromenvironmental
(physical)phenomenaintodigitalformat
Conversioninvolvesaseriesofsteps,including
sampling,quantization,andcoding.
Electricallysophisticatedandhigh-speedprocessing
areperformeddigitallyinCPUsandDSPs.

15. Operation of A/D Converters

16. TheA/Dconverterbreaksup(samples)theamplitudeof
theanalogsignalatdiscreteintervals,whicharethen
convertedintodigitalvalues.
Theresolutionofananalogtodigitalconverteris
typicallyexpressedbythenumberofbits.
Intheabovecaseofa3bitA/Dconverter,theuppervalue
(b2)isreferredtoastheMostSignificantBit(MSB)and
thelowestvalue(b0)theLeastSignificantBit(LSB).

17. Thegraphbelowshowstherelationship
betweentheanaloginputanddigitaloutput

18. Analog Signal to Digital Signal Conversion
Methods
Sampling:Theprocessoftakingamplitudevaluesofthe
continuousanalogsignalatdiscretetimeintervals
(Sampling Period Ts).
Sampling Period Ts = 1/Fs (Sampling Frequency)
SamplingisperformedusingaSampleandHold(S&H)
circuit.
Quantization:involvesassigninganumericalvalueto
eachsampledamplitudevaluefromarangeofpossible
valuescoveringtheentireamplituderange(basedonthe
numberofbits).
Coding:Oncetheamplitudevalueshavebeenquantized
theyareencodedintobinaryusinganEncoder.

20. THANK YOU