Digital & Analog ConversionDigital & Analog Conversion
DigitalDigital--toto--Analog Analog Converters(DACsConverters(DACs) )
]222[ 22
11
nnRout bbbVV −−− +++= L
output voltageanalog=outV
voltagereference=RVdbinary worbit -...21 nbbb n =
Rnout VNV2
= input DAC of equivalentnumber whole10 base −=N
nRout VV −=∆ 2
changeoutput smallest =∆ outV
voltagereference=RV
wordin the bits ofnumber =n
RR VVV 9375.0]2222[ 4321max =+++= −−−−
RR VVV 9961.0]22222222[ 87654321max =+++++++= −−−−−−−−
4bit
8bit
Conversion ResolutionConversion Resolution
Generic DAC diagram Typical DAC Circuit
DAC CircuitDAC Circuit
Summing Inverting Amplifier
+−= 2
3
21
1
2 VRRV
RRVout
I1
I3 I2
Is
A
AnalogAnalog--toto--Digital Converters(ADCs)Digital Converters(ADCs)
R
innn V
Vbbb ≤+++ −−− 222 22
11 L
nRVV −=∆ 2
ageinput volt analog=inV voltagereference analog=RV
output digitalbit -...21 nbbb n =
= n
R
in
VVN 2INTRnin VNV
2=
Conversion Resolution
Generic ADC diagramData-acquisition timing diagram Read Operation at any time after the end-of-convert
ADC CharacteristicsADC Characteristics
1. Analog Voltage Input : Signal Input to be Converted2. Power Supply3. Reference Voltage4. Digital Output
N output Lines Connected to Memory Bus5. Control Lines
SC : Start of ConversionEOC : End of ConversionRD : Read
6. Conversion Time
Successive approximation using Internal DAC
Parallel Feedback ADCParallel Feedback ADC
DualDual--Slope ADCSlope ADC
Op amp integrator, comparator, counter. Commonly used in digital voltmeters.Typical timing diagram
∫= dtVRC
V x1
1 xVTRCV 11
1=
∫−= dtVRC
VV R1
12 Rx tVRC
VTRC
V 1112 −=
Rx
x VTtV
1
=
Basic Concept of a sample-and-hold circuit for use with the ADC.
Sampled signal is literally “held”during the ADC conversion
Sample and HoldSample and Hold
ADC interfaced to Computer bus with Tri-state bufferAddress decoding by computer software.
Microprocessor Compatible ADCMicroprocessor Compatible ADC
FrequencyFrequency--based Convertersbased Converters
General diagram of a frequency-based analog-to digital converter.
Common V-to-F Converteruseful in frequency-based ADCs.
Useful for generation of frequencyBy resistance or capacity.
LM331LM331 555 timer555 timer
DAS HardwareDAS Hardware
Figure 3.29Typical layout of a data-acquisition board for use in a personal computer expansion slot.
DATADATA--ACQUISITION SYSTEMSACQUISITION SYSTEMS
Multi-position switch for selecting particular inputs to ADC
Analog MultiplexerAnalog Multiplexer
DAS SoftwareDAS Software
Start ADC-Test EOC-Input
Temperaturehistory
No loading
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No loading Loading
LabViewLabView as DAS Softwareas DAS Software
변태유기소성
t=0
t=t
L01
L02
dL
dl
∆L1 ∆L2
0102
12
LLLL
−∆−∆
=ε
● Power : 50 kW●Maximum temp. : 1500 oC●Maximum load : 90 kgf●Measure of disp. : LVDT &
Laser disp. Sensor● Cooling Method : Gas cooling (Ar)
변태소성 측정장치
FET as an electronic switch.FET as an electronic switch.