3441 industrial instruments 1 chapter 3 digital signal conditioning dr. bassam kahhaleh princess...
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34413441Industrial Instruments 1Industrial Instruments 1
Chapter 3Chapter 3
Digital Signal ConditioningDigital Signal Conditioning
Dr. Bassam KahhalehDr. Bassam Kahhaleh
Princess Sumaya Univ.Princess Sumaya Univ.Electronic Engineering Dept.Electronic Engineering Dept.
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Digital Signal ConditioningDigital Signal Conditioning
ObjectiveObjective
Introduce the basic technique of digital Introduce the basic technique of digital signal conditioning, especially interfacing, in signal conditioning, especially interfacing, in process control.process control.
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Digital Signal ConditioningDigital Signal Conditioning
Digital SignalsDigital Signals
Level
Pressure
Temperature
pressureLow
pressureHighB
0
1
levelLow
levelHighA
0
1
.
.
0
1
tempLow
tempHighC
CBACABAAlarm
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Digital Signal ConditioningDigital Signal Conditioning
Digital SignalsDigital Signals
TTL OutputTTL Output Totem-poleTotem-pole Tri-stateTri-state Open-collectorOpen-collector
I H = 0.04 mA
Low
High
Volt
VoltsV
8.00
54.2
I L = 1.6 mA
I H = 0.4 mA
I L = 16 mA
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Digital Signal ConditioningDigital Signal Conditioning
TTL InterfacingTTL Interfacing
Never leave inputs unconnectedNever leave inputs unconnected
Never short-circuit outputs to ground or VccNever short-circuit outputs to ground or Vcc
Never short-circuit outputs together unless they Never short-circuit outputs together unless they are tri-state or open-collector outputsare tri-state or open-collector outputs
Never use pull-down resistorsNever use pull-down resistors
Be careful when using different power supplies Be careful when using different power supplies (V(VCC1CC1 = +5, V = +5, VCC2CC2 = +12). = +12).
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Digital Signal ConditioningDigital Signal Conditioning
TTL InterfacingTTL Interfacing
IR
What is the minimum resistance value?
When the tri-state output is floating:
V should be max 0.8, IR = 1.6 mA
R = 0.8 / 1.6 = 0.5 KΩ
V
Now what happens when the tri-state output goes high?
V should be min 2.4 V, therefore IR = 2.4 / 0.5 K = 4.8 mA !!
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Digital Signal ConditioningDigital Signal Conditioning
TTL InterfacingTTL Interfacing
IR
Typically, R = 10 KΩ
IR max = (5 – 0.2) / 10 = 0.48 mA
V
+VCC
Now what is the value of V when the tri-state outputs goes floating?
IR = 0.04 mA V = 5 – 0.04 x 10 = 4.6 Volts
+VCC
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Digital Signal ConditioningDigital Signal Conditioning
TTL InterfacingTTL Interfacing
IR
LED:
V = 1.5 ~ 1.6 V
I = 10 ~ 15 mA
+VCC
Standard TTL gates should not source such current to a LED, but it can sink it.
What is the minimum value of R?
VO max = 0.8 V, IR = 15 mA
R = (5 – 1.5 – 0.8) / 15 = 0.18 KΩ
Typically, VO max = 0.2 V, IR = 15 mA, R = 220 Ω
Vo
R
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Digital Signal ConditioningDigital Signal Conditioning
TTL InterfacingTTL Interfacing
IR
+VCC2
VCC2 > VCC1
Vo
R
+VCC1
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Digital Signal ConditioningDigital Signal Conditioning
TTL InterfacingTTL Interfacing
NC
NO+ 12 V
R
Relay current = 40 mA
β = 100
IB = 0.4 mA
R = (2.4 – 0.7) / 0.4
= 4.25 KΩ
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
ComparatorsComparators
Alarm
+
−
+
−
0.352 V
2.0 V
2.2 mV/°C
0.2 V / kPa
T
P
Comparators’ Power Supply?
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
Hysteresis ComparatorsHysteresis Comparators
+
−
R
R f
Vin
Vref
Vout
VL
VO
Vout
0
VH
Vin
Of
refL
refH
VR
RVV
VV
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
Digital-to-Analog Converters (DAC)Digital-to-Analog Converters (DAC)
Bipolar DAC
refnout VN
V2
Rrefnout VVN
V2
1
2
Conversion Resolution?
refnout VV2
1
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
R-2R ladderR-2R ladder
DACDACV out
R
VR
−
+
R
b0
b1
b2
b3
RR
2R2R 2R 2R 2R
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
R-2R ladderR-2R ladder
DACDACV out
R−
+
R
RR
2R2R 2R 2R 2R
VR
VTH
RTH = R
= ½ VR
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
R-2R ladderR-2R ladder
DACDACV out
R−
+
R
RR
2R 2R 2R½ VR
R
VTH
RTH = R
= ¼ VR
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
Analog-to-Digital Converters (ADC)Analog-to-Digital Converters (ADC)
Bipolar ADC
R
inn
V
VINTN 2
Conversion Resolution?
RnVV
2
1
2
12
R
inn
V
VINTN
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
Parallel Feedback ADCParallel Feedback ADC
Logic CountingNetwork
DAC
Comparator
VX
...
bn-1
bn-2
b1
b0
SC
EOC
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
Ramp ADC (Dual-Slope)Ramp ADC (Dual-Slope)
DigitalCounter
Logic Control
Comparator
−VX
bn-1
bn-2
b1
b0
SCEOC
−
++VR
R
C
T1
VO
V1
0t x
t
VO
dtVRC
V X1
1 RX
X VT
tV
1
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
Conversion-Time ConsequencesConversion-Time Consequences
CnR
C
i VV
dt
dV
2
C
Vi
t
VN
VN+1
)cos(
)sin(
tVdt
dV
tVV
Pi
Pi
PCn
R
V
V
2
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Digital Signal ConditioningDigital Signal Conditioning
ConvertersConverters
Sample-and-Hold (S/H)Sample-and-Hold (S/H)
+
−ADC
C
Vin(t)
S/H
Vc(t)
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End of Chapter 3End of Chapter 3
Digital Signal ConditioningDigital Signal Conditioning