3441 industrial instruments 1 chapter 3 digital signal conditioning dr. bassam kahhaleh princess...

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