3441 Industrial Instruments 1 Chapter 2 Analog Signal Conditioning Dr. Bassam Kahhaleh Princess...

34413441Industrial Instruments 1Industrial Instruments 1

Chapter 2Chapter 2

Analog Signal ConditioningAnalog Signal Conditioning

Dr. Bassam KahhalehDr. Bassam Kahhaleh

Princess Sumaya Univ.Princess Sumaya Univ.Electronic Engineering Dept.Electronic Engineering Dept.

Princess Sumaya UniversityPrincess Sumaya University 3441 - Industrial Instruments 13441 - Industrial Instruments 1 22 / 33 / 33


ObjectiveObjective

Introduce the basic technique of signal Introduce the basic technique of signal conditioning in process control.conditioning in process control.



DefinitionDefinition

Signal conditioning refers to operations Signal conditioning refers to operations performed on signals to convert them to a performed on signals to convert them to a form suitable for interface with other form suitable for interface with other elements in the process-control loop.elements in the process-control loop.



Principles of Analog Signal ConditioningPrinciples of Analog Signal Conditioning Signal-Level and Bias ChangesSignal-Level and Bias Changes LinearizationLinearization ConversionsConversions

Current Signal (4 – 20 mA)Current Signal (4 – 20 mA) Digital InterfaceDigital Interface

Filtering & ImpedanceFiltering & ImpedanceMatchingMatching

LoadingLoadingVx

Rx

Vy R L

Sensor x



Passive CircuitsPassive Circuits Divider CircuitsDivider Circuits

Loading effect of RLoading effect of RLL

RRLL >> R >> R22

R 1

R 2 R L

V S

V D



Passive CircuitsPassive Circuits Divider CircuitsDivider Circuits

Self-heating (RSelf-heating (R22 is a temperature sensor) is a temperature sensor)

ExampleExampleVS = 5 V

R1 = 10 K Ω

4 KΩ ≤ R2 ≤ 12 KΩ

1.43 V ≤ VD ≤ 2.73 V

0.51 mW ≤ PD ≤ 0.62 mW

R 1

R 2

V S

V D



Passive CircuitsPassive Circuits Bridge CircuitsBridge Circuits

Wheatstone BridgeWheatstone Bridge

R 1 R 2

R 3

V D

R 4

VRR

RV

RR

RV

42

4

31

3

3241 RRRR




Wheatstone BridgeWheatstone BridgeGalvanometer DetectorGalvanometer Detector

R 1 R 2

R 3

V D

R 4

VTh

R Th

a b

a

b

R G

Galvanometer




Wheatstone BridgeWheatstone BridgeBridge Resolution (Ideal & Non ideal Detector)Bridge Resolution (Ideal & Non ideal Detector)

R 1 R 2

R 3

V D

R 4

VTh

R Th

a b

a

b

R G




Wheatstone BridgeWheatstone BridgeLead CompensationLead Compensation

R 1 R 2

R 3

V D

R 4

a b

c




Wheatstone BridgeWheatstone BridgeCurrent Balance BridgeCurrent Balance Bridge

R 1 R 2

R 3

V D

R 4

ab

R 5I

R4 >> R5

(R2+R4) >> R5

5542

54

31

3 )(RIV

RRR

RRV

RR

RV




Wheatstone BridgeWheatstone BridgePotential Measurement Using BridgesPotential Measurement Using Bridges

R 1 R 2

R 3

V D

R 4

ab

Vc = Vx + Va

042

4

31

3

V

RR

RV

RR

RVx

cV x

0)(

5542

54

31

3

RIVRRR

RRV

RR

RVx




AC BridgesAC Bridges

Z 1Z 2

Z 3

V D

Z 4

3241 ZZZZ



Passive CircuitsPassive Circuits RCRC Filters Filters

Low-pass Low-pass RCRC Filters Filters

)2/(1 CRfc

R

C V outV in

2

1

1

c

in

out

ffV

V

ω

Gain

ω0

1




Low-pass Low-pass RCRC Filters Filters

Cascaded StagesCascaded Stages

R 1

C 1 V outV in

ω

Gain

ω0

1

C 2

R 2

)2/(1 CRfc

2

1

1

c

in

out

ffV

V

Loading Effect R2 >> R1, C2 << C1



Example 2.11Example 2.11

A measured signal has a frequency < 1 KHz, A measured signal has a frequency < 1 KHz, but there is unwanted noise at about 1 MHz. but there is unwanted noise at about 1 MHz. Design a low-pass filter that attenuates the Design a low-pass filter that attenuates the noise to 1%. What is the effect on the noise to 1%. What is the effect on the measurement signal at it max. of 1 KHz?measurement signal at it max. of 1 KHz?



Example 2.11Example 2.11Vout / Vin = 0.01 at 1 MHzVout / Vin = 0.01 at 1 MHz

ffcc = 10 KHz = 10 KHz

Use C = 0.47 Use C = 0.47 μμFF R = 33.9 R = 33.9 ΩΩ (too small -> too much current)(too small -> too much current)

Use C = 0.01 Use C = 0.01 μμFF R = 1591 R = 1591 ΩΩStandard R = 1.5 KStandard R = 1.5 KΩΩ

ffcc = 10610 Hz = 10610 Hz Vout / Vin = 0.0099995Vout / Vin = 0.0099995

At 1 KHz:At 1 KHz: Vout / Vin = 0.996Vout / Vin = 0.996




High-pass High-pass RCRC Filters Filters

)2/(1 CRfc R

C

V outV in

2

1

c

c

in

out

ff

ff

V

V

ω

Gain

ω0

1




Band-pass Band-pass RCRC Filters Filters

R H

C H

V out

R L

C LV in

ω

Gain

ω2

1

ω1

If ω1 << ω2 Then you use the individual equations for the LPF and HPF



Operational AmplifiersOperational Amplifiers Inverting AmplifierInverting Amplifier

V out

R 1

V in

−

+

R 2

1

2

R

R

V

V

in

out



Operational AmplifiersOperational Amplifiers Non Inverting AmplifierNon Inverting Amplifier

V out

R 1

V in

+

−

R 2

1

21

R

RR

V

V

in

out

V out = V in

V in+

−



Operational AmplifiersOperational Amplifiers Summing AmplifierSumming Amplifier

V out

R 2

V 1

−

+

R 1

2

2

31

1

3V

R

RV

R

RVout

R 3

V 2



Operational AmplifiersOperational Amplifiers Differential AmplifierDifferential Amplifier

V out

R 2

V 2

−

+

R 1

)( 211

2VV

R

RVout

R 2

V 1

R 1



Operational AmplifiersOperational Amplifiers Differential Instrumentation AmplifierDifferential Instrumentation Amplifier

V out

R 3

V 2

−

+

R 2

)(2

1 211

21VV

R

R

R

RV

Gout

R 3

V 1

R 2

−

+

+

−R 1

R 1

R G



Operational AmplifiersOperational Amplifiers Voltage-to-Current ConverterVoltage-to-Current Converter

I L

R 3

−

+

R 1

inL VRR

RI

31

2

R 2

V in

R 4

R 5

R L

42531 )( RRRRR



Operational AmplifiersOperational Amplifiers Current-to-Voltage ConverterCurrent-to-Voltage Converter

I−

+

R

R

V outIRVout



Operational AmplifiersOperational Amplifiers IntegratorIntegrator

V out

R

V in

−

+

C dtV

RCV inout

1



Operational AmplifiersOperational Amplifiers DifferentiatorDifferentiator

V out

R

V in

−

+

C

dt

dVRCV

inout



Operational AmplifiersOperational Amplifiers Power SupplyPower Supply

V out

V in−

+

V CC

V CC

t0

+V CC

−V CC




V out

V in−

+V CC

t

+V CC

0




V out

V CC

t

+V CC

0

V in

−

+

½ V CC

½ V CC

+

−




V out

V CC

t

+V CC

0

V in

−

+


End of Chapter 2End of Chapter 2


3441 Industrial Instruments 1 Chapter 2 Analog Signal Conditioning Dr. Bassam Kahhaleh Princess...

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Transcript of 3441 Industrial Instruments 1 Chapter 2 Analog Signal Conditioning Dr. Bassam Kahhaleh Princess...