3441 Industrial Instruments 1 Chapter 2 Analog Signal Conditioning

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3441Industrial Instruments 1Chapter 2Analog
Signal Conditioning
Princess Sumaya Univ.Electronic Engineering Dept.

• Dr. Bassam Kahhaleh

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Analog Signal Conditioning

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

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Analog Signal Conditioning

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

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Analog Signal Conditioning

• Principles of Analog Signal Conditioning
• Signal-Level and Bias Changes
• Linearization
• Conversions
• Current Signal (4 20 mA)
• Digital Interface
• Filtering ImpedanceMatching
• Loading

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Analog Signal Conditioning

• Passive Circuits
• Divider Circuits
• Loading effect of RL
• RL gtgt R2

V S
R 1
V D
R 2
R L
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Analog Signal Conditioning

• Passive Circuits
• Divider Circuits
• Self-heating (R2 is a temperature sensor)
• Example
• VS 5 V
• R1 10 K O
• 4 KO R2 12 KO
• ? 1.43 V VD 2.73 V
• 0.51 mW PD 0.62 mW

V S
R 1
V D
R 2
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Analog Signal Conditioning

• Passive Circuits
• Bridge Circuits
• Wheatstone Bridge

R 1
R 2
D
V
R 3
R 4
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Analog Signal Conditioning

• Passive Circuits
• Bridge Circuits
• Wheatstone Bridge
• Galvanometer Detector

Galvanometer
R Th
a
R 1
R 2
D
VTh
V
R G
a
b
R 3
R 4
b
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Analog Signal Conditioning

• Passive Circuits
• Bridge Circuits
• Wheatstone Bridge
• Bridge Resolution (Ideal Non ideal Detector)

R Th
a
R 1
R 2
D
VTh
V
R G
a
b
R 3
R 4
b
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Analog Signal Conditioning

• Passive Circuits
• Bridge Circuits
• Wheatstone Bridge
• Lead Compensation

R 1
R 2
D
V
a
b
R 3
R 4
c
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Analog Signal Conditioning

• Passive Circuits
• Bridge Circuits
• Wheatstone Bridge
• Current Balance Bridge

R 1
R 2
a
D
b
R4 gtgt R5 (R2R4) gtgt R5
V
R 4
R 3
I
R 5
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Analog Signal Conditioning

• Passive Circuits
• Bridge Circuits
• Wheatstone Bridge
• Potential Measurement Using Bridges

R 1
R 2
Vc Vx Va
a
c
D
b
V
V x
R 3
R 4
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Analog Signal Conditioning

• Passive Circuits
• Bridge Circuits
• AC Bridges

Z 2
Z 1
D
?
V
Z 3
Z 4
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Analog Signal Conditioning

• Passive Circuits
• RC Filters
• Low-pass RC Filters

R
C
V out
V in
Gain
1
?
?0
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Analog Signal Conditioning

• Passive Circuits
• RC Filters
• Low-pass RC Filters
• Cascaded Stages

R 1
R 2
C 1
V out
C 2
V in
Gain
1
?
?0
Loading Effect ? R2 gtgt R1, C2 ltlt C1
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Analog Signal Conditioning

• Example 2.11
• A measured signal has a frequency lt 1 KHz, but
  there is unwanted noise at about 1 MHz. Design a
  low-pass filter that attenuates the noise to 1.
  What is the effect on the measurement signal at
  it max. of 1 KHz?

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Analog Signal Conditioning

• Example 2.11
• Vout / Vin 0.01 at 1 MHz
• ? fc 10 KHz
• Use C 0.47 µF
• ? R 33.9 O (too small -gt too much current)
• Use C 0.01 µF ? R 1591 O
• Standard R 1.5 KO
• ? fc 10610 Hz Vout / Vin 0.0099995
• At 1 KHz Vout / Vin 0.996

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Analog Signal Conditioning

• Passive Circuits
• RC Filters
• High-pass RC Filters

C
V out
V in
R
Gain
1
?
?0
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Analog Signal Conditioning

• Passive Circuits
• RC Filters
• Band-pass RC Filters

C H
Gain
R L
1
C L
V out
V in
R H
?
?2
?1
If ?1 ltlt ?2 Then you use the individual equations
for the LPF and HPF
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Analog Signal Conditioning

• Operational Amplifiers
• Inverting Amplifier

R 2
R 1
V in
V out
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Analog Signal Conditioning

• Operational Amplifiers
• Non Inverting Amplifier

V in
V out
R 2
R 1
V in
V out V in
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Analog Signal Conditioning

• Operational Amplifiers
• Summing Amplifier

R 1
R 3
V 1
V 2
R 2
V out
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Analog Signal Conditioning

• Operational Amplifiers
• Differential Amplifier

R 1
R 2
V 2
R 1
V 1
V out
R 2
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Analog Signal Conditioning

• Operational Amplifiers
• Differential Instrumentation Amplifier

V 2
R 2
R 3
R 1
R G
R 2
V out
R 1
R 3
V 1
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Analog Signal Conditioning

• Operational Amplifiers
• Voltage-to-Current Converter

R 1
R 2
V in
R 3
R 5
I L
R 4
R L
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Analog Signal Conditioning

• Operational Amplifiers
• Current-to-Voltage Converter

R
I
V out
R
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Analog Signal Conditioning

• Operational Amplifiers
• Integrator

C
R
V in
V out
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Analog Signal Conditioning

• Operational Amplifiers
• Differentiator

R
C
V in
V out
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Analog Signal Conditioning

• Operational Amplifiers
• Power Supply

V CC
V CC
V in
V out
0
t
V CC
-V CC
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Analog Signal Conditioning

• Operational Amplifiers
• Power Supply

V CC
V in
V out
V CC
0
t
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Analog Signal Conditioning

• Operational Amplifiers
• Power Supply

V CC
-
V CC
V in
½ V CC
V out
½ V CC
0
t
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Analog Signal Conditioning

• Operational Amplifiers
• Power Supply

V CC
V CC
V out
V in
0
t
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Analog Signal Conditioning

• End of Chapter 2