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

2. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Objective
Introduce the basic technique of signal conditioning in process control.

3. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
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.

4. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Principles of Analog Signal Conditioning
Signal-Level and Bias Changes
Linearization
Conversions
Current Signal (4 – 20 mA)
Digital Interface
Filtering & Impedance Matching
Loading Vx Rx Vy
R L
Sensor x

5. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
Divider Circuits
Loading effect of RL
RL >> R2
V S
R 1
V D
R 2
R L

6. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
Divider Circuits
Self-heating (R2 is a temperature sensor)
Example
VS = 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
V S
R 1
V D
R 2

7. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
Bridge Circuits
Wheatstone Bridge
R 1
R 2 D V
R 3
R 4

8. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
Bridge Circuits
Wheatstone Bridge
Galvanometer Detector
Galvanometer
R Th a
R 1
R 2 D
VTh V a b
R G
R 3
R 4 b

9. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
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 a b
R G
R 3
R 4 b

10. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
Bridge Circuits
Wheatstone Bridge
Lead Compensation
R 1
R 2 D V a b
R 3
R 4 c

11. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
Bridge Circuits
Wheatstone Bridge
Current Balance Bridge
R 1
R 2 a D b
R4 >> R5
(R2+R4) >> R5 V
R 4
R 3 I
R 5

12. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
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

13. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
Bridge Circuits
AC Bridges
Z 2
Z 1  D V
Z 3
Z 4

14. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
RC Filters
Low-pass RC Filters R C
V in
V out
Gain 1 ω ω0

15. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
RC Filters
Low-pass RC Filters
Cascaded Stages
R 1
R 2
C 1
C 2
V out
V in
Gain 1 ω ω0
Loading Effect  R2 >> R1, C2 << C1

16. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Example 2.11
A measured signal has a frequency < 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?

17. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Example 2.11
Vout / Vin = 0.01 at 1 MHz
 fc = 10 KHz
Use C = 0.47 μF
 R = 33.9 Ω (too small -> too much current)
Use C = 0.01 μF  R = 1591 Ω
Standard R = 1.5 KΩ
 fc = Hz Vout / Vin =
At 1 KHz: Vout / Vin = 0.996

18. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
RC Filters
High-pass RC Filters C
V in
V out R
Gain 1 ω ω0

19. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Passive Circuits
RC Filters
Band-pass RC Filters
C H
Gain
R L 1
C L
V in
V out
R H ω ω1 ω2
If ω1 << ω2 Then you use the individual equations for the LPF and HPF

20. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Inverting Amplifier
R 2
R 1 − +
V in
V out

21. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Non Inverting Amplifier + −
V in
V out
R 2
R 1 + −
V in
V out = V in

22. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Summing Amplifier
R 1
R 3
V 1 − +
V 2
R 2
V out

23. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Differential Amplifier
R 1
R 2
V 2 − +
R 1
V 1
V out
R 2

24. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Differential Instrumentation Amplifier + −
V 2
R 1
R 2
R 3 − +
R G
R 2
V out
R 1 − +
R 3
V 1

25. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
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

26. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Current-to-Voltage Converter R I − +
V out R

27. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Integrator C R − +
V in
V out

28. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Differentiator R C − +
V in
V out

29. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Power Supply
+V CC
V CC
V in − +
V out t
V CC
−V CC

30. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Power Supply
+V CC
V in − +
V CC
V out t

31. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Power Supply
+V CC − + + −
V CC
V in
½ V CC
V out
½ V CC t

32. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
Operational Amplifiers
Power Supply
+V CC − +
V CC
V out
V in t

33. Analog Signal Conditioning
Princess Sumaya University
Industrial Instruments 1
Analog Signal Conditioning
End of Chapter 2