1. 3442 Industrial Instruments 2 Chapter 7 Final Control
Princess Sumaya University
Industrial Instruments 2
Princess Sumaya Univ. Electronic Engineering Dept.
3442 Industrial Instruments 2 Chapter 7 Final Control
Dr. Bassam Kahhaleh
Dr. Bassam Kahhaleh

2. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Objective
The function of the final control element is to translate low-energy control signals into a level of action commensurate with the process under control.

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Industrial Instruments 2
7: Final Control
Operation
Block Diagram
Signal
Conversions
Actuator
Control
Signal
Final
Control
Element
Process

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Industrial Instruments 2
7: Final Control
Operation
Block Diagram
Signal
Conversions
Actuator
Control
Signal
The devices that perform such signal conversions are often called transducers because they convert control signals from one form to another, such as current to pressure, current to voltage … etc.
Final
Control
Element
Process

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Industrial Instruments 2
7: Final Control
Operation
Block Diagram
Signal
Conversions
Actuator
Control
Signal
Final
Control
Element
The actuator is a translation of the (converted) control signal into action on the control element.
Process

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Industrial Instruments 2
7: Final Control
Operation
Block Diagram
Signal
Conversions
Actuator
Control
Signal
Final
Control
Element
The control element is operated (run) by the actuator.
Process

7. 3442 - Industrial Instruments 2
Princess Sumaya University
Industrial Instruments 2
7: Final Control
Operation
Block Diagram
Signal
Conversions
Actuator
Control
Signal
Final
Control
Element
The process is operation (objective) under control.
Process

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Industrial Instruments 2
7: Final Control
Operation
Example: Baking of Crackers

9. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Relays
Mechanical
Solid-State
Amplifiers
Transistor
Op-amp

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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Relays
Mechanical

11. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Relays
Mechanical

12. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Relays
Mechanical

13. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Op-amp
Example:
Convert a “4 – 20” mA control signal to a “5 – 10” V signal.
I (mA)
V (Volts) 5 10
Solution:
Vin = Rin * Iin
Vout = K Vin + VB

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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Op-amp
Solution:
Vin = Rin * Iin
Let Rin = 100 Ω
Vin (V)
Vout (V) 5 10

15. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Op-amp
Solution:
Vout = K Vin + VB
5 = K * VB
10 = K * 2 + VB
K = 3.125
VB = 3.75
Vout = Vin
Vout = (Vin + 1.2)
Vin (V)
Vout (V) 5 10

16. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Analog Electrical Signals
Op-amp
Solution:
Vout = (Vin + 1.2)

17. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Digital Electrical Signals
Op-amp
DAC
Direct Action
Example:
A 4-bit digital word is intended to control the setting of a 2-Ω DC resistive heater. Heat output varies as a 0 – 24 V input to the heater. Using a 10–V DAC followed by an amplifier and a unity gain high-current amplifier, calculate: a) the settings from minimum to maximum heat dissipation, and b) how the power varies with LSB changes.

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Industrial Instruments 2
7: Final Control
Signal Conversions
Digital Electrical Signals
DAC
Solution:
DAC 10–V reference  24 = 16
Therefore:
1111  (15/16) * 10 = V .
0000  0 V
Amplifier gain = 24 / = 2.56
Incremental step = [(1/16) * 10 ] * 2.56 = 1.6 V
ΔV = (1/16) * 10 V

19. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Digital Electrical Signals
DAC
Power (W)
Solution:
ΔP (from 0000 to 0001)
= (1.6 V)2 / 2 Ω
= 1.28 W
ΔP (from 1110 to 1111)
= (24)2 – (22.4)2 / 2
= W
Control Ward

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Industrial Instruments 2
7: Final Control
Signal Conversions
Pneumatic Signals
Pressure signal travels down the pipe at a speed in the range of the speed of sound.

21. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Pneumatic Signals
Pressure signal travels down the pipe at a speed in the range of the speed of sound.
Amplifier (booster or relay)

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Industrial Instruments 2
7: Final Control
Signal Conversions
Pneumatic Signals
Pressure signal travels down the pipe at a speed in the range of the speed of sound.
Amplifier (booster or relay)
Nozzle/Flapper system

23. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Signal Conversions
Pneumatic Signals
Pressure signal travels down the pipe at a speed in the range of the speed of sound.
Amplifier (booster or relay)
Nozzle/Flapper system
Current-to-Pressure converters

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Industrial Instruments 2
7: Final Control
Industrial Electronics
Silicon-Controlled Rectifier (SCR)
Maximum forward current
Peak reverse voltage
Trigger voltage
Trigger current
Holding current

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7: Final Control
Industrial Electronics
SCR Operation:
Half-wave

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Industrial Instruments 2
7: Final Control
Industrial Electronics
SCR Operation:
Full-wave

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Industrial Instruments 2
7: Final Control
Industrial Electronics
SCR Operation: Full-wave (with digital control)

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7: Final Control
Industrial Electronics
SCR Example
An SCR with a 4.0–V trigger is used as a light–dimmer control. What resistance, R, should be used to provide approximately 10% to 90% ON time?

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Industrial Instruments 2
7: Final Control
Industrial Electronics
SCR Example

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Industrial Instruments 2
7: Final Control
Industrial Electronics
SCR Example
VC(t) = VO(1 – e-t/RC)
4.0 = 10 (1 – e-t/RC)
t = RC
T half a cycle = 10 ms
10%  1 ms
90%  9 ms
With C = 0.12 μF
Rmin = 16.3 KΩ
Rmax = 147 KΩ

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Industrial Instruments 2
7: Final Control
Industrial Electronics
TRIAC
DIAC

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Industrial Instruments 2
7: Final Control
Industrial Electronics
TRIAC

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Industrial Instruments 2
7: Final Control
Industrial Electronics
TRIAC Example
An DIAC with a 28–V breakdown voltage is used in the light–dimmer control. What resistance, R, should be used to provide approximately 10% to 90% ON time?

34. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Industrial Electronics
TRIAC Example
When does VAC reach 28 Volts so that it becomes possible to trigger the TRIAC?
28 = 310 sin(314 t)
t = ms
≈ 2.9% of the period
And for 40 Volts:
40 = 310 sin(314 t)
t = ms
≈ 4.1% of the period

35. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Industrial Electronics
TRIAC Example
28 = 40 [ 1 – e – t / RC ]
t = 1.2 RC
If t = 1 ms: Rmin = KΩ
If t = 9 ms: Rmax = 62.5 KΩ

36. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Actuators
Electrical Actuators
Solenoid

37. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Actuators
Electrical Actuators
Solenoid
DC Motor
AC Motor

38. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Actuators
Electrical Actuators
Solenoid
DC Motor
AC Motor
Stepping Motor

39. 3442 - Industrial Instruments 2
Princess Sumaya University
Industrial Instruments 2
7: Final Control
Actuators
Electrical Actuators
Solenoid
DC Motor
AC Motor
Stepping Motor
Pneumatic Actuators

40. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Actuators
Electrical Actuators
Solenoid
DC Motor
AC Motor
Stepping Motor
Pneumatic Actuators
Hydraulic Actuators

41. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Control Elements
Mechanical
Solid-Material Hopper Valves

42. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Control Elements
Mechanical
Paper Thickness

43. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Control Elements
Electrical
Motor Speed Control

44. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Control Elements
Electrical
Temperature Control

45. 3442 - Industrial Instruments 2
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Industrial Instruments 2
7: Final Control
Control Elements
Fluid Valves

46. 3442 - Industrial Instruments 2
Princess Sumaya University
Industrial Instruments 2
7: Final Control
End of Chapter 7