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

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Presentation on theme: "3442 Industrial Instruments 2 Chapter 7 Final Control Dr. Bassam Kahhaleh Princess Sumaya Univ. Electronic Engineering Dept."— Presentation transcript:

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

2 Princess Sumaya University Industrial Instruments 22 / 46 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.

3 Princess Sumaya University Industrial Instruments 23 / 46 7: Final Control Operation  Block Diagram Signal Conversions Actuator Final Control Element Process Control Signal

4 Princess Sumaya University Industrial Instruments 24 / 46 7: Final Control Operation  Block Diagram Signal Conversions Actuator Final Control Element Process 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.

5 Princess Sumaya University Industrial Instruments 25 / 46 7: Final Control Operation  Block Diagram Signal Conversions Actuator Final Control Element Process Control Signal The actuator is a translation of the (converted) control signal into action on the control element.

6 Princess Sumaya University Industrial Instruments 26 / 46 7: Final Control Operation  Block Diagram Signal Conversions Actuator Final Control Element Process Control Signal The control element is operated (run) by the actuator.

7 Princess Sumaya University Industrial Instruments 27 / 46 7: Final Control Operation  Block Diagram Signal Conversions Actuator Final Control Element Process Control Signal The process is operation (objective) under control.

8 Princess Sumaya University Industrial Instruments 28 / 46 7: Final Control Operation Example: Baking of Crackers

9 Princess Sumaya University Industrial Instruments 29 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Relays Relays MechanicalMechanical Solid-StateSolid-State Amplifiers Amplifiers TransistorTransistor Op-ampOp-amp

10 Princess Sumaya University Industrial Instruments 210 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Relays Relays MechanicalMechanical

11 Princess Sumaya University Industrial Instruments 211 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Relays Relays MechanicalMechanical

12 Princess Sumaya University Industrial Instruments 212 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Relays Relays MechanicalMechanical

13 Princess Sumaya University Industrial Instruments 213 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Op-amp Op-amp Example : Convert a “4 – 20” mA control signal to a “5 – 10” V signal. Solution : V in = R in * I in V out = K V in + V B 4 20 I (mA) V (Volts) 5 10

14 Princess Sumaya University Industrial Instruments 214 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Op-amp Op-amp Solution : V in = R in * I in Let R in = 100 Ω Vin (V) Vout (V) 5 10

15 Princess Sumaya University Industrial Instruments 215 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Op-amp Op-amp Solution : V out = K V in + V B 5 = K * V B 10 = K * 2 + V B K = V B = 3.75 V out = V in V out = (V in + 1.2) Vin (V) Vout (V) 5 10

16 Princess Sumaya University Industrial Instruments 216 / 46 7: Final Control Signal Conversions  Analog Electrical Signals Op-amp Op-amp Solution : V out = (V in + 1.2)

17 Princess Sumaya University Industrial Instruments 217 / 46 7: Final Control Signal Conversions  Digital Electrical Signals Op-amp Op-amp DAC DAC Direct Action 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.

18 Princess Sumaya University Industrial Instruments 218 / 46 7: Final Control Signal Conversions  Digital Electrical Signals DAC DAC Solution : DAC 10–V reference  2 4 = 16 Therefore: 1111  (15/16) * 10 = V  0 V Amplifier gain = 24 / = 2.56 Incremental step = [(1/16) * 10 ] * 2.56 = 1.6 V ΔV = (1/16) * 10 V

19 Princess Sumaya University Industrial Instruments 219 / 46 7: Final Control Signal Conversions  Digital Electrical Signals DAC DAC Solution : ΔP (from 0000 to 0001) = (1.6 V) 2 / 2 Ω = (1.6 V) 2 / 2 Ω = 1.28 W = 1.28 W ΔP (from 1110 to 1111) = (24) 2 – (22.4) 2 / 2 = (24) 2 – (22.4) 2 / 2 = W = W Power (W) Control Ward

20 Princess Sumaya University Industrial Instruments 220 / 46 7: Final Control Signal Conversions  Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound. Pressure signal travels down the pipe at a speed in the range of the speed of sound.

21 Princess Sumaya University Industrial Instruments 221 / 46 7: Final Control Signal Conversions  Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound. Pressure signal travels down the pipe at a speed in the range of the speed of sound. Amplifier (booster or relay) Amplifier (booster or relay)

22 Princess Sumaya University Industrial Instruments 222 / 46 7: Final Control Signal Conversions  Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound. Pressure signal travels down the pipe at a speed in the range of the speed of sound. Amplifier (booster or relay) Amplifier (booster or relay) Nozzle/Flapper system Nozzle/Flapper system

23 Princess Sumaya University Industrial Instruments 223 / 46 7: Final Control Signal Conversions  Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound. Pressure signal travels down the pipe at a speed in the range of the speed of sound. Amplifier (booster or relay) Amplifier (booster or relay) Nozzle/Flapper system Nozzle/Flapper system Current-to-Pressure converters Current-to-Pressure converters

24 Princess Sumaya University Industrial Instruments 224 / 46 7: Final Control Industrial Electronics  Silicon-Controlled Rectifier (SCR) Maximum forward current Maximum forward current Peak reverse voltage Peak reverse voltage Trigger voltage Trigger voltage Trigger current Trigger current Holding current Holding current

25 Princess Sumaya University Industrial Instruments 225 / 46 7: Final Control Industrial Electronics SCR Operation: SCR Operation: Half-wave

26 Princess Sumaya University Industrial Instruments 226 / 46 7: Final Control Industrial Electronics SCR Operation: SCR Operation: Full-wave

27 Princess Sumaya University Industrial Instruments 227 / 46 7: Final Control Industrial Electronics SCR Operation: Full-wave (with digital control) SCR Operation: Full-wave (with digital control)

28 Princess Sumaya University Industrial Instruments 228 / 46 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?

29 Princess Sumaya University Industrial Instruments 229 / 46 7: Final Control Industrial Electronics SCR Example

30 Princess Sumaya University Industrial Instruments 230 / 46 7: Final Control Industrial Electronics SCR Example V C (t) = V O (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 R min = 16.3 KΩ R max = 147 KΩ

31 Princess Sumaya University Industrial Instruments 231 / 46 7: Final Control Industrial Electronics  TRIAC  DIAC

32 Princess Sumaya University Industrial Instruments 232 / 46 7: Final Control Industrial Electronics  TRIAC

33 Princess Sumaya University Industrial Instruments 233 / 46 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 Princess Sumaya University Industrial Instruments 234 / 46 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 Princess Sumaya University Industrial Instruments 235 / 46 7: Final Control Industrial Electronics TRIAC Example 28 = 40 [ 1 – e – t / RC ] t = 1.2 RC If t = 1 ms: R min = 6.9 KΩ If t = 9 ms: R max = 62.5 KΩ

36 Princess Sumaya University Industrial Instruments 236 / 46 7: Final Control Actuators  Electrical Actuators Solenoid Solenoid

37 Princess Sumaya University Industrial Instruments 237 / 46 7: Final Control Actuators  Electrical Actuators Solenoid Solenoid DC Motor DC Motor AC Motor AC Motor

38 Princess Sumaya University Industrial Instruments 238 / 46 7: Final Control Actuators  Electrical Actuators Solenoid Solenoid DC Motor DC Motor AC Motor AC Motor Stepping Motor Stepping Motor

39 Princess Sumaya University Industrial Instruments 239 / 46 7: Final Control Actuators  Electrical Actuators Solenoid Solenoid DC Motor DC Motor AC Motor AC Motor Stepping Motor Stepping Motor  Pneumatic Actuators

40 Princess Sumaya University Industrial Instruments 240 / 46 7: Final Control Actuators  Electrical Actuators Solenoid Solenoid DC Motor DC Motor AC Motor AC Motor Stepping Motor Stepping Motor  Pneumatic Actuators  Hydraulic Actuators

41 Princess Sumaya University Industrial Instruments 241 / 46 7: Final Control Control Elements  Mechanical Solid-Material Hopper Valves Solid-Material Hopper Valves

42 Princess Sumaya University Industrial Instruments 242 / 46 7: Final Control Control Elements  Mechanical Paper Thickness Paper Thickness

43 Princess Sumaya University Industrial Instruments 243 / 46 7: Final Control Control Elements  Electrical Motor Speed Control Motor Speed Control

44 Princess Sumaya University Industrial Instruments 244 / 46 7: Final Control Control Elements  Electrical Temperature Control Temperature Control

45 Princess Sumaya University Industrial Instruments 245 / 46 7: Final Control Control Elements  Fluid Valves

46 Princess Sumaya University Industrial Instruments 246 / 46 7: Final Control End of Chapter 7


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