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3442 Industrial Instruments 2 Chapter 11 Digital Controllers

Princess Sumaya Univ. Electronic Engineering Dept. 3442 Industrial Instruments 2 Chapter 11 Digital Controllers. Dr. Bassam Kahhaleh. 11: Digital Controllers. Digital Electronics Methods Simple Alarm Voltage Comparator. Example : Alarm: Digital output: 5 V when liquid level > 4.2 m

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3442 Industrial Instruments 2 Chapter 11 Digital Controllers

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  1. Princess Sumaya Univ.Electronic Engineering Dept. 3442Industrial Instruments 2Chapter 11DigitalControllers Dr. Bassam Kahhaleh

  2. 3442 - Industrial Instruments 2 11: Digital Controllers Digital Electronics Methods • Simple Alarm • Voltage Comparator. Example: Alarm: Digital output: 5 V when liquid level > 4.2 m Level sensor = 0 – 10 V Liquid level = 0 – 5 m VR = 8.4 V

  3. 3442 - Industrial Instruments 2 11: Digital Controllers Digital Electronics Methods • Two-Position Control Example: Temperature Controller: Output: 220 VAC Fan Turn-On: Temp. > 70 °C Turn-Off: Temp. < 40 °C Temp. sensor: 15 mV/ °C VH = 0.015 * 70 = 1.05 V VL = 0.015 * 40 = 0.60 V

  4. 3442 - Industrial Instruments 2 11: Digital Controllers Digital Electronics Methods • Multivariable Alarm Example: Holding Tank Alarm: Alarm when either: • L2 Low and neither FA nor FB High • L1 High and FA or FB High

  5. 3442 - Industrial Instruments 2 11: Digital Controllers Computers in Process Control • Programmable Logic Controllers • Data Logging Example: Monitor 12 Analog loops. Setup MUX = 20 µs. ADC time = 30 µs. Process sample = 100 Instr. Computer Instr. = 4 µs. Calculate Sampling Rate.

  6. 3442 - Industrial Instruments 2 11: Digital Controllers Computers in Process Control • Programmable Logic Controllers • Data Logging Example: Monitor 12 Analog loops. Setup MUX = 20 µs. ADC time = 30 µs. Process sample = 100 Instr. Computer Instr. = 4 µs. Total execution time for one sample: = ( 20 + 30 + 4x100 ) x 12 = 5400 µs 185 samples / sec

  7. 3442 - Industrial Instruments 2 11: Digital Controllers Computers in Process Control • Programmable Logic Controllers • Data Logging • Supervisory Control

  8. 3442 - Industrial Instruments 2 11: Digital Controllers Computers in Process Control • Programmable Logic Controllers • Data Logging • Supervisory Control • Computer-Based Controller • SBC • PLC • PC • Mainframe

  9. 3442 - Industrial Instruments 2 11: Digital Controllers Characteristics of Digital Data • Digitized Value • Sampled Data System fs = 10 fmax

  10. 3442 - Industrial Instruments 2 11: Digital Controllers Controller Software • Software Format • Flowchart • Machine Language • Assembly Language • High-Level Language (HLL)

  11. 3442 - Industrial Instruments 2 11: Digital Controllers Controller Software • Input Data Operation • Data Input (ADC) • Linearization by equation Example: Pressure Sensor: V=K [p]½. Digitized value: DV varies as [p]½. Calculated Pressure: DP = DV x DV x const.

  12. 3442 - Industrial Instruments 2 11: Digital Controllers Controller Software • Input Data Operation • Data Input (ADC) • Linearization by Equation • Linearization by Table Look-up

  13. 3442 - Industrial Instruments 2 11: Digital Controllers Controller Software • Controller Modes • Proportional Mode Example: Kp = 2.4 Input range: 255 Set point = 130 Output range: 0 – 180 Output without error = 45% • Develop control equations • Find output when input = 124 DE = (130 – DV) / 255 P = 0.45 + 2.4 x DE POUT = P x180 DE = (130 – 124) / 255 = 0.024 P = 0.45 + 2.4 x 0.024 = 0.5076 POUT = 0.5076 x 180 = 91.4

  14. 3442 - Industrial Instruments 2 11: Digital Controllers Controller Software • Controller Modes • Proportional Mode • Integral Mode

  15. 3442 - Industrial Instruments 2 11: Digital Controllers Controller Software • Controller Modes • Proportional Mode • Integral Mode • Derivative Mode

  16. 3442 - Industrial Instruments 2 11: Digital Controllers End of Chapter 11

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