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

Princess Sumaya University Industrial Instruments 22 / 16 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 V R = 8.4 V

Princess Sumaya University Industrial Instruments 23 / 16 11: Digital Controllers Digital Electronics Methods  Two-Position Control Example: Temperature Controller: Output: 220 V AC Fan Turn-On: Temp. > 70 °C Turn-Off: Temp. < 40 °C Temp. sensor: 15 mV/ °C V H = * 70 = 1.05 V = 1.05 V V L = * 40 = 0.60 V = 0.60 V

Princess Sumaya University Industrial Instruments 24 / 16 11: Digital Controllers Digital Electronics Methods  Multivariable Alarm Example: Holding Tank Alarm: Alarm when either: L 2 Low and neither FA nor FB High L 1 High and FA or FB High

Princess Sumaya University Industrial Instruments 25 / 16 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.

Princess Sumaya University Industrial Instruments 26 / 16 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: = ( x100 ) x 12 = 5400 µs 185 samples / sec

Princess Sumaya University Industrial Instruments 27 / 16 11: Digital Controllers Computers in Process Control  Programmable Logic Controllers  Data Logging  Supervisory Control

Princess Sumaya University Industrial Instruments 28 / 16 11: Digital Controllers Computers in Process Control  Programmable Logic Controllers  Data Logging  Supervisory Control  Computer-Based Controller Controller SBC SBC PLC PLC PC PC Mainframe Mainframe

Princess Sumaya University Industrial Instruments 29 / 16 11: Digital Controllers Characteristics of Digital Data  Digitized Value  Sampled Data System f s = 10 f max

Princess Sumaya University Industrial Instruments 210 / 16 11: Digital Controllers Controller Software  Software Format Flowchart Flowchart Machine Language Machine Language Assembly Language Assembly Language High-Level Language (HLL) High-Level Language (HLL)

Princess Sumaya University Industrial Instruments 211 / 16 11: Digital Controllers Controller Software  Input Data Operation Data Input (ADC) Data Input (ADC) Linearization by equation 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.

Princess Sumaya University Industrial Instruments 212 / 16 11: Digital Controllers Controller Software  Input Data Operation Data Input (ADC) Data Input (ADC) Linearization by Equation Linearization by Equation Linearization by Table Look-up Linearization by Table Look-up

Princess Sumaya University Industrial Instruments 213 / 16 11: Digital Controllers Controller Software  Controller Modes Proportional Mode Proportional Mode Example: K p = 2.4 Input range: 255 Set point = 130 Output range: 0 – 180 Output without error = 45% a) a)Develop control equations b) b)Find output when input = 124 DE = (130 – DV) / 255 P = x DE POUT = P x 180 DE = (130 – 124) / 255 = P = x = POUT = x 180 = 91.4

Princess Sumaya University Industrial Instruments 214 / 16 11: Digital Controllers Controller Software  Controller Modes Proportional Mode Proportional Mode Integral Mode Integral Mode

Princess Sumaya University Industrial Instruments 215 / 16 11: Digital Controllers Controller Software  Controller Modes Proportional Mode Proportional Mode Integral Mode Integral Mode Derivative Mode Derivative Mode

Princess Sumaya University Industrial Instruments 216 / 16 11: Digital Controllers End of Chapter 11