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3441 Industrial Instruments 1 Chapter 3 Digital Signal Conditioning Dr. Bassam Kahhaleh Princess Sumaya Univ. Electronic Engineering Dept.

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Presentation on theme: "3441 Industrial Instruments 1 Chapter 3 Digital Signal Conditioning Dr. Bassam Kahhaleh Princess Sumaya Univ. Electronic Engineering Dept."— Presentation transcript:

1 3441 Industrial Instruments 1 Chapter 3 Digital Signal Conditioning Dr. Bassam Kahhaleh Princess Sumaya Univ. Electronic Engineering Dept.

2 Princess Sumaya University Industrial Instruments 12 / 22 Digital Signal Conditioning Objective Introduce the basic technique of digital signal conditioning, especially interfacing, in process control.

3 Princess Sumaya University Industrial Instruments 13 / 22 Digital Signal Conditioning Digital Signals Level Pressure Temperature

4 Princess Sumaya University Industrial Instruments 14 / 22 Digital Signal Conditioning Digital Signals TTL Output Totem-pole Totem-pole Tri-state Tri-state Open-collector Open-collector I H = 0.04 mA I L = 1.6 mA I H = 0.4 mA I L = 16 mA

5 Princess Sumaya University Industrial Instruments 15 / 22 Digital Signal Conditioning TTL Interfacing  Never leave inputs unconnected  Never short-circuit outputs to ground or Vcc  Never short-circuit outputs together unless they are tri-state or open-collector outputs  Never use pull-down resistors  Be careful when using different power supplies (V CC1 = +5, V CC2 = +12).

6 Princess Sumaya University Industrial Instruments 16 / 22 Digital Signal Conditioning TTL Interfacing IRIR What is the minimum resistance value? When the tri-state output is floating: V should be max 0.8, I R = 1.6 mA  R = 0.8 / 1.6 = 0.5 KΩ V Now what happens when the tri-state output goes high? V should be min 2.4 V, therefore I R = 2.4 / 0.5 K = 4.8 mA !!

7 Princess Sumaya University Industrial Instruments 17 / 22 Digital Signal Conditioning TTL Interfacing IRIR Typically, R = 10 KΩ  I R max = (5 – 0.2) / 10 = 0.48 mA V +V CC Now what is the value of V when the tri-state outputs goes floating? I R = 0.04 mA  V = 5 – 0.04 x 10 = 4.6 Volts +V CC

8 Princess Sumaya University Industrial Instruments 18 / 22 Digital Signal Conditioning TTL Interfacing IRIR LED: V = 1.5 ~ 1.6 V I = 10 ~ 15 mA +V CC Standard TTL gates should not source such current to a LED, but it can sink it. What is the minimum value of R? V O max = 0.8 V, I R = 15 mA  R = (5 – 1.5 – 0.8) / 15 = 0.18 KΩ Typically, V O max = 0.2 V, I R = 15 mA, R = 220 Ω VoVo R

9 Princess Sumaya University Industrial Instruments 19 / 22 Digital Signal Conditioning TTL Interfacing IRIR +V CC2 V CC2 > V CC1 VoVo R +V CC1

10 Princess Sumaya University Industrial Instruments 110 / 22 Digital Signal Conditioning TTL Interfacing R Relay current = 40 mA β = 100  I B = 0.4 mA R = (2.4 – 0.7) / 0.4 = 4.25 KΩ

11 Princess Sumaya University Industrial Instruments 111 / 22 Digital Signal Conditioning ConvertersComparators Alarm +−+− +−+− V 2.0 V 2.2 mV/°C 0.2 V / kPa T P Comparators’ Power Supply?

12 Princess Sumaya University Industrial Instruments 112 / 22 Digital Signal Conditioning Converters Hysteresis Comparators +−+− R R f V in V ref V out VLVL VOVO 0 VHVH V in

13 Princess Sumaya University Industrial Instruments 113 / 22 Digital Signal Conditioning Converters Digital-to-Analog Converters (DAC) Bipolar DAC Conversion Resolution?

14 Princess Sumaya University Industrial Instruments 114 / 22 Digital Signal Conditioning Converters R-2R ladder DAC V out R VRVR −+−+ R b0b1b2b3b0b1b2b3 RR 2R

15 Princess Sumaya University Industrial Instruments 115 / 22 Digital Signal Conditioning Converters R-2R ladder DAC V out R −+−+ R RR 2R VRVR V TH R TH = R = ½ V R

16 Princess Sumaya University Industrial Instruments 116 / 22 Digital Signal Conditioning Converters R-2R ladder DAC V out R −+−+ R RR 2R ½ V R R V TH R TH = R = ¼ V R

17 Princess Sumaya University Industrial Instruments 117 / 22 Digital Signal Conditioning Converters Analog-to-Digital Converters (ADC) Bipolar ADC Conversion Resolution?

18 Princess Sumaya University Industrial Instruments 118 / 22 Digital Signal Conditioning Converters Parallel Feedback ADC Logic Counting Network DAC Comparator VXVX... b n-1 b n-2 b 1 b 0 SC EOC

19 Princess Sumaya University Industrial Instruments 119 / 22 Digital Signal Conditioning Converters Ramp ADC (Dual-Slope) Digital Counter Logic Control Comparator −VX−VX b n-1 b n-2 b 1 b 0 SC EOC −+−+ +VR+VR R C T1T1 VOVO V1V1 0 t x t VOVO

20 Princess Sumaya University Industrial Instruments 120 / 22 Digital Signal Conditioning Converters Conversion-Time Consequences  C C ViVi t VNVN V N+1

21 Princess Sumaya University Industrial Instruments 121 / 22 Digital Signal Conditioning Converters Sample-and-Hold (S/H) +−+− ADC C V in (t) S/H V c (t)

22 Princess Sumaya University Industrial Instruments 122 / 22 End of Chapter 3 Digital Signal Conditioning


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