3441 Industrial Instruments 1 Chapter 2 Analog Signal Conditioning - PowerPoint PPT Presentation

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3441 Industrial Instruments 1 Chapter 2 Analog Signal Conditioning

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  1. Princess Sumaya Univ.Electronic Engineering Dept. 3441Industrial Instruments 1Chapter 2Analog Signal Conditioning Dr. Bassam Kahhaleh

  2. 3441 - Industrial Instruments 1 Analog Signal Conditioning Objective Introduce the basic technique of signal conditioning in process control.

  3. 3441 - Industrial Instruments 1 Analog Signal Conditioning Definition Signal conditioning refers to operations performed on signals to convert them to a form suitable for interface with other elements in the process-control loop.

  4. Sensor x Rx Vx Vy R L 3441 - Industrial Instruments 1 Analog Signal Conditioning Principles of Analog Signal Conditioning • Signal-Level and Bias Changes • Linearization • Conversions • Current Signal (4 – 20 mA) • Digital Interface • Filtering & ImpedanceMatching • Loading

  5. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Divider Circuits Loading effect of RL RL >> R2 V S R 1 V D R 2 R L


  6. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Divider Circuits Self-heating (R2 is a temperature sensor) Example VS = 5 V R1 = 10 K Ω 4 KΩ ≤ R2 ≤ 12 KΩ  1.43 V ≤ VD ≤ 2.73 V 0.51 mW ≤ PD ≤ 0.62 mW V S R 1 V D R 2

  7. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Bridge Circuits • Wheatstone Bridge R 1 R 2 D V R 3 R 4

  8. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Bridge Circuits • Wheatstone Bridge Galvanometer Detector Galvanometer R Th a R 1 R 2 D VTh V R G a b R 3 R 4 b

  9. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Bridge Circuits • Wheatstone Bridge Bridge Resolution (Ideal & Non ideal Detector) R Th a R 1 R 2 D VTh V R G a b R 3 R 4 b

  10. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Bridge Circuits • Wheatstone Bridge Lead Compensation R 1 R 2 D V a b R 3 R 4 c

  11. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Bridge Circuits • Wheatstone Bridge Current Balance Bridge R 1 R 2 a D b R4 >> R5 (R2+R4) >> R5 V R 4 R 3 I R 5

  12. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Bridge Circuits • Wheatstone Bridge Potential Measurement Using Bridges R 1 R 2 Vc = Vx+ Va a c D b V V x R 3 R 4

  13. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • Bridge Circuits • AC Bridges Z 2 Z 1  D V Z 3 Z 4

  14. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • RC Filters • Low-pass RC Filters R C V out V in Gain 1 ω ω0

  15. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • RC Filters • Low-pass RC Filters Cascaded Stages R 1 R 2 C 2 V out C 1 V in Gain 1 ω ω0 Loading Effect  R2 >> R1, C2 << C1

  16. 3441 - Industrial Instruments 1 Analog Signal Conditioning Example 2.11 A measured signal has a frequency < 1 KHz, but there is unwanted noise at about 1 MHz. Design a low-pass filter that attenuates the noise to 1%. What is the effect on the measurement signal at it max. of 1 KHz?

  17. 3441 - Industrial Instruments 1 Analog Signal Conditioning Example 2.11 Vout / Vin = 0.01 at 1 MHz  fc = 10 KHz Use C = 0.47 μF  R = 33.9 Ω(too small -> too much current) Use C = 0.01 μF  R = 1591 Ω Standard R = 1.5 KΩ  fc = 10610 Hz Vout / Vin = 0.0099995 At 1 KHz: Vout / Vin = 0.996

  18. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • RC Filters • High-pass RC Filters C V in V out R Gain 1 ω ω0

  19. 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits • RC Filters • Band-pass RC Filters C H Gain R L 1 C L V out V in R H ω ω2 ω1 If ω1 << ω2 Then you use the individual equations for the LPF and HPF

  20. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Inverting Amplifier R 2 R 1 V in V out

  21. + − + − 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Non Inverting Amplifier V in V out R 2 R 1 V in V out = V in

  22. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Summing Amplifier R 1 R 3 V 1 V 2 R 2 V out

  23. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Differential Amplifier R 1 R 2 V 2 R 1 V 1 V out R 2

  24. + − + + − 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Differential Instrumentation Amplifier V 2 R 1 R 2 R 3 R G R 2 V out R 1 R 3 V 1

  25. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Voltage-to-Current Converter R 1 R 2 V in R 3 R 5 I L R 4 R L

  26. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Current-to-Voltage Converter R I V out R

  27. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Integrator C R V in V out

  28. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Differentiator R C V in V out

  29. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Power Supply +V CC V CC V in V out 0 t V CC −V CC

  30. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Power Supply +V CC V in V out V CC 0 t

  31. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Power Supply +V CC + − V CC V in ½ V CC V out ½ V CC 0 t

  32. + 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers • Power Supply +V CC V CC V out V in 0 t

  33. 3441 - Industrial Instruments 1 Analog Signal Conditioning End of Chapter 2