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

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

Analog Signal Conditioning Princess Sumaya University 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.

Analog Signal Conditioning Princess Sumaya University 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 & Impedance Matching Loading Vx Rx Vy R L Sensor x

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits Bridge Circuits Wheatstone Bridge R 1 R 2 D V R 3 R 4

Analog Signal Conditioning Princess Sumaya University 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 a b R G R 3 R 4 b

Analog Signal Conditioning Princess Sumaya University 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 a b R G R 3 R 4 b

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits Bridge Circuits AC Bridges Z 2 Z 1  D V Z 3 Z 4

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Passive Circuits RC Filters Low-pass RC Filters R C V in V out Gain 1 ω ω0

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

Analog Signal Conditioning Princess Sumaya University 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?

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 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

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

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Inverting Amplifier R 2 R 1 − + V in V out

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Summing Amplifier R 1 R 3 V 1 − + V 2 R 2 V out

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 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

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Current-to-Voltage Converter R I − + V out R

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Integrator C R − + V in V out

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Differentiator R C − + V in V out

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Power Supply +V CC V CC V in − + V out t V CC −V CC

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Power Supply +V CC V in − + V CC V out t

Analog Signal Conditioning Princess Sumaya University 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 t

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning Operational Amplifiers Power Supply +V CC − + V CC V out V in t

Analog Signal Conditioning Princess Sumaya University 3441 - Industrial Instruments 1 Analog Signal Conditioning End of Chapter 2