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3441 Industrial Instruments 1 Chapter 5 Mechanical Sensors

Princess Sumaya Univ. Electronic Engineering Dept. 3441 Industrial Instruments 1 Chapter 5 Mechanical Sensors. Dr. Bassam Kahhaleh. Mechanical Sensors. Objective Understand how mechanical sensors work and how to interface them. − +. Mechanical Sensors.

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3441 Industrial Instruments 1 Chapter 5 Mechanical Sensors

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  1. Princess Sumaya Univ.Electronic Engineering Dept. 3441Industrial Instruments 1Chapter 5MechanicalSensors Dr. Bassam Kahhaleh

  2. 3441 - Industrial Instruments 1 Mechanical Sensors Objective Understand how mechanical sensors work and how to interface them.

  3. − + 3441 - Industrial Instruments 1 Mechanical Sensors Displacement, Location, or Position Sensors Potentiometric V S R D R 1 R 3 VR V out R 2 R3 loading effect!!

  4. 3441 - Industrial Instruments 1 Mechanical Sensors Displacement, Location, or Position Sensors Capacitive K = the dielectric constant ε0 = permittivity = 8.85 pF/m A = plate common area D = plate separation

  5. 3441 - Industrial Instruments 1 Mechanical Sensors Displacement, Location, or Position Sensors Inductive Permeable core

  6. 3441 - Industrial Instruments 1 Mechanical Sensors Displacement, Location, or Position Sensors Variable Reluctance Linear Variable Differential Transformer (LVDT)

  7. 3441 - Industrial Instruments 1 Mechanical Sensors Displacement, Location, or Position Sensors LVDT

  8. 3441 - Industrial Instruments 1 Mechanical Sensors Displacement, Location, or Position Sensors Level Sensors • Mechanical • Electrical • Ultrasonic • Pressure

  9. A A F F F F l l 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Stress: Forces applied to an object Strain: the result (deformation) of stress • Tensile Stress-Strain • Compressional Stress-Strain F = applied force in N A = cross-sectional area in m2 Δl = change in length in m l = original length in m

  10. F l A F 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors • Shear Stress-Strain Δx F l F

  11. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Stress-Strain Curve Modulus of elasticity (Young’s modulus): Strain Breaks Necking Linear region Stress

  12. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Strain Gauge (SG) Resistance in metals: Constant volume:

  13. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Strain Gauge - Temperature effect Example: R0 = 120 Ω Strain = 1000 μm / m 0 = 0.004 / °C • Strain ΔR = 0.24 Ω • Temp. ΔR = 0.48 Ω / °C

  14. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Metal Strain Gauges (SGs) Gauge Factor: Typically, GF ~ 2 Special alloys and carbon: GF = 10

  15. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Construction

  16. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Signal Conditioning R 1 R 2 D VS a b R D R A

  17. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Two-arm Bridge D 1 D 2 D VS a b A 1 A 2

  18. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Semiconductor Strain Gauges (SGs) Typically, GF: −50 ~ −200

  19. 3441 - Industrial Instruments 1 Mechanical Sensors Strain Sensors Load Cells

  20. 3441 - Industrial Instruments 1 Mechanical Sensors Motion Sensors Types of Motion • Rectilinear • Angular • Vibration • Shock

  21. 3441 - Industrial Instruments 1 Mechanical Sensors Motion Sensors Accelerometer Spring-Mass System k = spring constant in N/m There is a natural frequency at which the system oscillates without acceleration. Use it with frequency < 1 / (2.5 fN)

  22. 3441 - Industrial Instruments 1 Mechanical Sensors Motion Sensors Types of Accelerometers • Potentiometric • LVDT • Variable Reluctance (small magnet / inductor) • Piezoelectric

  23. C R 2 R V in R 1 V out − + − + 3441 - Industrial Instruments 1 Mechanical Sensors Motion Sensors Steady-State Acceleration Example sensor: 14 mV / g Design: Vout = 0.25 V / (m/s) R = 1 MΩ, C = 1 μF • VIntegral = −1.43 mV / (m/s) • GainInverter = −175

  24. 3441 - Industrial Instruments 1 Mechanical Sensors Pressure Sensors p > 1 atmosphere • Diaphragm

  25. 3441 - Industrial Instruments 1 Mechanical Sensors Pressure Sensors p > 1 atmosphere • Bourdon Tube

  26. 3441 - Industrial Instruments 1 Mechanical Sensors Pressure Sensors p > 1 atmosphere • Solid-State Pressure Sensors

  27. 3441 - Industrial Instruments 1 Mechanical Sensors Pressure Sensors p > 1 atmosphere • Solid-State Pressure Sensors

  28. 3441 - Industrial Instruments 1 Mechanical Sensors Pressure Sensors p < 1 atmosphere In low-pressure environment, the heat loss is proportional to the number of gas molecules per unit volume. • Pirani Gauge Measure filament resistance (RTD) • Thermocouple • Ionization Gauge

  29. 3441 - Industrial Instruments 1 Mechanical Sensors Flow Sensors Solid-Flow Measurement Where: Q = flow (kg /min) W = weight of material on section of length L R = conveyor speed (m/min) L = length of weighing platform (m)

  30. 3441 - Industrial Instruments 1 Mechanical Sensors Flow Sensors Liquid-Flow Restriction Type Where: Q = Volume flow rate K = constant (for the pipe & liquid type) Δp = drop in pressure across the restriction

  31. 3441 - Industrial Instruments 1 Mechanical Sensors Flow Sensors Liquid-Flow Obstruction Type

  32. 3441 - Industrial Instruments 1 Mechanical Sensors Flow Sensors Liquid-Flow Magnetic Type Conducting liquids

  33. 3441 - Industrial Instruments 1 Mechanical Sensors End of Chapter 5

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