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

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Presentation on theme: "3441 Industrial Instruments 1 Chapter 5 Mechanical Sensors Dr. Bassam Kahhaleh Princess Sumaya Univ. Electronic Engineering Dept."— Presentation transcript:

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

2 Princess Sumaya University Industrial Instruments 12 / 33 Mechanical Sensors Objective Understand how mechanical sensors work and how to interface them.

3 Princess Sumaya University Industrial Instruments 13 / 33 Mechanical Sensors Displacement, Location, or Position Sensors Potentiometric V out R 3 −+−+ R D R 1 R 2 V S VRVR R 3 loading effect!!

4 Princess Sumaya University Industrial Instruments 14 / 33 Mechanical Sensors Displacement, Location, or Position Sensors Capacitive K = the dielectric constant ε 0 = permittivity = 8.85 pF/m A = plate common area D = plate separation

5 Princess Sumaya University Industrial Instruments 15 / 33 Mechanical Sensors Displacement, Location, or Position Sensors Inductive Permeable core

6 Princess Sumaya University Industrial Instruments 16 / 33 Mechanical Sensors Displacement, Location, or Position Sensors Variable Reluctance Linear Variable Differential Transformer (LVDT)

7 Princess Sumaya University Industrial Instruments 17 / 33 Mechanical Sensors Displacement, Location, or Position Sensors LVDT

8 Princess Sumaya University Industrial Instruments 18 / 33 Mechanical Sensors Displacement, Location, or Position Sensors Level Sensors  Mechanical  Electrical  Ultrasonic  Pressure

9 Princess Sumaya University Industrial Instruments 19 / 33 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 m 2 Δl = change in length in m l = original length in m A FF l A FF l

10 Princess Sumaya University Industrial Instruments 110 / 33 Mechanical Sensors Strain Sensors  Shear Stress-Strain F F l A l ΔxΔx F F

11 Princess Sumaya University Industrial Instruments 111 / 33 Mechanical Sensors Strain Sensors Stress-Strain Curve Modulus of elasticity (Young’s modulus): Strain Stress Linear region Necking Breaks

12 Princess Sumaya University Industrial Instruments 112 / 33 Mechanical Sensors Strain Sensors Strain Gauge (SG) Resistance in metals: Constant volume:

13 Princess Sumaya University Industrial Instruments 113 / 33 Mechanical Sensors Strain Sensors Strain Gauge - Temperature effect Example: R 0 = 120 Ω Strain = 1000 μm / m  0 = / °C   Strain ΔR = 0.24 Ω   Temp. ΔR = 0.48 Ω / °C

14 Princess Sumaya University Industrial Instruments 114 / 33 Mechanical Sensors Strain Sensors Metal Strain Gauges (SGs) : Gauge Factor: Typically, GF ~ 2 Special alloys and carbon: GF = 10

15 Princess Sumaya University Industrial Instruments 115 / 33 Mechanical Sensors Strain Sensors Construction

16 Princess Sumaya University Industrial Instruments 116 / 33 Mechanical Sensors Strain Sensors Signal Conditioning R 1 R 2 R D VSVS D R A ab

17 Princess Sumaya University Industrial Instruments 117 / 33 Mechanical Sensors Strain Sensors Two-arm Bridge D 1 D 2 A 1 VSVS D A 2 ab

18 Princess Sumaya University Industrial Instruments 118 / 33 Mechanical Sensors Strain Sensors Semiconductor Strain Gauges (SGs) Typically, GF: −50 ~ −200

19 Princess Sumaya University Industrial Instruments 119 / 33 Mechanical Sensors Strain Sensors Load Cells

20 Princess Sumaya University Industrial Instruments 120 / 33 Mechanical Sensors Motion Sensors Types of Motion  Rectilinear  Angular  Vibration  Shock

21 Princess Sumaya University Industrial Instruments 121 / 33 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 f N )

22 Princess Sumaya University Industrial Instruments 122 / 33 Mechanical Sensors Motion Sensors Types of Accelerometers  Potentiometric  LVDT  Variable Reluctance (small magnet / inductor)  Piezoelectric

23 Princess Sumaya University Industrial Instruments 123 / 33 Mechanical Sensors Motion Sensors Steady-State Acceleration Example sensor: 14 mV / g Design: V out = 0.25 V / (m/s) R = 1 MΩ, C = 1 μF  V Integral = −1.43 mV / (m/s)  Gain Inverter = −175 R V in −+−+ C V out R 1 −+−+ R 2

24 Princess Sumaya University Industrial Instruments 124 / 33 Mechanical Sensors Pressure Sensors p > 1 atmosphere  Diaphragm

25 Princess Sumaya University Industrial Instruments 125 / 33 Mechanical Sensors Pressure Sensors p > 1 atmosphere  Bourdon Tube

26 Princess Sumaya University Industrial Instruments 126 / 33 Mechanical Sensors Pressure Sensors p > 1 atmosphere  Solid-State Pressure Sensors

27 Princess Sumaya University Industrial Instruments 127 / 33 Mechanical Sensors Pressure Sensors p > 1 atmosphere  Solid-State Pressure Sensors

28 Princess Sumaya University Industrial Instruments 128 / 33 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 Princess Sumaya University Industrial Instruments 129 / 33 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 Princess Sumaya University Industrial Instruments 130 / 33 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 Princess Sumaya University Industrial Instruments 131 / 33 Mechanical Sensors Flow Sensors Liquid-Flow Obstruction Type

32 Princess Sumaya University Industrial Instruments 132 / 33 Mechanical Sensors Flow Sensors Liquid-Flow Magnetic Type Conducting liquids liquids

33 Princess Sumaya University Industrial Instruments 133 / 33 End of Chapter 5 Mechanical Sensors


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