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Questions and Answers
What is the primary function of a tachometer?
Which type of tachometer is suitable for industrial machinery and automation systems?
What is the principle of operation of a stroboscope?
What is the main advantage of using seismic accelerometers?
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What is the purpose of a strain gauge in a strain gauge accelerometer?
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Which type of accelerometer is commonly used in structural health monitoring?
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What is the primary application of a digital tachometer?
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What is the main disadvantage of seismic accelerometers?
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What is the purpose of a commutator in a DC tachometer generator?
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What is the primary use of vibration measurement in mechanical engineering?
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What is the main purpose of speed measurement in mechanical engineering applications?
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Which type of tachometer uses centrifugal force to measure rotational speed?
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What is the principle of operation of a chronometric tachometer?
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What is the application of a vibrating reed tachometer?
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Which of the following is not a type of tachometer?
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What is the component of a centrifugal tachometer that moves outward against the spring force?
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What is the principle of operation of a vibrating reed tachometer?
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What is measured by a chronometric tachometer?
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What is the application of a centrifugal tachometer?
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Which type of measurement is done using seismic, strain gauge, and piezoelectric accelerometers?
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What is the primary function of the core in a Linear Variable Differential Transformer (LVDT)?
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What is the main advantage of using an LVDT over other displacement measurement methods?
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What is the operating principle of a Light Dependent Resistor (LDR)?
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What is the main disadvantage of using a Capacitive Pick-up?
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What is the primary application of Inductive Pick-ups?
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What is the main advantage of using an LVDT over an LDR?
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What is the operating principle of a Capacitive Pick-up?
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What is the main disadvantage of using an LVDT?
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What is the primary application of an LDR?
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What is the main advantage of using a Capacitive Pick-up over an Inductive Pick-up?
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What is the primary function of a Wheatstone Bridge Circuit in an accelerometer?
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What is the main advantage of piezoelectric accelerometers?
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What is the primary application of seismic accelerometers?
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What is the principle of linear variable differential transformers (LVDTs)?
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What is the main advantage of strain gauge accelerometers?
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What is the primary application of linear displacement resistors (LDRs)?
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What is the principle of angular displacement measurement?
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What is the primary application of rotary encoders?
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What is the primary disadvantage of piezoelectric accelerometers?
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What is the primary application of inductive pick-ups?
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Study Notes
Speed Measurements in Mechanical Engineering
- Speed measurement is essential in various mechanical engineering applications to monitor and control the rotational speed of machines, engines, and other mechanical systems.
- Different types of tachometers (mechanical and electrical) and stroboscopes are used for speed measurement.
Mechanical Type Tachometers
- Centrifugal Tachometer: uses centrifugal force to measure rotational speed; components: weighted arms, spring, and scale; applications: older machinery, educational demonstrations.
- Chronometric Tachometer: measures speed based on time interval between successive pulses; components: rotating element, timing mechanism, and dial; applications: vintage vehicles, historical equipment.
- Vibrating Reed Tachometer: uses resonance frequency of vibrating reeds to measure rotational speed; components: set of reeds, each tuned to resonate at a specific frequency; applications: portable speed measurement, industrial equipment.
Electrical Type Tachometers
- DC Tachometer Generator: converts rotational speed to a DC voltage; components: permanent magnet, armature winding, commutator, brushes; applications: industrial machinery, automation systems.
- AC Tachometer Generator: converts rotational speed to an AC voltage; components: rotor, stator windings; applications: motors, generators, speed control systems.
- Digital Tachometer: uses electronic sensors to measure rotational speed and display it digitally; components: optical or magnetic sensors, microprocessor, digital display; applications: modern machinery, automotive diagnostics, laboratory equipment.
Stroboscope
- Uses a flashing light to make a rotating or vibrating object appear stationary, allowing for measurement of its speed; components: light source, control unit, and viewing area; applications: rotational speed measurement, vibration analysis, machinery maintenance.
Vibration Measurements in Mechanical Engineering
- Vibration measurement is crucial in various mechanical engineering applications, including machinery health monitoring, structural analysis, and quality control.
- Different types of accelerometers (seismic, strain gauge, and piezoelectric) are used to measure vibrations.
Seismic Accelerometers
- Measure vibration by detecting the relative motion between a mass and its housing; components: seismic mass, spring/damper system, and transducer; advantages: simple construction, robust, and reliable; disadvantages: limited frequency range, affected by temperature changes; applications: structural health monitoring, earthquake detection, low-frequency vibration measurement.
Strain Gauge Accelerometers
- Measure vibration by detecting the strain in a material caused by acceleration forces; components: strain gauges, flexible element, and Wheatstone bridge circuit; advantages: high sensitivity, suitable for low-frequency vibrations; disadvantages: limited dynamic range, sensitive to temperature variations; applications: structural testing, machinery health monitoring, aerospace applications.
Piezoelectric Accelerometers
- Measure vibration by converting mechanical stress into an electrical charge using piezoelectric materials; components: piezoelectric crystal, seismic mass, and charge amplifier; advantages: wide frequency range, high sensitivity and stability, good temperature stability; disadvantages: requires charge amplifier or signal conditioner, may be affected by base strain and thermal transients; applications: machinery condition monitoring, modal analysis, vibration testing in automotive and aerospace industries.
Displacement Measurements in Mechanical Engineering
- Displacement measurements are essential in various mechanical engineering applications to monitor and control the position, movement, and alignment of components.
- These measurements can be linear or angular, and several types of sensors are used to measure displacement accurately.
Linear Displacement Measurements
- Rulers and Vernier Calipers: simple mechanical devices for direct measurement; applications: precision machining, material testing, structural deformation monitoring.
- Dial Indicators: mechanical devices for precise measurement of small linear displacements; applications: precision machining, material testing.
- Linear Variable Differential Transformers (LVDTs): sensors that provide accurate and continuous measurement; applications: precision measurement in laboratory and industrial settings, aerospace and automotive testing, material testing machines.
Angular Displacement Measurements
- Protractors and Angle Gauges: simple mechanical devices for direct measurement; applications: robotics, machine tool alignment, automotive steering systems.
- Rotary Encoders: electronic devices for precise measurement; applications: robotics, machine tool alignment.
- Inductive and Capacitive Pick-ups: sensors that provide accurate and continuous measurement; applications: robotics, machine tool alignment, automotive steering systems.
Linear Variable Differential Transformer (LVDT)
- Measures linear displacement using the variation in inductance; components: primary coil, secondary coils, and core; advantages: high accuracy and sensitivity, no physical contact between the core and coils, long life and reliability; disadvantages: sensitive to temperature variations, requires an AC power source; applications: precision measurement in laboratory and industrial settings, aerospace and automotive testing, material testing machines.
Light Dependent Resistor (LDR)
- Measures displacement based on changes in light intensity and corresponding changes in resistance; components: LDR sensor, light source, and moving object; advantages: simple and inexpensive, non-contact measurement; disadvantages: sensitive to ambient light variations, limited accuracy and resolution; applications: position sensing in robotics, light-sensitive switches, basic displacement measurements.
Capacitive Pick-ups
- Measure displacement by detecting changes in capacitance between two conductive plates; components: conductive plates, dielectric medium, and electronics; advantages: high sensitivity and resolution, suitable for small displacement measurements, non-contact measurement; disadvantages: sensitive to environmental changes (e.g., humidity, temperature), requires precise alignment; applications: micro-electromechanical systems (MEMS), precision positioning in semiconductor manufacturing, gap measurement in machinery.
Inductive Pick-ups
- Measure displacement by detecting changes in inductance; components: coil and core; applications: precision measurement, gap measurement in machinery.
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Description
This quiz covers various measurement techniques in mechanical engineering, including speed, vibration, and displacement measurements using different types of tachometers, accelerometers, and pick ups.
