Speed and Vibration Measurements in Mechanical Engineering

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Questions and Answers

What is the primary function of the core in an inductive displacement sensor?

To change the inductive coupling between the primary and secondary coils based on its displacement (correct)

To provide a stable AC power source to the primary coil

To increase the inductive coupling between the primary and secondary coils

To decrease the inductive coupling between the primary and secondary coils

What is the main advantage of using an inductive displacement sensor over a capacitive pick-up?

More suitable for large displacement measurements

Less sensitive to environmental changes (correct)

Higher accuracy and sensitivity

Require less precise alignment

In a Light Dependent Resistor (LDR) sensor, what is the effect of increasing the light intensity on the LDR?

The LDR's resistance remains constant

The LDR's resistance decreases (correct)

The LDR's resistance increases

The LDR's voltage output increases

What is the main application of capacitive pick-ups?

Micro-electromechanical systems (MEMS) and precision positioning Signup and view all the answers

What is the principle of operation of an inductive displacement sensor?

Measuring changes in inductance Signup and view all the answers

What is the main disadvantage of using a Light Dependent Resistor (LDR) sensor?

Sensitive to ambient light variations Signup and view all the answers

What is the function of the dielectric medium in a capacitive pick-up?

To act as a non-conductive material between the plates Signup and view all the answers

What is the main advantage of using a capacitive pick-up over an inductive displacement sensor?

Higher sensitivity and resolution Signup and view all the answers

What is the principle of operation of a Light Dependent Resistor (LDR) sensor?

Measuring changes in light intensity and corresponding changes in resistance Signup and view all the answers

What is the main application of inductive displacement sensors?

Precision measurement in laboratory and industrial settings Signup and view all the answers

What is the primary function of a stroboscope in rotational speed measurement?

To use a flashing light to make a rotating object appear stationary Signup and view all the answers

Which type of accelerometer is limited by a frequency range and may be affected by temperature changes?

Seismic accelerometer Signup and view all the answers

What is the name of the device that converts rotational speed to a DC voltage?

DC Tachometer Generator Signup and view all the answers

What type of tachometer uses centrifugal force to measure rotational speed?

Centrifugal Tachometer Signup and view all the answers

What is the primary application of a digital tachometer?

Modern machinery and automotive diagnostics Signup and view all the answers

What is the principle of operation of a Vibrating Reed Tachometer?

Uses the resonance frequency of vibrating reeds to measure rotational speed Signup and view all the answers

What is the principle of operation of a strain gauge accelerometer?

Measuring vibration by detecting the strain in a material caused by acceleration forces Signup and view all the answers

What is the purpose of a spring in a Centrifugal Tachometer?

To oppose the centrifugal force and provide a calibrated scale Signup and view all the answers

What is the primary advantage of a mechanical type tachometer?

Simple and robust construction Signup and view all the answers

What type of tachometer is commonly used in older machinery?

Centrifugal Tachometer Signup and view all the answers

What is the primary application of a seismic accelerometer?

Structural health monitoring and earthquake detection Signup and view all the answers

What type of measurement does a stroboscope make?

Speed measurement Signup and view all the answers

What is the principle of operation of a Chronometric Tachometer?

Measures speed based on the time interval between successive pulses Signup and view all the answers

What is the primary component of a DC Tachometer Generator?

Permanent magnet Signup and view all the answers

What is the primary purpose of a Wheatstone Bridge Circuit in the context of acceleration measurement?

To convert strain gauge resistance changes into an electrical signal Signup and view all the answers

What is the main advantage of Piezoelectric Accelerometers over Strain Gauge Accelerometers?

Wide frequency range and high sensitivity Signup and view all the answers

What is the primary principle of operation of an AC Tachometer Generator?

Converting rotational speed to an AC voltage Signup and view all the answers

What is the application of a Vibrating Reed Tachometer?

Measuring the speed of motors and engines Signup and view all the answers

What type of measurement does a seismic accelerometer make?

Vibration measurement Signup and view all the answers

What is the primary application of an electrical type tachometer?

Industrial machinery and automation systems Signup and view all the answers

What is the primary function of the seismic mass in a Piezoelectric Accelerometer?

To apply force to the piezoelectric crystal Signup and view all the answers

Which type of accelerometer is most suitable for low-frequency vibrations and structural health monitoring?

Seismic Accelerometer Signup and view all the answers

What is the component of a Centrifugal Tachometer that is attached to a rotating shaft?

Weighted arms Signup and view all the answers

What is the main advantage of Linear Variable Differential Transformers (LVDTs) in displacement measurement?

High accuracy and precision Signup and view all the answers

What is the purpose of a timing mechanism in a Chronometric Tachometer?

To measure the time interval between successive pulses Signup and view all the answers

Which type of displacement measurement is most suitable for robotics and machine tool alignment?

Angular Displacement Measurement Signup and view all the answers

What is the primary function of a charge amplifier in a Piezoelectric Accelerometer?

To convert the electrical charge into a voltage signal Signup and view all the answers

What is the main disadvantage of Strain Gauge Accelerometers?

Limited dynamic range Signup and view all the answers

Which type of sensor is most suitable for measuring small linear displacements?

Dial Indicator Signup and view all the answers

What is the primary principle of Linear Variable Differential Transformers (LVDTs) in displacement measurement?

Measures linear displacement using the variation in inductance Signup and view all the answers

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 methods of speed and vibration measurements in mechanical engineering, including mechanical and electrical tachometers, stroboscopes, seismic accelerometers, and more.