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Subject - MEASUREMENTS & METROLOGY ME 4001(Same in MA 4001)
Branch - Mechanical Engineering
Semester - 4th Semester

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3. APPLIED MECHANICAL MEASUREMENTS

Applied Mechanical Measurements refer to the techniques and instruments used to measure various mechanical quantities. These measurements are essential for monitoring the performance, accuracy, and efficiency of machines, systems, and industrial processes.

Mechanical measurements can be classified into different categories based on the quantity being measured, such as speed, displacement, flow, temperature, and other miscellaneous measurements.

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3.1 Speed Measurement

Speed measurement is used to determine the linear or rotational speed of an object, machine, or vehicle. Speed can be classified into:

1. Linear Speed Measurement: Measures the speed of an object moving in a straight line.

2. Angular Speed Measurement: Measures the rotational speed of an object around an axis.

Instruments for Speed Measurement:

1. Tachometer:

   • Used to measure the rotational speed of a shaft or disk in revolutions per minute (RPM).

   • Types of tachometers:

     • Contact Tachometer: Requires physical contact with the rotating surface.

     • Non-Contact Tachometer: Uses laser or optical sensors to measure speed from a distance.

2. Stroboscope:

   • Uses flashing light at adjustable frequencies.

   • When the frequency of the flashing light matches the rotation of an object, the object appears stationary, allowing its speed to be determined.

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3.2 Displacement Measurement

Displacement measurement is used to determine how far an object has moved from its original position.

Instruments for Displacement Measurement:

1. LVDT (Linear Variable Differential Transformer):

   • An electromagnetic sensor that measures linear displacement with high accuracy.

   • Commonly used in industrial and scientific applications.

2. Vernier Scale:

   • A precision instrument used to measure small linear displacements (up to 0.01 mm accuracy).

   • Used in engineering, machining, and laboratory experiments.

3. Dial Gauge:

   • Measures small displacements with high precision.

   • Used to check the accuracy of machine parts.

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3.3 Flow Measurement

Flow measurement determines the quantity of liquid or gas flowing through a pipe or channel.

Instruments for Flow Measurement:

1. Orifice Meter:

   • Uses a small hole (orifice plate) in a pipe to measure fluid flow based on pressure differences.

2. Venturi Meter:

   • Has a constricted section in a pipe to measure the flow rate based on fluid velocity.

   • More accurate than an orifice meter.

3. Rotameter:

   • Consists of a transparent tube with a floating object that rises or falls based on fluid flow.

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3.4 Temperature Measurement

Temperature measurement is used to determine the heat level of a substance, environment, or system.

Instruments for Temperature Measurement:

1. Thermocouple:

   • Measures temperature based on the voltage generated between two dissimilar metals.

   • Can measure high temperatures (up to 1000°C).

2. Thermometer:

   • Commonly used for temperature measurement.

   • Types:

     • Mercury Thermometer

     • Digital Thermometer

3. Pyrometer:

   • Measures very high temperatures (such as in furnaces or metal casting).

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3.5 Miscellaneous Measurements

3.5.1 Humidity Measurement – Hair Hygrometer

• Measures the moisture content (humidity) in the air.

• Uses human or animal hair, which expands or contracts with changes in humidity.

3.5.2 Density Measurement – Hydrometer

• Measures the density of liquids.

• A cylindrical device that floats in the liquid, and its depth of immersion determines the density.

3.5.3 Liquid Level Measurement

1. Sight Glass:

   • A transparent tube attached to a container that shows the liquid level.

2. Float Gauge:

   • Uses a floating object that moves up and down based on the liquid level.

3.5.4 Biomedical Measurement – Sphygmomanometer

• Measures blood pressure.

• Consists of an inflatable cuff, a pressure gauge, and a pump.

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Conclusion:

• Applied mechanical measurements are essential for monitoring and controlling various industrial, scientific, and biomedical processes.

• Different instruments are available for measuring speed, displacement, flow, temperature, and other quantities.

• These measurements ensure accuracy, efficiency, and safety in engineering and medical applications.