1. Introduction

Force, pressure, and torque are fundamental physical quantities in engineering. Accurate measurement is essential for:

• Design and analysis
• Testing and quality control
• Safety and performance evaluation

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PART A: Measurement of Force

2. Definition of Force

Force is an external action that changes or tends to change the state of a body.$$F = m \times a$$F=m×a

$F = m a$F=ma

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3. Types of Force Measuring Instruments

3.1 Mechanical Force Measuring Devices (Spring Balance)

Principle

Based on Hooke’s Law:$$F = kx$$F=kx

$F = kx$F=kx

$k$k

$F = -kx$F=−kx

Features

• Simple and inexpensive
• Measures tensile force

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3.2 Load Cells

Description

• Widely used modern force sensors

Types

• Strain gauge load cell
• Hydraulic load cell
• Pneumatic load cell

4

Working

• Force causes deformation
• Converted into electrical signal

Advantages

• High accuracy
• Suitable for dynamic measurements

3.3 Proving Ring

Principle

• Elastic deformation of ring under load

Applications

• Calibration of testing machines

PART B: Measurement of Pressure

4. Definition of Pressure

Pressure is force per unit area:$$P = \frac{F}{A}$$P=AF​

$P = \frac{F}{A}$P=AF​

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5. Types of Pressure Measuring Instruments

5.1 Manometers

Types

• U-tube manometer
• Inclined manometer

4

Working

• Pressure measured by liquid column height

5.2 Bourdon Tube Pressure Gauge

Principle

• Elastic deformation of curved tube

4

Features

• Widely used
• Measures medium to high pressure

5.3 Diaphragm Pressure Gauge

Working

• Thin diaphragm deflects under pressure

4

Applications

• Low-pressure measurement

5.4 Dead Weight Pressure Gauge

Principle

• Balances pressure with known weights

4

Use

• Calibration standard

PART C: Measurement of Torque

6. Definition of Torque

Torque is the turning effect of force:$$T = F \times r$$T=F×r

$T = F r$T=Fr

7. Types of Torque Measuring Instruments

7.1 Mechanical Torque Wrench

Description

• Common tool for tightening bolts

Types

• Beam type
• Click type

7.2 Dynamometers

Purpose

• Measure torque and power of engines

Types

• Absorption dynamometer
• Transmission dynamometer

4

7.3 Strain Gauge Torque Meter

Working

• Shaft deformation measured using strain gauges

4

Advantages

• High accuracy
• Real-time measurement

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8. Comparison of Instruments

Quantity	Instrument	Accuracy	Application
Force	Load cell	High	Industrial weighing
Pressure	Bourdon gauge	Medium	General use
Torque	Torque wrench	Medium	Assembly work
Torque	Dynamometer	High	Engine testing

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9. Applications

• Mechanical testing
• Hydraulic systems
• Automotive industry
• Aerospace engineering
• Industrial automation

10. Sources of Error

• Calibration errors
• Temperature variation
• Mechanical wear
• Misalignment
• Electrical noise (in sensors)

11. Advantages of Modern Instruments

• High precision
• Digital output
• Automation compatibility
• Real-time monitoring

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