ME3592 -

METROLOGY AND
MEASUREMENTS
PREPARED BY
Dr. J. PRADEEP KUMAR – AP
DEPARTMENT OF MECHANICAL ENGINEERING
KINGS ENGINEERING COLLEGE
CHENNAI
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COURSE OUTCOME
1. To learn basic concepts of the metrology and importance of
measurements

2. To teach measurement of linear and angular dimensions assembly and

transmission elements

3. To study the tolerance analysis in manufacturing

4. To develop the fundamentals of GD & T and surface metrology

5. To provide the knowledge of the advanced measurements for quality

control in manufacturing industries
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UNITS
UNIT 1 BASICS OF METROLOGY
• Measurement – Need, Process, Role in quality control; Factors affecting measurement -
SWIPE; Errors in Measurements – Types – Control – Measurement uncertainty – Types,
Estimation, Problems on Estimation of Uncertainty, Statistical analysis of measurement
data, Measurement system analysis, Calibration of measuring instruments, Principle of
air gauging- ISO standards.
UNIT 2 MEASUREMENT OF LINEAR, ANGULAR DIMENSIONS, ASSEMBLY AND
TRASMISSION ELEMENTS
• Linear Measuring Instruments – Vernier caliper, Micrometer, Vernier height gauge,
Depth Micrometer, Bore gauge, Telescoping gauge; Gauge blocks – Use and
precautions, Comparators – Working and advantages; Opto-mechanical measurements
using measuring microscope and Profile projector - Angular measuring instruments –
Bevel protractor, Clinometer, Angle gauges, Precision level, Sine bar, Autocollimator,
Angle dekkor, Alignment telescope. Measurement of Screw threads - Single element
measurements – Pitch Diameter, Lead, Pitch. Measurement of Gears – purpose –
Analytical measurement – Runout, Pitch variation, Tooth profile, Tooth thickness, Lead –
Functional checking – Rolling gear test.
UNIT 3 TOLERANCE ANALYSIS
• Tolerancing– Interchangeability, Selective assembly, Tolerance representation,
Terminology, Limits and Fits, ProblemsME(using
03/09/2024 3592 - MM tables IS919); Design of Limit gauges,
3
Problems. Tolerance analysis in manufacturing, Process capability, tolerance stackup,
UNITS
UNIT 4 METROLOGY OF SURFACES

• Fundamentals of GD & T- Conventional vs Geometric tolerance, Datums, Inspection of

geometric deviations like straightness, flatness, roundness deviations; Simple problems –
Measurement of Surface finish – Functionality of surfaces, Parameters, Comparative, Stylus
based and Optical Measurement techniques, Filters, Introduction to 3D surface metrology-
Parameters

UNIT 5 ADVANCES IN METROLOGY

• Lasers in metrology - Advantages of lasers – Laser scan micrometers; Laser interferometers
– Applications – Straightness, Alignment; Ball bar tests, Computer Aided Metrology - Basic
concept of CMM – Types of CMM – Constructional features – Probes – Accessories – Software
– Applications – Multi- sensor CMMs. Machine Vision - Basic concepts of Machine Vision
System – Elements – Applications - On-line and in- process monitoring in production -
Computed tomography – White light Scanners.
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 UNIT 1 – BASICS OF METROLOGY
• Measurement – Need, Process, Role in
quality control; Factors affecting
measurement - SWIPE; Errors in
Measurements – Types – Control –
Measurement uncertainty – Types,
Estimation, Problems on Estimation of
Uncertainty, Statistical analysis of
measurement data, Measurement system
analysis, Calibration of measuring
instruments, Principle of air gauging- ISO
standards
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WHAT IS METROLOGY?
• The word, “metrology,” is derived from Greek and essentially means the
study of measurement.

• Metrology originally stemmed from the need to manufacture

interchangeable parts. To make that possible, the dimensions of all the
parts had to fall within a specific range — otherwise, they simply wouldn’t fit
their companions.

• In its modern application, metrology has become a highly advanced field with
many tools and statistical methods to measure the accuracy and quality of
manufactured parts.
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WHAT IS MEASUREMENT?
• Measurement is the basic concept in the study of Mathematics and Science.
Measurement quantifies the characteristics of an object or event, which we can
compare with other things or events.

• Measurement is the most commonly used word, whenever we deal with the
division of a quantity. Also, in taking a certain amount of things to accomplish a
particular task.

• In our daily existence, we often come across different measurement types for
length, weight, times, etc. In this subject, you will learn the meaning and
definitions of measurement, along with types of measurement and examples.

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WHAT IS MEASUREMENT?

• Measurement is a technique in which the properties of an object

are determined by comparing them to a standard quantity. Also,
measurement is the essential metric to express any quantity of
objects, things and events.

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WHAT IS MEASUREMENT?

Measurement is a comparison of a give unknown quantity with

one of its predetermined standard values adopted as a unit

REQUIREMENTS FOR MEASUREMENTS

1. Standard must be accurate and internationally accepted

2. Instrument and the process used for measurement must be

provable
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FUNDAMENTAL MEASUREMENT
PROCESS

Comparis
Measuran
on Result
d
process

STANDARD

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NEED FOR MEASUREMENTS
• Measurement is crucial in various aspects of human life and across
different fields. Here are some key reasons why measurement is
essential:

• Quantification and Precision: Measurement allows us to quantify

and express the attributes or characteristics of objects, events, or
phenomena in a precise and standardized manner.

• It provides a common language for communication, ensuring that

everyone understands and interprets values consistently.
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NEED FOR MEASUREMENTS
• Scientific Research: In scientific research, accurate measurements
are essential for conducting experiments, collecting data, and
drawing meaningful conclusions. Precise measurements contribute to
the reliability and reproducibility of scientific studies.
• Engineering and Technology: In engineering and technology,
measurements are fundamental for designing, building, and testing
various products and systems. Engineers rely on measurements to
ensure the functionality, safety, and quality of their creations.
• Commerce and Trade: Measurement is crucial in commerce for
standardizing transactions and trade. Standard units of measurement
facilitate fair and transparent exchange of goods and services.
Accurate measurements prevent misunderstandings and disputes in
business transactions.
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NEED FOR MEASUREMENTS
• Healthcare: In healthcare, measurements are used for diagnosing
conditions, monitoring patient health, and administering treatments.
Vital signs, laboratory results, and other medical measurements help
healthcare professionals make informed decisions.
• Education: Measurement is a fundamental concept in education,
providing a basis for assessing and evaluating students’ progress and
achievements. Grading systems, standardized tests, and educational
assessments rely on measurements.
• Quality Control: In manufacturing and production, measurements
are crucial for quality control. They ensure that products meet
specified standards and comply with regulations. Precise
measurements help identify defects and improve the overall quality
of products.
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NEED FOR MEASUREMENTS
• Navigation: Measurements, such as distance and direction, are
essential for navigation. They are used in various fields, including
aviation, maritime, and land-based transportation.
• Environmental Monitoring: Measurement is vital for monitoring
environmental factors, such as air and water quality, climate
change, and biodiversity. Accurate measurements help in
understanding and addressing environmental issues.
• Personal and Everyday Life: In our daily lives, we use
measurements for cooking, construction, home improvement, and
various other activities. Measurements provide a basis for making
informed decisions, whether it’s choosing the right size clothing or
determining the right amount of ingredients for a recipe.

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TYPES OF MEASUREMENTS
Depending on the method, measurements are classified into two
types:
a) Direct measurement and b) Indirect measurement
1. Direct Measurement:
When measurements are taken directly using tools, instruments, or
other calibrated measuring devices, they are called direct
measurements.

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EXAMPLES OF DIRECT MEASUREMENTS
1. Length Measurement with a Ruler 9. Force Measurement with a Spring
2. Temperature Measurement with a Scale
Thermometer 10. Concentration Measurement with a
3. Mass Measurement with a Balance Spectrophotometer
11. Sound Level Measurement with a
4. Time Measurement with a Clock
Decibel Meter
5. Voltage Measurement with a
12. Electrical Current Measurement with
Voltmeter
an Ammeter:
6. Volume Measurement with a
Graduated Cylinder
7. Pressure Measurement with a
Pressure Gauge
8. Speed Measurement with a
Speedometer

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 INDIRECT MEASUREMENT
When the measurement must be done through a formula or
other calculations, the measurement is called indirect
measurement
1. Measurement of the radius of the Field Strength
Earth. 9. Estimating the Size of Atoms
2. Examples of Indirect Measurements: 10.Determining the Mass of Celestial
3. Distance Measurement using Bodies
Trigonometry 11.Indirect Measurement of Voltage in a
4. Determination of Acceleration Due to Circuit
Gravity 12.Indirect Measurement of Blood Flow
5. Estimating the Earth’s Circumference 13.Determining the Height of a Building:
6. Calculating Density
7. Determining the Speed of Sound
8. Indirect Measurement of Magnetic
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OTHER METHODS
1. Comparative method 7. Deflection method
2. Coincidence method 8. Substitution method
3. Fundamental method 9. Null method
4. Contact method measurement
5. Transposition method
6. Complementary
method

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GENERALIZED MEASURING SYSTEM
There are number of measuring instruments used in practice.
Therefore, it is necessary to identify the common features or the
basic elements of a generalized measuring system.
A generalized measuring system consists of the following
common elements:
1) Primary sensing element
2) Variable conversion element
3) Variable manipulation element
4) Data transmission element
5) Data processing element
6) Data presentation element
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 FUNCTIONAL ELEMENTS OF AN
INSTRUMENT SYSTEM

Physical Primary Variable Variable

variable to be sensing conversion manipulation
measured element element element

Data Data
observer presentation processing
element element

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 FUNCTIONAL ELEMENTS OF AN
INSTRUMENT SYSTEM
• PRIMARY SENSING ELEMENT

It is the first element which receives energy from the measured medium and
produces an output corresponding to the measurand. This output is then converted
into an analogous electrical signal by transducer.

• VARIABLE CONVERSION ELEMENT

It converts the output electrical signal of the primary sensing element (which may
be a voltage, frequency or some other electrical parameter) into a more suitable
form without changing the information content of the input signal. In some
instrument, there is no need of using variable conversion element while some other
instruments require variable conversion element.
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 FUNCTIONAL ELEMENTS OF AN
INSTRUMENT SYSTEM
• VARIABLE MANIPULATION ELEMENT

This element is used to manipulate the signal presented to it and preserving the
original nature of the signal.

In other words, it amplifies the input signal to the required magnification. For
example, an electronic voltage amplifier receives a small voltage as input and
produces greater magnitude of voltage as output.

A variable manipulation element does not necessarily follow a variable-

conversion element, it may precede it.

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DATA TRANSMISSION ELEMENT

It transmits the data from one element to the other. It may be as simple as shaft and gear assembly
system or as complicated as a telemetry system which is used to transmit signal from one place to
another.

DATA PROCESSING ELEMENT

It is an element which is used to modify the data before displayed or finally recorded. It may be
used for the following purposes:
• To convert the data into useful form.
• To separate the signal hidden in noise.
• It may provide corrections to the measured physical
variables to compensate for zero offset, temperature error, Scaling etc.
DATA PRESENTATION ELEMENT
The info of measured variable to a human observer for monitoring, control or analysis purpose. The
value of the measured variable may be indicated by an analog indicator digital indicator.
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 TEMPERATURE TEMPERATURE TABLE CAPILLARY TUBE

PRIMARY VARIABLE DATA

PHYSICAL VARIABLE
SENSING CONVERSION TRANSMISSION
TO BE MEASURED
ELEMENT ELEMENT ELEMENT

PRESSURE

DATA VARIABLE VARIABLE

OBSERVER PRESENTATION MANIPULATION CONVERSION
ELEMENT ELEMENT ELEMENT

SCALE AND POINTER LINKAGE AND GEAR SPIRAL BOURDON TUBE

MEASUREMENT SYSTEM OF A FILLED THERMAL SYSTEM

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ROLE OF METROLOGY IN QUALITY
CONTROL

• Metrology and quality control are essential for product accuracy

and consistency across all industries. Specifically, they ensure
that products adhere to requirements according to defined
standards.

• By using precise measurements, manufacturers can identify

abnormalities, make adjustments, and improve overall product
quality.

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ROLE OF METROLOGY IN
QUALITY CONTROL
• The manufacturing industry requires significant quality control to
avoid defects. Since metrology is the study of measurement, it is
the foundation for guaranteeing quality and accuracy.

• Regarding quality control, it helps products meet precise

specifications to create quality parts. Any inaccurate
measurement would cause the product quality to suffer.

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ROLE OF METROLOGY IN
QUALITY CONTROL
• Metrology and quality control have the same goal: consistent,
accurate measurements.

• To achieve consistency, trained technicians perform

measurements using calibrated instruments. These
specifications, in turn, help companies develop policies and
procedures for measuring their products to get consistent results
every time.

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ROLE OF METROLOGY IN
QUALITY CONTROL
• Generally, quality control requires accurate measurements
throughout the manufacturing process, from production to
inspection.

• Companies can take corrective action if necessary by measuring

a product and comparing those measurements against a
standard. Thus, preventing safety hazards, product failures, and
recalls.

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THE IMPORTANCE OF METROLOGY
IN QUALITY CONTROL
• Metrology provides the tools and methods to ensure products,
processes, and systems meet required standards. It does this in a few
ways:

1. REGULAR CALIBRATION

• Any measuring instrument or equipment needs regular calibration.

Calibration compares the measurements to a known standard to check
their accuracy, which is critical in quality control. When done regularly,
you can be confident that your readings are precise.
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THE IMPORTANCE OF
METROLOGY IN QUALITY
CONTROL
2. INSPECTION AND PRODUCT TESTING

• While inspection involves examining a product for defects, product

testing ensures the product is safe and effective. Checks can
happen at any time during the production cycle.

• Doing so allows inspectors to catch issues before they become part

of the final product. Whereas product testing lets manufacturers
know if their products work correctly after assembly.

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THE IMPORTANCE OF
METROLOGY IN QUALITY
CONTROL
3. DEVELOPMENT OF NEW PRODUCTS AND PROCESSES

• The ability to precisely measure something helps companies develop new products or
processes. These measurements then determine if parts fit together and meet specifications
as intended.

4. CONTINUOUS IMPROVEMENT

• To improve the quality of products, a company must know what it needs to refine.
Manufacturers can identify weak areas and enhance their existing products by measuring
performance.

• Thus, it has the advantage of reducing failure and increasing customer satisfaction. Reduction
in failure also reduces product/material waste and reduces overall manufacturing costs.

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FACTOR AFFECTING ACCURACY OF A
MEASURING SYSTEM

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FACTOR AFFECTING ACCURACY
OF A MEASURING SYSTEM
Standard
Normally the measuring instrument is calibrated with a standard
are at regular interval. The standard may be affected by
• Coefficient of thermal expansion
• Stability with time
• Elastic properties
• Geometric compatibility
• Position etc

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FACTOR AFFECTING ACCURACY
OF A MEASURING SYSTEM
• 2. Work piece: • 3. Instrument
The following factors affect the The inherent characteristics of the
accuracy instrument which affect the accuracy
• Cleanliness surface finish etc. are
• Inadequate amplification
• Surface defects
• Hidden geometry • Scale error

• Thermal equalization etc • Effect of friction backlash hysteresis

etc
• Deformation while handling heavy w/p
• Calibration error
• Repeatability and readability

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FACTOR AFFECTING ACCURACY
OF A MEASURING SYSTEM
• 4. Person in precision.
The factors responsible for accuracy
are
• 5. Environment
• Training skill
The environmental factor are:
• Sense of precision appreciation • Temperature press humidity
• Ability to select measuring instrument •
Clean surrounding and minimum
& standard
vibration
• Attitude towards personal accuracy • Adequate illumination
achievement
• Temperature equalization between
• Planning for measurement technique
standard w/p and instrument
to have minimum just with consistent

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SWIPE
• The operator, who has only his gage to go by, says, “Don’t tell me the parts
are no good-- they measure on my gage.” The inspector replies, “Well, the
parts don’t fit, so if your gage says they are okay, your gage is wrong.”

• This is the natural reaction. People are quick to blame the instrument
because it is easy to quantify. We can grab it, take it to the lab and test it.
However, this approach will often fail to find the problem, or find only part
of it, because the instrument is only one-fifth of the total measuring system.

• The five elements of a measuring system can be listed in an acronym.

SWIPE, and rather than immediately blaming the instrument when there is
a problem, a better approach is to examine all five elements:
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SWIPE
S STANDARD
W WORKPIECE BEING MEASURED
I INSTRUMENT
P PEOPLE
E ENVIRONMENT

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SWIPE
• S represents the standard used when the system is set up or checked for error,
such as the master in comparative gages of the leadscrew in a micrometer.
Remember, master disks and rings should be handled as carefully as gage
blocks, because nicks and scratches can be a significant contributor to error.

• W is the workpiece being measured. Variations in geometry and surface finish

of the measured part directly affect a system’s repeatability. These part
variations are difficult to detect, yet can sometimes manifest themselves as
apparent error in the measuring system. For example, when measuring a
centerless ground part with a two-jet air ring, a three-point out-of-round
condition will not show up because you are only seeing average size.

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SWIPE
• I stands for the instrument itself. Select a gage based on the tolerance of
the parts to be measured, the type of environment and the skill level of the
operators. And remember what your customers will be measuring the parts
with. Say, for example, you are checking bores with an air gage, but your
customer inspects them with a mechanical gage. Since the surface is not a
mirror finish, your air gage is giving you the average of the peaks and
valleys, while the customer’s mechanical gage is saying the bores are too
small because it only sees the peaks. Neither measurement is “wrong”, but
you could end up blaming each other’s instruments.
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SWIPE
• P is for people. Failure to adequately train operating personnel will ensure poor
performance. Even the operation of the simplest of gages, such as air gaging, requires
some operator training for adequate results. Most important, the machine operator
must assume responsibility for maintaining the instruments. Checking for looseness,
parallelism, nicks and scratches, dirt, rust, and so on, is absolutely necessary to ensure
system performance. We all know it, but we forget when we are in a hurry.

• E represents the environment. As is well know, thermal factors such as radiant energy,
conductive heating, drafts and room temperature differentials can significantly impact
gage system performance. And, again, dirt is the number one enemy of gaging. So the
problem that has you pulling your hair out and cursing your instruments could be as
simple as your shop being a little warmer or a little dustier than your customer’s
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 BEFORE BLAMING YOUR GAGE, TAKE A SWIPE AT IT
AND CONSIDER ALL THE FACTORS INFLUENCING ITS
ACCURACY.

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 ERRORS IN MEASUREMENT
Error:

Error is the difference between the measured

value and the true value.

Error in measurement = Measured Value -True value

The errors in measurement can be expressed either as

an absolute error or an relative error.

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ERRORS IN MEASUREMENTS
• Errors in Measurements are a common phenomenon in any method. The result of
every measurement done with the help of any measuring instrument contains some
uncertainty. This uncertainty is called error.

• In any physical or mathematical system, there is always a calibrated scale to measure

a physical quantity. When it is measured a numerical value is read from this predefined
scale.

• For example: when we measure the length of an object, we use a centimetre scale that
has pre-defined markings. This scale has the smallest division of 0.1 cm as shown
below in the diagram.

• This smallest division of scale is also known as its least count, thus the least count or
smallest division we can measure using centimetre scale is 1 mm.
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ACCURACY AND PRECISION

• Accuracy: The accuracy of a measurement is a measure of how

close the measured value is to the true value of the quantity.

• Precision: Precision refers to the closeness of two or more

measurements to each other. Precision tells us, to what resolution
or limit the quantity is measured.

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ACCURACY vs PRECISION

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ACCURACY vs PRECISION

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TYPES OF ERROR

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• Systematic Error: these are the errors due to the system.
Systematic error is further classified as
• Instrumental error: Errors that arise due to imperfect design or calibration
of the measuring instrument. Eg:
• Zero error in Vernier callipers emerges when the zero marks of the Vernier scale may not
coincide with the zero marks of the main scale,
• An ordinary meter scale may be worn off at one end.

• Error in measuring technique: To determine the temperature of a human

body, a thermometer placed under the armpit will always give a temperature
lower than the actual value of the body temperature.
• Personal errors: that arise due to an individual’s bias, lack of proper setting
of the apparatus or an individual’sMEcarelessness
03/09/2024 3592 - MM in taking down observations.
48
• Random errors: Random errors are those errors, which occur irregularly and hence
are random with respect to sign and size. These can arise due to random and
unpredictable fluctuations in experimental conditions. For example: if a person takes
multiple readings for the same experiment it is possible that every reading taken would
be unique and different from others.

• Least count error: The smallest value that can be measured by the measuring
instrument is called its least count. For example, a Vernier calliper has the least count
of 0.01cm; a spherometer may have the least count of 0.001 cm. Using instruments of
higher precision, improving experimental techniques, etc., we can reduce the least
count error.

• Gross error: These errors are due to either carelessness of the person or improper
adjustment of the apparatus. No corrections can be applied for gross errors.
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METHODS OF MINIMIZING
ERRORS
1. Proper calibration of instruments, apparatus and applying
corrections.

2. Improve experimentation techniques

3. Before starting any experiments, adjust the instrument to zero.

4. Take the measurements carefully.

5. The surrounding environment where the experiment is being

carried out can also cause an error.
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1. ABSOLUTE ERROR

The absolute error is classified into two types:

• TRUE ABSOLUTE ERROR

• APPARENT ABSOLUTE ERROR

i. TRUE ABSOLUTE ERROR:

Algebraic difference between the results of measurement to the true value of the
quantity measured is called true absolute error.

ii. APPARENT ABSOLUTE ERROR:

While taking the series of measurement, the algebraic difference between one of
the results of measurement to the arithmetic mean is called as apparent absolute
error.
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2. RELATIVE ERROR

Relative error is defined as the results of the absolute error and the
value of comparison used for calculation of that absolute error. The
comparison may be true value or conventional true value or
arithmetic mean for series of measurement.

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Types of Error
The errors can be classified into
1.Static errors
(i) Characteristic errors
(ii) Reading errors
(iii) Environmental errors
2. Loading errors
3. Dynamic error

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1. STATIC ERROR

It causes due to the physical nature of the various components of the

measuring system. The static errors due to environmental effect and
the other properties which influence the apparatus are also reasons
for static errors.

a) CHARACTERISTIC ERROR:
The deviation of the output of the measuring system from the
nominal performance specifications is called characteristic error. The
linearity, repeatability, hysteresis and resolution are part of the
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b) READING ERROR:

It is exclusively applied to the read out device. The reading error

describes the factors parallax error and interpolation error. The
use of mirror behind the readout indicator eliminates the
occurrence of parallax error. Interpolation error is a reading error
resulting from the evaluation of the position of index, The use of
digital readout device eliminates the subjective error.

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c) ENVIRONMENTAL ERROR

Every instrument is manufactured and calibrated at one place and

is used in some other place where the environmental conditions such

temperature, pressure, and humidity change. So, the change in environment

influences the readings of the Instrument. This change in environment is called
environment error. Following the below conditions, the environmental errors are
eliminated.

1. Monitoring the atmospheric conditions.

2. By calibration of instrument at the place of use.

3. Automatic devices are used to compensate the effects.

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CALIBRATION OF MEASURING INSTRUMENTS

• Calibration is a comparison of two instruments against each

other, one being the standard (the calibrator). This process is
essential to document the error of the instrument being
calibrated and to increase its accuracy.

• All instruments have errors and decreasing accuracies after a

certain amount of time. Calibration helps address these issues.

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WHY SHOULD YOU CALIBRATE YOUR
INSTRUMENTS?

• The biggest reason behind performing periodic calibration of

instruments is to test and ensure that they make correct and
accurate measurements.

• Regular calibration establishes efficient instrument performance,

safety during operations, long term sustainability, and high
instrument quality.

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WHY SHOULD YOU CALIBRATE
YOUR INSTRUMENTS?
• Timely action against drift

• All electric and electronic instruments drift over time with continuous usage.
Environmental conditions such as extreme temperature fluctuations,
changing weather, excess or lack of humidity can affect an instrument’s drift
too. In most instruments, greater usage means greater drift.

• In instruments requiring extreme accuracy and precision, drift can be highly

critical. Drift beyond the specified tolerance also poses a safety hazard. To
avoid these inaccuracies, it is important to perform periodic instrument
calibration.
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WHY SHOULD YOU CALIBRATE
YOUR INSTRUMENTS?
• Early detection of defects & damage

• Apart from drift, instruments are also prone to damage and defects
due to loose connections or faulty components. This damage can be
detected at an earlier stage with the help of calibration, and a total
breakdown of the instrument can be safely prevented.

• Once the defects are identified, the error propagation can be

minimized, reducing costs and resources of handling serious
damages.
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WHY SHOULD YOU CALIBRATE
YOUR INSTRUMENTS?
• Proactive Safety

• In industries such as oil and gas, petrochemical, chemical, energy,

power, electric, and electronic, there is a high risk of explosions, fires,
and leakages. The measurement equipment used in these industries
must be calibrated regularly and properly to avoid safety hazards and
ensure employee safety and infrastructure safety.

• In other industries such as pharmaceutical, food, and beverage, the

calibration of instruments is necessary for consumer/customer safety.
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Reputation of Quality

• Calibration is also important for social corporate responsibility, environmental and

financial reasons. Most companies and their customers have a quality system that
needs to be adhered to. Governments and regulatory bodies also lay down
conditions that need to be met to certify the company’s quality system, such as
emission monitoring and equipment testing.

• Measurement instruments used for these purposes should be highly accurate

which is why they need to be calibrated from time to time using calibration
techniques and equipment accredited to relevant ISO standards.

• Labs and test equipment companies that adhere to updated standards like
ISO/IEC17025:2017 establish their competence in quality management, improved
lab testing environments, better customer satisfaction, an international reputation,
& systematic processes.
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BENEFITS OF CALIBRATION
1. Some of the benefits of calibration are:
2. Long term cost-effectiveness, high return on investment
3. High instrument accuracy and precision
4. Reduction of costly errors
5. Longer instrument life
6. Compliance with regulatory standards and certification of
equipment
7. Elimination of safety risks
8. Less downtime for repair and maintenance of equipment
9. High customer satisfaction

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TYPES OF INSTRUMENT
CALIBRATION
Some of the common types of instrument calibration are:

• Humidity and Temperature Calibration

• It is used for businesses that use thermal cameras, thermometers,

humidity generators, weather stations, and other instruments with
their primary input as temperature and humidity.

• This type of calibration is carried out in closed environments to

eliminate disturbances from the surroundings and atmosphere.
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TYPES OF INSTRUMENT
CALIBRATION
• Pressure Calibration

• It is used for instruments such as transmitters, test gauges, and

barometers. In pressure calibration, the spectrum of hydraulic and gas
pressure is measured.

• Mechanical Calibration

• It is used for equipment such as torque wrenches, micrometers, scales,

and balances. Mechanical calibration calibrates for factors like force,
mass, vibration, or torque to ensure instrument accuracy.
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TYPES OF INSTRUMENT
CALIBRATION
• Electrical Calibration

• It is used for testing instruments such as clamp meters, data

loggers, and insulation testers. Equipment that measures
frequency, voltage, or resistance should undergo electrical
calibration.

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 HOW OFTEN SHOULD INSTRUMENTS BE
CALIBRATED?
• While there is no specific single to call attention to this need, there are some ways to
determine how often you should calibrate your instruments.

• The simplest thing to do is to follow the equipment manufacturer’s

recommendation. Manufacturers often provide specifications about a device’s
calibration and calibration period.

• Another important factor to consider is the measurement location criticality and

accuracy requirements.

• Some measurements require greater accuracy compared to others. The more critical
locations
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should be calibrated frequently, while the less critical locations can
ME 3592 - MM 67
be
HOW OFTEN SHOULD
INSTRUMENTS BE CALIBRATED?
• If an instrument is used often and is subjected to high workload and
extreme or harsh operating conditions, it is good practice to calibrate
often.

• The stability history of an instrument should also be factored in. If the

instrument has a demonstrated history of being stable, it can be
calibrated less frequently.

• On the other hand, if it has been shown to drift quickly, it should be

calibrated more often.
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03/09/2024 ME 3592 - MM 69
WHAT IS AIR GAUGING?
• Air gauging is a non-contact comparative measuring method. It has been
used in the industry for more than 80 years.

• The concept of air gauging is based on the law of physics that states flow and
pressure are directly proportionate to clearance and react inversely to
each other.

• Clearance in this case refers to the distance between the nozzle of the
air gauge probe and the workpiece.

• As clearance increases, air flow also increases, and air pressure decreases
proportionately. As clearance decreases, air flow also decreases, and air pressure
increases.
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AIR GAUGING

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PRINCIPLE OF AIRGUAGING
• Air gauging is highly suited for the measurement of soft, highly
polished, thin wallet, delicate components that require high
accuracy.

• The smaller the range, the better repeatability, up to a few

nanometers. A multitude of features can be measured by air:
inside and outside diameters, but also many geometrical features
such as taper, flatness, roundness, run-out, squareness,
straightness, etc.
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 PRINCIPLE OF AIRGUAGING
• This is made possible by having a regulated air flow through the nozzle in the air jets of
the air gauges.

• The nozzle acts as a restrictor. As the measured product is brought closer to the nozzle,
air flow is reduced, and the back pressure is increased.

• When the nozzle is completely obstructed, the flow is zero, and the back pressure is
equal to the regulated air. Conversely, when the nozzle is open to the atmosphere, air
flow is at a maximum, and the back pressure is at a minimum. The pressure
differences are then converted electronically to get an accurate dimensional
value.
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AIR GUAGING

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Who Uses Air Gauging?
• Air gauging is highly suited for the measurement of soft, highly
polished, thin wallet, delicate components that require high
accuracy.

• The smaller the range, the better repeatability, up to a few

nanometers.

• A multitude of features can be measured by air: inside and outside

diameters, but also many geometrical features such as taper,
flatness, roundness, run-out, squareness, straightness, etc.
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As a result, air gauging is used in many industries, they
include the following:
• Automotive
• Aerospace
• Bearings
• Medical
• Molds
• Machinery components
• Packaging
• and many others...

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What are the benefits of using air gauging for measurement?

• Ease of use, the operator will not be required to be specially trained to

use the equipment

• Operators will not be able to influence the results of the measurement

• Air gauging can be used to measure complex geometric tolerance

• High accuracy and repeatability

• Possible to measure parts without cleaning them first

• Technology particularly well suited to automation

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AIR GUAGING

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• One way external diameters are
measured with air gauges is using the
ring type air gauge. This is done by
inserting the part in an air jet ring
gauge.
• Normally, a guide is used to facilitate
the measurement of the components.
This is done to prevent the air jet ring
gauge from wearing out easily.
• Air gauges in snap gauges form are
also used for manual gauging. It is
used to mount into fixtures and for
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STANDARDS

• A standard is physical representation of a unit of measurement.

• A known accurate measure of physical quantity is termed as a standard.
• These Standards of Measurement are used to determine the values of
other physical quantities by the comparison method.

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 STANDARDS
• In fact, a unit is realized by reference to a material standard or to natural phenomena,
including physical and atomic constants.
• For example, the fundamental unit of length in the International system (SI) is the meter,
defined as the distance between two fine lines engraved on gold plugs near the ends of a
platinum-iridium alloy at 0°C and mechanically supported in a prescribed manner.
• Similarly, different standards have been developed for other units of measurement
(including fundamental units as well as derived mechanical and electrical units).
• All these standards are preserved at the International Bureau of Weight and Measures at
Sevres, Paris.
• Also, depending on the functions and applications, Different Types of Standards of
Measurement are classified in categories.
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TYPES OF STANDARDS

1.International Standards

2.Primary Standards

3.Secondary Standards

4.Working Standards

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International Standards
• International standards are defined by International agreement.

• They are periodically evaluated and checked by absolute

measurements in terms of fundamental units of Physics.

• They represent certain units of measurement to the closest possible

accuracy attainable by the science and technology of measurement.

• These International Standards of Measurement are not available to

ordinary users for measurements and calibrations.

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Primary Standards:
• The principle function of primary standards is the calibration and
verification of secondary standards. Primary standards are
maintained at the National Standards Laboratories in different
countries.

• The primary standards are not available for use outside the
National Laboratory. These primary standards are absolute
standards of high accuracy that can be used as ultimate
reference standards.
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Secondary Standards:
• Secondary standards are basic reference standards used by measurement and
calibration laboratories in industries.

• These secondary standards are maintained by the particular industry to which

they belong. Each industry has its own secondary standard.

• Each laboratory periodically sends its secondary standard to the National

standards laboratory for calibration and comparison against the primary
standard.

• After comparison and calibration, the National Standards Laboratory returns

the Secondary standards to the particular industrial laboratory with a
certification of measuring accuracy in terms of a primary standard.
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Working Standards:
• Working standards are the principal tools of a measurement laboratory.

• These standards are used to check and calibrate laboratory instrument

for accuracy and performance.

• For example, manufacturers of electronic components such as

capacitors, resistors, etc. use a standard called a working Standards of
Measurement for checking the component values being manufactured,
e.g. a standard resistor for checking of resistance value manufactured.

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