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EPM 212 METROLOGY &

QUALITY CONTROL(METROLOGY component)

Objective of course

To learn the basic concepts in

dimensional metrology, working principles

and applications of precision measurement

tools

LEARNING OUTCOME TOPICS/TEACHING PLAN HOURS

Able to explain the various

measurement terminologies and

standards in metrology

Introduction and basic concepts 1

Measurement errors 1

Measurement standards 3

Able to:

(i) Explain the working principles of

vernier and micrometer instruments

(ii) Determine flatness and

parallelism using optical flats

(iii) Determine surface roughness

and roundness of machined parts

(iv) Measure part dimensions using

coordinate measuring machine

(v) Interpret GD&T symbols

(vi) Perform GR&R analysis on

measurement data

Linear and angular

measurement

4

Roughness and roundness

measurement

4

Machine tool metrology 1

Coordinate metrology 1

GD&T 3

Gage repeatability & reliability 2

Test 1

Total 21(14x3/2 = 21 hrs)

LEARNING OUTCOMES Assessment method:

Coursework: 40%

Examination: 60%

Metrology: 20% Quality Control: 20%

Quiz: 6%

Lab./viva: 4%

Test: 10%

First 10 minutes

References:

1. Fundamentals of Dimensional Metrology

- Ted Bush, Roger Harlow

2. Metrology for Engineers

- J. F.W Gayler, C. R. Shotbolt

3. Pengenalan Metrologi Dimensi

- R. Mani Maran

Course module:

EPM212 Metrology & Quality Control

- Mani Maran Ratnam

Course handouts and slides:

Download from : e-learning

Class schedule

Week 1 to Week 7: Metrology

Week 8 to Week 14: Quality Control

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1.0 Introduction and Basic Concepts

Learning Outcomes

At the end of this topic, you should be able to:

1.Distinguish the various terminologies in metrology, such as accuracy, precision, resolution, sensitivity, repeatability, reproducibility, tolerance etc.

2.Determine, among a given set of instruments, which has the highest precision, lowest precision, highest accuracy & lowest accuracy

1.0 Introduction and Basic Concepts

1.1 Definition of Metrology

Metrology science of measurement

Dimensional metrology

Metrology involves design, manufacture, testing of

gages and instruments, as well as industrial

inspection and measurement

http://www.mitutoyo.com.sg/

Three reasons:

Why do we need measurements?

1.2 The Need for Measurement and Inspection 1.3 Job of a metrologist

Develop and evaluate calibration systems

Identify error sources in measurement

Develop calibration methods

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1.4 Terminologies in metrology

Precision: Repeatability of a measurement

when carried out using the same standard

1.4.1 Precision and Accuracy

Measured value

22.890 mm

23.010 mm

22.950 mm

23.008 mm

22.880 mm

23.002 mm

Readings

Mean

Accuracy: Degree of closeness of measured

values with actual dimension

Measured value

22.890 mm

23.010 mm

22.950 mm

23.008 mm

22.880 mm

23.002 mm

20 mm

Readings

Mean

20 mm

Error

Mean value

Actual dimension

Error

Measurements

Reading

Error

Reading

Mean value

Actual dimension

Measurements

1.4.2 Error

Error: Difference between measured value and

actual value

- correction to be made to the reading to

obtain actual value

Lets think

What is the difference between error and accuracy?

Error Accuracy

Known after measurement

Predicted before measurement

Either postive or negative

Has both positive and negative signs

Sometimes, can be corrected

Intrinsic part of the instrument

Factors that affect accuracy of measurement:

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Resolution: Smallest dimension that can be

measured using an instrument

Sensitivity: Minimum input that will produce

an output that can be detected

1.4.3 Resolution and Sensitivity 1.4.4 Range and Span

Range: Limits between which the input

parameter can vary

Span: Difference between the maximum and

minimum reading

Repeatability: Closeness between readings

from a sequence of measurements of the same

dimension under the same measuring condition

Reproducibility: Closeness between readings

from a sequence of measurements of the same

dimension under different measuring condition

1.4.5 Repeatability and Reproducibility

Uncertainty: Likely upper bound on the magnitude

of error

1.4.6 Uncertainty and Tolerance

Tolerance: Variations of a dimension allowed on a part

E1 < error < E2

E1 < measured - actual < E2

measured E2 < actual < measured E1

1.5 Measurement standards

1.5.1 Historical perspective of length standard:

4000 BC : Common length standard in Egypt was the

Kingss elbow (1 elbow = 1.5 feet, 2 handspan, 6

handwidths, 24 finger-thicknesses)

1101 : King Henry I declared a new standard yard - the

distance from his nose to the tip of his thumb

1528 : French physician, J. Fernel, proposed the

distance between Paris and Amiens as the length

reference

Historical perspective of length standard (ctd.):

1661 : British architect, Sir Christopher Wren suggested

the length of a pendulum with period of 1/2 s as the

standard

1790 : The concept of meter was introduced - gage

block of 1 meter made of pure platinum

1872 : International committee decides on international

meter standard - engraved on a new bar made from

platinum-iridium

1960 : The meter was officially defined based on the

wavelength of light

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One meter is defined as 1650763.73 where

is the wavelength of orange-red radiation

of krypton-86 isotope

= 605.78 nm

The Seventeenth General Conference on

Weights and Measures redefined the meter

directly in terms of the speed of light:

The meter is the length of the path traveled

by light in vacuum during a time interval of

1/299,792,458 of a second.

Physical Quantity Name Unit

1. Length

2. Mass

3. Time

4. Electric current

5. Temperature

6. Luminous intensity

7. Amount of substance

8. Plane angle

9. Solid angle

Basic Quantities in SI system

Activity 1 (3 minutes)

I. Precision of A is higher than precision of B?

II. Accuracy of A is higher than accuracy of B?

III. Sensitivity of A is higher than sensitivity of B?

IV. Resolution of A is higher than resolution of B?

Test your knowledge

What is the difference between the dial indicators shown:

A B

Three digital calipers A, B and C were used to

measure the length of a gage block of nominal length 20

mm. Five readings were recorded for each caliper. The

readings taken are as follows:

Digital caliper Readings (mm)

A 20.05, 20.08, 19.99, 20.02, 20.06

B 20.15, 20.16, 20.14, 20.15, 20.16

C 19.23, 19.44, 20.00, 21.02, 19.03

Which caliper has the :

(a) highest accuracy?

(b) lowest accuracy?

(c) highest precision?

(d) lowest precision?

Activity (15 minutes) Learning Points

1. What is the difference between precision and

accuracy?

2. What is meant by resolution?

3. What is meant by uncertainty?

4. What is meant by tolerance?

5. What is the difference between precision and

repeatability?