ppt on measurement and instrumentation

1. Debre Tabor University
Faculty of Technology
Department Of Mechanical Enginerring
Instrumentation and Measurement

2. 2

3. LECTUREOUTLINE
Introduction
Standard Units
Structure of measurement systems
Instrument types
Characteristics of instruments

4. MEASUREMENT, INSTRUMENTATION,
and METROLOGY
 The International Vocabulary of Basic and General
Terms in Metrology (VIM), has defined measurement
as “a set of operations having the object of determining
the value of a quantity”.
 In other words, a measurement is the evaluation of a
quantity made after comparing it to a quantity of the
same type which we use as a unit.
 Measurement is a process of gathering information
from a physical world and comparing this information
with agreed standards.
 It is carried out with instruments that are designed and
manufactured to fulfill given specifications.

5. Cont’d
 An instrument is a device that transforms a physical variable of
interest (the Measurand ) into a form that is suitable for recording
(the measurement ).
 Refers to a group of permanent systems which help us measure
objects and maintain retroactive control of a process.
 Are designed to maintain prescribed relationships between the
parameters being measured and the physical variables under
investigation.
 Measurand is the unknown quantity to be measured
 Metrology, the science and “grammar” of measurement is defined as
“the field of knowledge concerned with measurement”.
 It guarantees the meaning and validity of measurement by strict
accordance to established units.

6. Length:
 Throughout history units of length have been based
on pieces of the human body.
 ‘cubit’ is the oldest recorded measurement. It was first used
in Egypt about 5000 years ago. It was based on the distance
from a man’s elbow to the tip of his longest finger.
 ‘inch’ (2.5cm) comes from the roman word meaning ‘the
length from the knuckle of the thumb to the thumb nail’.
 ‘yard’: the standard of length in England decreed by the
king ‘it would be precisely equal to the distance from the
tip of his nose to the end of his outstretched arm’
 ‘Foot’: adopted by the French was the length of the
royal foot of King Louis XIV.

7. Cont’d
However, basing measurement units on body
sizes didn't work that well as people are different
sizes.
In 1960, an international committee established a
set of standards for the fundamental quantities of
science. It is called SI(System International) and
its units of length, mass, time, temperature,
electric current, luminous intensity and amount
of substance are the meter, kilogram, second,
kelvin, ampere, candela and the mole.

8. Basic International System of units(SI)
Cont’d

9. Cont’d

10. STANDARDS
• The performance of an instrument must be crosschecked
against a known device.
• In addition to primary international standards, standard
instruments are available having stable and precisely
defined characteristics that are used as references for other
instruments that are performing the same function.
• At a global level, checking is done by using an
international network of national and international
laboratories, such as the National Bureau of Standards
(NBS), the National Physical Laboratory (NPL), and the
Physikalisch-Technische Bundesanstalt of Germany.
Cont’d

11. STANDARDS ARE KEPT IN FOUR STAGES:
 International standard: represent certain units of measurement with
maximum accuracy possible within today's available technology. These
standards are under the responsibility of an international advisory
committee and are not available to ordinary users for comparison or
calibration purposes.
 Primary standards: are the national standards maintained by national
laboratories in different parts of the world for verification of secondary
standards. These standards are independently calibrated by absolute
measurements that are periodically made against the international
standards. The primary standards are compared against each other.
 Secondary standards: are maintained in the laboratories of industry and
other organizations. They are periodically checked against primary
standards and certified.
 Working standards: are used to calibrate general laboratory and field
instruments.

12. Cont’d
CALIBRATION OF INSTRUMENTS
 Calibration is a comparison of measuring equipment against a
standard instrument of higher accuracy to detect, correlate,
adjust, rectify and document the accuracy of the instrument
being compared.
 A test during which known values of Measurand are applied to
the transducer and corresponding output readings are recorded
under specified conditions.
 Calibration of an instrument is checked at several points
throughout the calibration range of the instrument.
 The calibration range is defined as “the region between the
limits within which a quantity is measured, received or
transmitted, expressed by stating the lower and upper range
values.” The limits are defined by the zero and span values.

13. CHARACTERISTICS OF A CALIBRATION
 Calibration Tolerance: Every calibration should be performed
to a specified tolerance.
 Tolerance: Permissible deviation from a specified value; may
be expressed in measurement units, percent of span, or
percent of reading.
 Accuracy Ratio: A good rule of thumb is to ensure an
accuracy ratio of 4:1 when performing calibrations.
 This means the instrument or standard used should be four
times more accurate than the instrument being checked.
 Therefore, the test equipment (such as a field standard) used
to calibrate the process instrument should be four times more
accurate than the process instrument, the laboratory standard
used to calibrate the field standard should be four times more
accurate than the field standard, and so on.

14. Enough for today!!!
Thank you!

15. Elements of Engineering Drawing
Engineering drawing are made up of graphics language
and word language.
Graphics
language
Describe a shape
(mainly).
Word
language
Describe size, location and
specification of the object.

16. Basic Knowledge for Drafting
Graphics
language
Word
language
Line
types
Geometric
construction Lettering
Projection
method

17. Traditional
Drawing Tools

18. TECHNICAL DRAWING BOARD

19. 1. T-Square 2. Triangles
DRAWING TOOLS

20. 3. Adhesive Tape 4. Pencils
2H or HB for thick line
4H for thin line
DRAWING TOOLS

21. 5. Sandpaper 6. Compass
DRAWING TOOLS

22. 7. Pencil Eraser 8. Erasing Shield
DRAWING TOOLS

23. 9. Circle Template 10. Tissue paper
DRAWING TOOLS

24. 11. Sharpener 12. Clean paper
DRAWING TOOLS

25. Drawing Standard

26. Introduction
Standards are set of rules that govern how technical
drawings are represented.
Drawing standards are used so that drawings convey
the same meaning to everyone who reads them.

27. Drawing Sheet
Trimmed paper of
a size A0 ~ A4.
Standard sheet size
(JIS)
A4 210 x 297
A3 297 x 420
A2 420 x 594
A1 594 x 841
A0 841 x 1189
A4
A3
A2
A1
A0
(Dimensions in millimeters)

28. Drawing space Drawing
space
Title block
d
d
c
c
c
Border
lines
1. Type X (A0~A4) 2. Type Y (A4 only)
Orientation of drawing sheet
Title block
Sheet size c (mm) d (mm)
A4 5 20
A3 5 20
A2 10 25
A1 20 25
A0 20 25

29. SAMPLE OF DRAWING SHEET

30. Drawing Scale

31. Drawing Scales : Definition
Drawing Actual
Length, size
:
Scale is a ratio between the linear dimension of a
drawn representation of an object and the actual object.
1 2

32. Drawing Scales
Designation of a scale consists of the word “SCALE”
followed by the indication of its ratio, as follow
SCALE 1:1 for full size
SCALE X:1 for enlargement scales (X > 1)
SCALE 1:X for reduction scales (X > 1)
Dimension numbers shown in the drawing are correspond
to “true size” of the object and they are independent of
the scale used in creating that drawing.

33. Drawing Standard
Lettering
Drawing standard Contents

34. - Size (or text height)
- line thickness
- Shape
- Space between letters
- Space between words
Recommendation
Legibility
Uniformity
Text’s style on the drawing
must have the following
2 properties
Examples
GOOD
Not uniform in style.
Not uniform in height.
Not uniformly vertical.
Not uniform in
thickness of stroke.
Inappropriate space
between letters

35. Style (this course)
Gothic vertical style.
Begin the sentence, phrase or word with a capital letter.
Text height 2~3 mm.
Space between lines of text is about of text height.
Height of the lower-case letter is about 2/3 of that of a
capital letter.

36. The title block should include:
Title:- title of the drawing
Name:- name of the person who produced the drawing,
Checked before manufacture, drawings are usually
checked
Date:- the date the drawing was produced or last
amended
Notes:- any note relevant to the drawing
Scale:- the scale of the drawing
Company name:- name of the company
Projection:- the projection system used to create the
drawing
Title block

37. All engineering drawings should feature a
title block.

38. Bill of material
Part list (or bill of materials, BOM) consists
1. Item number
2. Descriptive name
3. Material, MATL.
4. Quantity required (per a unit of machine),
QTY
5. Dimensions

39. GENERAL ASSEMBLY