Industrial Process Measurement: Dimension Measurement

A Lecture on Dimension Measurement

1. Dimension measurement
By
Mr.Vuttichai Sittiarttakorn
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2. LECTURE OUTLINE
•1. Introduction
•2. Standards and Calibration
•3. Relative displacement : Translational and Rotational
•4. displacement transducers
•Potentiometers displacement sensors
•Inductive displacement sensors
•Capacitive displacement sensors
•Eddy current displacement sensors
•Piezoelectric displacement sensors
•Ultrasonic displacement sensors
•Optical encoder displacement sensors
•Strain Gages displacement sensors
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3. Introduction
•In physics and mathematics, the dimension of a
mathematical space (or object) is informally defined
as the minimum number of coordinates needed to
specify any point within it. Thus a line has a
dimension of one because only one coordinate is
needed to specify a point on it. A surface such as a
plane or the surface of a cylinder or sphere has a
dimension of two because two coordinates are
needed to specify a point on it. The inside of a cube,
a cylinder or a sphere is three-dimensional because
three coordinates are needed to locate a point within
these spaces.
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5. •In classical mechanics, space and time are different
categories and refer to absolute space and time. That
conception of the world is a four-dimensional space
but not the one that was found necessary to describe
electromagnetism. The four dimensions of space-time
consist of events that are not absolutely defined
spatially and temporally, but rather are known
relative to the motion of an observer.
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A well dimensioned part will communicate the size and
location requirements for each feature.
Communications is the fundamental purpose of
dimensions.
Parts are dimensioned based on two criteria:
Basic size and locations of the features.
Details of a part's construction and for manufacturing.

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Time
Time is a necessary component of many
mathematical formulas and physical functions. It is one
of several basic quantities from which most physical
measurement systems are derived. Others are length,
temperature, and mass.
We can see distance and we feel weight and
temperature, but we cannot apprehend time by any of
the physical senses.
WHAT IS TIME?
Time is a physical quantity that can be observed and measured
with a clock of mechanical, electrical, or other physical nature.

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10. Time measuring Instruments
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Sundial Clock Sand Clock
Mechanical ClockWater Clock

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12. DATE, TIME INTERVAL
AND SYNCHRONIZATION
•We obtain the date of an event by counting the number
of cycles, and fractions of cycles, of periodic events,
such as the Sun as it appears in the sky and the Earth’s
movement around the Sun, beginning at some agreed-
upon starting point.
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The important thing about measurement is that there
be general agreement on exactly what the scale is to be and
how the basic unit of that scale is to be defined. In other
words, there must be agreement upon the standard against
which all other measurements and calculations will be
compared.

13. UNITS OF TIME
•The basic unit for measuring time is the second. The
second multiplied evenly by 60 gives us minutes, or
by 3600 gives us hours. The length of days, and
even years, is measured by the basic unit of time, the
second. Time intervals of less than a second are
measured in l0 ths, 100 ths,1000 ths-on down to
billionths of a second and even smaller units.
•Each basic unit of measurement is very exactly and
explicitly defined by international agreement; each
nation directs a government agency to make
standard units available to anyone who wants them.
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14. Standard Clock
Caesium-133 : Frequency = 9,192,631,770Hz
National standards agencies in most industrialized and semi-
industrialized countries maintain an accuracy of 10
-9
seconds per day

15. Deep Space Atomic Clock
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NASA’s Deep Space Atomic Clock (DSAC) project is
developing a reduced size mercury ion atomic clock
that is as stable as a ground clock, small enough to
be hosted on a spacecraft, and able to operate in
deep space.

16. IEEE 1588 Standard for a Precision
Clock Synchronization Protocol
and Synchronous Ethernet
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Distribution of frequency and time over a
packet network (main focus on Ethernet)

17. •IEEE 1588 offers high accuracy (< 100 ns) over a
data network
•but requires hardware assistance is designed for
well-controlled LAN environment.
•Application of synchronized Clocks
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18. The Length Measurement Standard
•The Length -Evolution from Measurement Standard to
a Fundamental Constant explains the evolution of the
definition of the meter. Fromthe meter, several other
units of measure are derived such as the:
•unit of speed is the meter per second (m/s). The speed of
light in vacuum is 299 792 458 meters per second.
•unit of acceleration is the meter per second per second
(m/s
2
).
•unit of area is the square meter (m
2
).
•unit of volume is the cubic meter (m
3
). The liter (1 cubic
decimeter), although not an SI unit, is accepted for use
with the SI and is commonly used to measure fluid
volume.
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19. Unit definition
The meter was intended to equal one ten-millionth of the length
of the meridian through Paris from pole to the equator.
However, the first prototype was short by 0.2 millimeters
because researchers miscalculated the flattening of the earth due
to its rotation. In 1927, the meter was more precisely defined as
the distance, at 0°, between the axes of the two central lines
marked on the bar of platinum-iridium kept at the BIPM, and
declared Prototype of the meter by the 1st CGPM, this bar being
subject to standard atmospheric pressure and supported on two
cylinders of at least one centimeter diameter, symmetrically
placed in the same horizontal plane at a distance of 571 mm
from each other.
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21. •The 1889 definition of the meter, based upon the
artifact international prototype of platinum-
iridium, was replaced by the CGPM in 1960 using
a definition based upon a wavelength of krypton-86
radiation. This definition was adopted in order to
reduce the uncertainty with which the meter may
be realized. In turn, to further reduce the
uncertainty, in 1983 the CGPM replaced this latter
definition by the following definition:
•The meter is the length of the path travelled by
light in vacuum during a time interval of 1/299 792
458 of a second.
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22. Relative displacement
Calibration
-Static calibration via
micrometers 0.01mm
gauge blocks 12 micro-m
laser interferometer 0.6 nm
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25. Gauge Blocks
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26. Laser interferometer
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27. Displacement Sensors types
•Potentiometers displacement sensors
•Inductive displacement sensors
•Capacitive displacement sensors
•Eddy current displacement sensors
•Piezoelectric displacement sensors
•Ultrasonic displacement sensors
•Optical encoder displacement sensors
•Strain Gages displacement sensors
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28. Potentiometers displacement sensors
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29. Resistive Potentiometers (single-turn, multi-
turn, linear and rotating translation)
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30. Potentiometer loading effect (Linearity,
power loss)
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31. Construction of wire-wound resistance
(resolution)
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Linear variable differential transformer
(LVDT)

36. Differential Transformers
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37. Methods for Null Reduction
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38. LVDT

39. Strain gauge displacement transducers
and extensometer
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40. Industrial type LVDT
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41. LVDT Application
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42. Application
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43. Eddy current non-contact transducers
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45. Target-Material Effect on Eddy-
Current Transducer
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(a) Capacitance will vary with variation in dielectric constant
, (b) gap between plates and (c) area of capacitor's plates .

48. Differential-Capacitor Pressure
Pickup
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50. Piezoelectric Transducer
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51. Piezoelectric displacement sensors
•Piezoelectricity —the ability of certain materials to
develop an electric charge that is proportional to a direct
applied mechanical stress.
•The effect is reversible.
•Piezoelectric materials will deform (strain) proportionally
to an applied electric field.
•The effect is of the order of nanometers.
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52. Laser Dimensional Gauge
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53. Self-Scanning Diode Arrays and
Cameras
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54. Translational and Rotary Encoders
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55. Schematic diagram
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56. Translational and Rotary Encoders..
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57. Disk image form
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58. Translational and Rotary Encoders..
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59. Translational and Rotary Encoders…
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60. Output wave form of incremental
encoder
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61. Ultrasonic Displacement Transducer
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63. Average Velocity Measurement from
x/t : Hall-Effect Proximity Pickup
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