DEE2313
Instrumentation &
Measurements
Nor Hadzfizah Mohd Radi
Faculty of Electrical & Electronics
Engineering
1
About this course
o 3 credit hours
o Class meets 3hrs per week
Mon (9:00am – 10:50am)
Thu (10:00am – 10:50am)
o Laboratory
Fri (3:00pm – 4:50pm)
2
Course Synopsis
This course introduces the principles of
instrumentation and measurements. It
explores the working principles of DC &
AC meters, oscilloscope and signal
generators as well as the operation and
application of various sensors and
transducers
3
Objectives
o Introduce the fundamentals of
measurements and instrumentation
o Explain the working principle of DC & AC
meters and measurements
o Discuss the operation of oscilloscope and
signal generator
o Describe the working principle of various
sensors and transducers
o Explain the methodology of signal
conditioning and data acquisition
4
Outcomes
o Able to
Explain the fundamentals of measurements
and instrumentation
Explain the working principle of DC & AC
meters
Discuss the operation of oscilloscope and
signal generator
Describe the working principle of various
sensors and transducers
5
Syllabus - Topics
• Part 1
– Measurements
• Part 2
– DC Measurement
– Instrumentation
– AC Measurement
– Signal conditioning
– Oscilloscope
– Signal transmission
– Signal generator
– Sensors
6
References
o Northrop R.B., Introduction to Instrumentation
& Measurement, 2nd Ed., CRC Press, 2005
o Morris A.S., Measurement & Instrumentation
Principle, Butterworth-Heinemann, 2001
o Kalsi H.S., Electronic Instrumentation, 2nd Ed.,
Tata McGraw-Hill, 2004
7
Assessments
• Notes
• Distribution
– Final Exam
– Test 1 & 2
– Quiz
– Laboratory
(40%)
(30%)
(10%)
(20%)
– Quiz – series of
short/pop
quizzes
– Laboratory –
preliminary work
& experiment
report
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Chapter 1
Introduction to
Instrumentation and
Measurements
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Measurement?
• Process of comparing an unknown
quantity with an accepted standard
quantity
• Estimation of the magnitude of some
attribute of an object relative to a unit
of measurement
10
Principle of Measurement
•
•
•
•
Measurement standards
Measurement errors
Accuracy vs. precision
Measurement Uncertainty
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Measurement Standards
• Based on definition of the seven
fundamental SI units of measurement
• Categorized into four:
– International standard (SI)
– Primary standards
– Secondary (transfer) standards
– Working standards
12
Base Units of Measurement
Quantity
Length
Symbol
l
Unit
Symbol
meter
m
Mass
m
kilogram
kg
Time
t
second
s
Temperature
T
kelvin
oK
Electric current
I
ampere
A
Amount of Substance
mole
mol
Luminous intensity
candela
cd
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Electrical Units
Quantity
Symbol
Unit
Unit Abbre.
Voltage (emf)
V
volt
V
Charge
Q
coulomb
C
Resistance
R
Ohm
Ω
Capacitance
C
farad
F
Inductance
L
henry
H
• Above electrical units are derived from standard
unit of measure for electric current
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Measurement Errors
• Deviation of a reading from the
expected value of the measured
variable
• Extent of measurement error must be
stated with the measurement
• Error in measurement is expressed as
absolute error or percentage of error
15
Error Calculation
Absolute error (e)
The difference
between the
expected (Yn) and the
measured (Xn) value
of a variable
Percentage of error
Percent error =
Yn - Xn
(100)
Yn
e = Yn - Xn
16
Source of Error in Measurement
• Divided into four categories:
–Gross Errors
–Systematic Errors
–Random Errors
–Limiting Errors
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Gross Errors
• Generally the fault of the person using
the measuring instrument such as
incorrect reading, incorrect recording,
incorrect use etc
• Avoidable and must be identified and
minimized if not eliminated
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Systematic Errors
• Probable causes:
– Instrument error
– Environmental effect
– Observational errors
• Causes shall be identified and
corrected
19
Random Errors
o Generally an accumulation of large
numbers of small inherent causes
o Shall be statistically analyzed and
reduced
o Prompt for better accuracy and
precise instrument
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Limiting Errors
o Manufacturing limitation to the
accuracy of an instrument
o Stated as percentage of full-scale
deflection
o Increases as measured value less
than full-scale deflection
21
Limiting Errors (cont’d)
• Example:
A 300-V voltmeter is specified to be accurate within
±2% at full scale. Calculate the limiting error when
the instrument is used to measure a 120-V source.
The magnitude of the limiting error is
2/100 x 300 = 6V
Therefore, the limiting error at 120 V is
6/120 x 100 = 5%
(reading < full scale, limiting error increased)
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Accuracy vs. Precision
• Accuracy
• Precision
– The degree of exactness
of a measurement
compared to the
expected value
A=1-
Yn - Xn
Yn
– A measure of consistency,
or repeatability of
measurements
Precision = 1 - Xn - Xn
Xn
Xn = the value of the nth measurement
X n = the average of the set of n
measurements
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Example
The expected value of the voltage across a resistor
is 5.0V. However, measurement yields a value of
4.9V. Calculate:
a) absolute error (0.1)
b)% error (2%)
c) relative accuracy (0.98)
d) % accuracy (98%)
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Measurement Uncertainty
• Probability that a reading falls within
the interval that contain true value
• Confidence level for margin of errors
• Statistically determined
• Reflect instrument imprecision
25
Statistical Analysis of Error in
Measurement
oMean value/ Arithmetic Mean
oDeviation
oAverage deviation (D)
oStandard deviation (S)
26
Arithmetic mean/average
n
x1  x 2  x 3    x n
xi
x

n
i 1 n
n
= total number of piece of data
xn
= the value of the nth measurement
xi
= set of number
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Deviation
• The difference between each piece of
data and arithmetic mean
d n  xn  x
* Note
dtot  d1  d 2    d n  0
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Average deviation (D)
• precision of a measuring instrument
- high D low precision
- low D  high precision
D
d1  d 2    d n
n
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Standard deviation (S)
• The degree to which the value vary about the
average value
n
S
 xi  x 
n
2
i 1
n 1

2
d
 i
i 1
n 1
for n  30
n
S
2
d
 i
i 1
n
for n  30
30
Example
For the following data compute
(a) The arithmetic mean (49.9)
(b) The deviation of each value (0.2,-0.2,-0.3,0.3)
(c) The algebraic sum of the deviation (0)
(d) The average deviation (0.25)
(e) The standard deviation (0.294)
x1= 50.1
x2= 49.7
x3= 49.6
x4= 50.2
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Calibration
• Process of establishing the relation
between the indication of a measuring
instrument and the value of a
measurement standard
• Traceability to International Standard
• Calibration improve accuracy
32
THE END
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