Download 05-2-SI units , hassan bani amer

MEASUREMENT
S.I. UNITS
• system International units
• A modification of the older French metric
system.
Base Units
Base units they are not derived from
any pre-existing number or
formula. like distance, temperature
and time, and we do so by agreeing
to a reliable definition of some
basic facts.
Base Units
•Length
Base Units
•Length
Meter
Base Units
•Length
Meter
(m)
Base Units
•Mass
Base Units
•Mass
Kilogram
Base Units
•Mass
Kilogram
(kg)
Base Units
•Time
Base Units
•Time
Seconds
Base Units
•Time
Seconds
(s)
Base Units
•Temperature
Base Units
•Temperature
Kelvin
Base Units
•Temperature
Kelvin
(K)
Base Units
• Amount of Substance
Base Units
• Amount of Substance
mole
Base Units
• Amount of Substance
mole
(mol)
Base Units
•Electric Current
Base Units
•Electric Current
Ampere
Base Units
•Electric Current
Ampere
(A)
Base Units
•Luminous Intensity
Base Units
•Luminous Intensity
candela
Base Units
•Luminous Intensity
candela
(cd)
Derived Units
•Area
First Derivative
•Area
length squared
Derived Units
•Area
length squared
2
(m )
Second Derivative
•Volume
Second Derivative
•Volume
length cubed
Second Derivative
•Volume
length cubed
3
(m )
Derived Units
•Density
Derived Units
•Density
mass per unit volume
Derived Units
•Density
mass per unit volume
3
(kg/m )
First Derivative
•Speed (velocity)
Derived Units
•Speed (velocity)
distance traveled per unit time
Second Derivative
•Speed (velocity)
distance traveled per unit time
(m/s)
Third Derivative
•Acceleration
Third Derivative
•Acceleration
speed changed per unit time
Derived Units
•Acceleration
speed changed per unit time
2
(m/s )
Derived Units
•Force
Derived Units
•Force
mass times acceleration of an object
Derived Units
•Force
mass times acceleration of an object
(kg
2
m/s )
Derived Units
•Force
• Note:
(kg
2
m/s )
= Newton (N)
Derived Units
•Pressure
Derived Units
•Pressure
Force per unit area
Derived Units
•Pressure
Force per unit area
(kg /m
2
s)
or
2
N/m
Derived Units
•Pressure
Note:
(kg /m s2) = N/m2 = Pascal (Pa)
Derived Units
•Energy
Derived Units
•Energy
Force times distance traveled
Derived Units
•Energy
Force times distance traveled
(kg
2
m
2
/s )
Derived Units
•Energy
Note:
(kg
2
m
2
/s )
= Joule (J)
Other Units to Know About
• Length
–Angstrom (Å) = 10-10m
Other Units to Know About
• Temperature
3 common scales
Fahrenheit
Celsius
Kelvin
Temperature
Freezing Pt
Boiling Pt
32 °F
212 °F
0 °C
100 °C
273.15 K 373.15 K
Temperature
• Formulas for converting scales
°C + 273.15 = K
1.8(°C ) + 32 = °F
Other units to know about
• Volume
Liter (l) = 1 dm3
3
1 ml = 1 cm
STANDARDS OF MEASUREMENT
• The standards of measurements are very
useful for calibration of measuring
instruments. They help in minimizing the
error in the measurement systems.
• The difference types of standards of
measurement and classified by their
function and application in the category :
1. Primary Standards
2. Secondary standards
3. Working standards
Primary Standard
A primary standard quantity will have only one value
and it is fixed. An instrument which is used to
measure the value of primary standard quantity is
called primary standard instrument. It gives the
accurate value of the quantity being measured. No
pre-calibration is required for this instrument. It is
used to calibrate the instruments having less accuracy.
By comparing the readings of the two instruments, the
accuracy of the second instrument can be determined.
Secondary Standard
The value of the secondary standard quantity
is less accurate than primary standard one. It
is obtained by comparing with primary
standard. For measurement of a quantity using
secondary standard instrument, pre-calibration
is required.
• Without calibration, the result given by this
instrument is meaningless. Calibration of a
secondary standard is made by comparing
the results with a primary standard
instrument or with an instrument having
high accuracy or with a known input source.
In practical fields, secondary standard
instruments and devices are widely used.
Working standards:
These standards are similar in design to
primary & secondary standards.
But being less in cost and are made of low
grade materials, they are used for general
applications in metrology laboratories.