3. Measurement
Measurement means to compare something
with standard.
E.g. measuring length of a wire, diameter of a
cylinder, depth of any object.
The SI unit of length is meter (base unit).
Its multiples and sub-multiples are given in
the table.
4. Meter and its sub-multiples
Prefix Symbol
Relationship with
Meter (base unit)
meter m 1m = 1 m
deci dm 1dm = 10-1
m
centi cm 1cm = 10-2
m
milli mm 1mm = 10-3
m
micro µm 1 µm = 10-6
m
nano nm 1nm = 10-9
m
pico pm 1pm = 10-12
m
5. Meter and its multiples
Prefix Symbol
Relationship with
meter
deca da 1 dam = 101
m
hecto h 1 hm = 102
m
kilo k 1 km = 103
m
mega M 1 Mm = 106
m
giga G 1 Gm = 109
m
6. Measuring Tools
Vernier caliper
Vernier caliper is a measuring device used to measure
precise increments between two points.
Micrometer
Micrometer is a measuring device used for precisely
measuring thickness, inner and outer diameter, depth of
slots.
SWG
A gauge for measuring the diameter of wire, usually
consisting of a long graduated plate with similar slots
along its edge.
7. Vernier caliper
Function
To measure smaller distances
Can measure up to .001 inch or .01mm.
Features
Larger, lower jaws are designed to measure outer points
e.g. diameter of a rod.
Top jaws are designed to measure inside points e.g. size of
a hole.
A rod extends from the rear of the caliper and can be used
to measure the depth.
9. Structure of the Vernier caliper
Main Scale
Main scale is graduated in cm and mm.
Vernier Scale
It slides on the main scale.
On Vernier scale 0.9cm is divided into 10 equal parts.
Jaws
Two inside jaws (Upper)
Two outside jaws (Lower)
10. Least Count
Least count (L.C) is the smallest reading we can
measure with the instrument.
L.C = one main scale division – one
vernier scale division
L.C = 1mm – 0.09mm
L.C = 0.1mm = 0.01cm
Least Count = Value of the smallest division on MS/
Total number of division on VS
L.C = 1mm / 10 = 0.1 cm / 10 = 0.01cm
11. How to use Vernier caliper?
• Close the jaws
• Calculate the least count
• Place the object between
the two jaws
• Record the position of zero
of Vernier scale on the Main
scale (3.2cm)
• Notice the reading of VS
which coincides with MS
reading (3rd
division in this
case)
12. Reading of the Instrument
Reading of the instrument = MS div +
(coinciding VS div x L.C)
= 3.2 + (3 x 0.01)
= 3.2 + 0.03
= 3.23 cm
14. To measure the depth
A rod extends from the rear of the caliper and
can be used to measure the depth.
Open the jaws of caliper and place the rod
inside hole of the object, such as the rod
reaches the inner most portion of the object.
Read the Vernier caliper. (same procedure as
described in previous slides)
15. Micrometer
Function
Micrometer allows the measurement of the size of the body
i.e. thickness, depth, inner/outer diameter.
Features
Two jaws (one fixed, one movable)
Spring loaded twisting handle
Easy to use and more précised
Can measure up to .001cm
17. Structure of Micrometer
Jaws
2 jaws (one fixed, one movable)
Circular Scale
Movable jaw is attached to a screw, scale on this screw is
called Circular scale.
Either 50 or 100 divisions
Linear Scale
Horizontal Scale
18. Structure of Micrometer
Frame
The C-shaped body that holds the anvil and sleeve in constant relation to
each other.
Anvil
The jaw which remains stationary.
Spindle
The jaw which moves towards the anvil.
Lock Nut
A lever, one can tighten to hold the spindle stationary.
Sleeve
The stationary round part with the linear scale on it. (Main Scale)
Thimble
Thimble rotates around the sleeve.
Ratchet Stop
Device on end of handle that limits applied pressure by slipping at a
calibrated torque.
19. Pitch of Micrometer
When the head of the micrometer rotate
through one rotation, called pitch of the
micrometer.
The screw moves forward or backward 1mm
on the linear scale.
Pitch of Micrometer = distance on linear
scale / one rotation
Pitch of Micrometer = 1/1 = 1mm
20. Least Count
Least Count = Pitch of the Micrometer / Total
number of circular scale division
Least Count = 1 / 100 = 0.01mm
= 0.001cm
21. How to use Micrometer?
• Thimble
– The thimble rotates around a
cylinder which is marked in
millimeters.
– The left-hand side of the
thimble has markings all
around it.
– The line labeled 0 is the
primary pointer.
• Close the jaws
• Calculate the least count
• Place the object between the
two jaws
• Record the position of main
scale where the two measuring
rods met.
• Note the position of the circular
scale which coincides with
main scale
22. Reading of the Instrument
Reading of the instrument = MS div +
(coinciding CS div x L.C)
= 8+ (12 x 0.01)
= 8 + 0.120mm
= 8.120 mm = 8120 µm
23. Standard Wire Gauge (SWG)
A gauge for measuring the diameter of wire, usually
consisting of a disk having variously sized slots in its
periphery or a long graduated plate with similar slots
along its edge.
A standardized system of wire sizes.
Wires are manufactured to standard sizes and
labeled with their SWG.
As the SWG increases the diameter decreases.
