Abstract
Objective:
1) To be familiar with the concept of linear measurement and what is the tools
used for this type of measurements.
2) Be able to read any measurement device.
3) To use different types of linear measurement devices (Calipers and
micrometers) and find their accuracy and uncertainty.
4) Compare the measured results of each device with the results of other
measuring devices.
Procedure :
1) Check that you can handle all the measurement devices and can read it
correctly.
2) Check the tools you want to use, check their accuracy and zero alignment.
3) Clean the specimen to me measured.
4) Hold the tool in the appropriate way to start measuring.
5) Measure the dimensions of the specimen with all the measuring devices and
record the readings.
Results:
Measuring
instrument
Vernier
caliper
Dial caliper
Outside
micrometer
Depth
Micrometer
D1
D2
D3
D4
Da
Db
Dc
Dd
H1
H2
H3
H4
19.6
24.2
30.2
42.2
8.21
-
20.45
33.25
14.17
13.8
31.2
72.8
19.15
19.12
24.25
24.17
30.30
30.26
40.40
42.37
20.80
33.40
-
-
14.80
18.70
30.50
73.35
15.2
10.14
31.27
72.72
Objectives:
To familiarize the student with the types, applications of calipers, micrometers
and measurements.
At the completion of this experiment the student will be able to.
1) Get familiar the variety of the linear measurement tools, and know the type
of a measurement tool needed to achieve a certain measurement.
2) Students will seek more efficient means of measure.
3) Take linear measurements with a certain accuracy depending on the
instrument being used.
4) Clean, care for and store calipers, micrometers and dial indicators.
Experimental setup:
1 - Outside jaws: used to take external measures of
objects
2 - Inside jaws: used to take internal measures of
objects
3 - Depth probe: used to measure the depth of
objects
4 - Main scale (cm)
5 - Main scale (inch)
6 - Vernier (cm)
7 - Vernier (inch)
8 - Retainer: used to block movable part
Figure 1.1 Vernier Caliper.
Figure 1.2 Dial Caliper.
Figure 1.3 Micrometer.
Figure 1.4 Depth Gauge Micrometer.
Data collected:
Measuring
instrument
Vernier
caliper
Dial caliper
Outside
micrometer
Depth
Micrometer
D1
D2
D3
D4
Da
Db
Dc
Dd
H1
H2
H3
H4
19.6
24.2
30.2
42.2
8.21
-
20.45
33.25
14.17
13.8
31.2
72.8
19.15
19.12
24.25
24.17
30.30
30.26
40.40
42.37
20.80
33.40
-
-
14.80
18.70
30.50
73.35
15.2
10.14
31.27
72.72
Discussion and conclusion:
Caliper:
1) Does the vernier caliper conform to abbe’s principle of alignment? Why?
vernier caliper does not because the graduations are not on the same axis as
the measurement.
2) Calculate the error of a vernier caliper
Accuracy = least reading in the main scale /no. of division on the vernier scale.
3) What is the function of the sliding blade of the caliper?
Gives the least significant digits in the reading a subdivides a mark on the
main scale into 10,20,30 subdivisions.
4) What is a direct reading instrument ? does this apply to the caliper ?
These instruments permit real-time or near real-time measurements and is
designed for a specific monitoring purpose. Caliper is not a direct instrument
5) What are sources of error in reading a caliper?
a) Scale misreading (Parallax effect).
b) Alignment error.
c) Excessive measuring force cause the jaw to tilt.
d) Thermal expansion caused by the difference in temperature between the
work piece and the caliper.
e) Inside jaw offset.
6) What could happen if the locking screw is not used in measuring ?
This will move the vernier scale causing change in readings.
7) Is the reading taken for an inside measurement is final?
No we have to add the dimension of the two inside jaws.
8) Is the vernier line standard or end standard ?
End standard.
9) Advantages of caliper over a micrometer.
1) Easy to use.
2) Quick and simple to operate.
3) Can measure many parameter in the same device.
Micrometer:
1) Draw a depth gauge micrometer and put all the parts.
2) how many screw threads are in each micrometer?
The spindle of an ordinary metric micrometer has 2 threads per millimeter.
3) Does the external micrometer obeys the abbe’s principle ?How?
Yes , micrometer conforms to abbe's principle because the graduations are
located along the same axis as the measurement.
4) What is the total length approached by moving the barrel when it rotates
a complete revolution?
one complete revolution moves the spindle through a distance of 0.5
millimeter
5) over tightening will damage the micrometer. Explain
over tightening will make the threads overlap which cause error in reading
and of course damages the micrometers threads.
6) the accuracy of the micrometer depends on the accuracy of the screw
thread, Explain?
Because accuracy depends on the no. of division of the thimble scale that
rotates on screws which have a pitch. So different pitch gives different
accuracy for the micrometer.
7) What are sources of error in reading a micrometer?
Human errors:
Fast observing of the reading.
Observing the readings from an angle and not straight .
Systematic error:
Misalignment micrometer
8) Is the spindle rotating or non rotating type? Name disadvantages of
rotating type?
The spindle is from a rotating type and one of the main disadvantages of
rotating spindle is that it exerts a twisting action on the working piece.