calibration of vernier capilier

IIT-Gandhinagar METROLOGY LAB

INDIAN INSTITUTE OF TECHNOLOGY, GANDHINGAR

CALIBRATION OF VERNIER CALIPER

METROLOGY LAB

NAME: ANIL CHEJARA

ROLL NO: 9003022

GROUP: 5


Table of Content:

1. Objective________________________________________________________________________3

2. Equipment______________________________________________________________________ 3

3. Theory _________________________________________________________________________3

4. Procedure_______________________________________________________________________4

5.Observation______________________________________________________________________5

5. Calculations______________________________________________________________________6

6. Conclusion_______________________________________________________________________7

7. Comment________________________________________________________________________7

SIGNATURE Prof. N. RAMAKRISHNAN IIT GANDHINAGAR


AIM: To calibrate vernier caplier.

EQUIPMENT: Vernier Caliper and box of slip gauges

THEORY:

Calibration is done to check precision and accuracy of the measuring instrument. If we have references

which are very accurate and well kept under control environment, they can be used to calibrate.

Slip gauge is a precision ground and lapped length measuring standard used as a reference for the

calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers,

and dial indicators.

Vernier caliper is capable of measuring internal and external dimensions and can also be used as a depth

gauge. The Vernier Caliper is a precision instrument that can be used to measure internal and external

distances extremely accurately. The vernier, dial, and digital calipers that give a direct reading of the

distance measured to high accuracy. These calipers comprise a calibrated scale with a fixed jaw, and

another jaw, with a pointer, that slides along the scale. Its least count is 0.1 /0.2 mm

The vernier scales may include metric measurements on the lower part of the scale and inch

measurements on the upper, or vice versa, in countries that use inches. Vernier calipers commonly used in

industry provide a precision to 0.01 mm (10 micrometres), or one thousandth of an inch. They are

available in sizes that can measure up to 1,829 mm (72 in).


BOX OF SLIP GAUGES:

Slip gauge is a precision ground and lapped length measuring standard. They are used as a

reference for the calibration of measuring equipment used in machine shops, such

as micrometers, sine bars, callipers and dial indicators. Gauge blocks are the main means of

length standardization used by industry.

They are the most accurate standards of length available for use in workshops. The accuracy

and finish is so high that two or more slip gauges may be wrung together. When correctly

cleaned and wrung together, the individual slip gauges adhere to each other by molecular

attraction and if left like this for too long, a partial cold weld will take place. If this is allowed

to occur, the gauging surface will be irreparably after use, the gauges should be separated

carefully by sliding them apart. They should then be cleaned, smeared with oil or petroleum

jelly (Vaseline) and returned to their case.

PROCEDURE:

Check the zero error of the vernier callipers.

Take the slip gauges from the box of different sizes and measure them using the

vernier callipers.

Compare the measured value with the given value of the gauges.

After that, combination procedure, we keep two mirrored surfaces at 90 degrees and

turn so that they stick and their final length will be sum of individual lengths.

Now measure the combined length using the vernier caliper and find out the error.

Take care that the gauges are attached properly. Inability to do that would lead to errors.


OBSERVATIONS:

1) Using single slip gauge

Sr.No. Slip Gauge Reading (mm)

Vernier caliper Reading

(mm)

1 1.45 1.44

2 2.5 2.46

3 3.5 3.5

4 6.5 6.48

5 7 7

6 9 8.98

7 12 11.98

8 14 13.98

9 15 14.98

10 17.5 17.48

11 20 20

12 21.5 21.48

13 23 22.98

14 24.5 24.48

15 50 50

2) Using combination of slip gauges

Sr.No. Combination used Gauge Reading (mm)

Vernier caliper Reading

(mm)

1 3.5+4+5+5.5 18 17.96

2 10+15+16 41 41.04

3 10.5+23.5+24 58 57.98

4 10+50 60 59.98

5 15+23.5+24 62.5 62.6

6 3+75 78 77.98

7 50+75 125 125.08

8 9+50+75 134 134.12

9 20+24.5+100 144.5 144.5

10 50+75+150 225 225


CALCULATIONS:

Sr.no. Standard Reading (mm)

Vernier Reading (mm)

Error (mm)

%Error

1 1.45 1.44 0.01 0.69

2 2.5 2.46 0.04 1.6

3 3.5 3.5 0 0

4 6.5 6.48 0.02 0.308

5 7 7 0 0

6 9 8.98 0.02 0.222

7 12 11.98 0.02 0.167

8 14 13.98 0.02 0.143

9 15 14.98 0.02 0.133

10 17.5 17.48 0.02 0.114

11 18 17.96 0.04 0.222

12 20 20 0 0

13 21.5 21.48 0.02 0.093

14 23 22.98 0.02 0.087

15 24.5 24.48 0.02 0.082

16 41 41.04 -0.04 0.098

17 50 50 0 0

18 58 57.98 0.02 0.034

19 60 59.98 0.02 0.033

20 62.5 62.6 -0.1 0.16

21 78 77.98 0.02 0.026

22 125 125.08 -0.08 0.064

23 134 134.12 -0.12 0.09

24 144.5 144.5 0 0

25 225 225 0 0

-0.15

-0.1

-0.05

0

0.05

0 50 100 150 200 250

ero

or(

mm

)

standard reading(mm)

error vs standard reading


CONCULSION:

The vernier caliper used is precise and very accurate as seeing errors during

calibration.

The error in increases as we combine the blocks, it is because of loose contact.

The error in combination of gauges is the addition of caliberation error and air gap.

For small reading human error can cause to very high error which is misleading.

COMMENTS:

Make sure that slip gauges mirror finish side is pure and clean otherwise it will cause

error.

Human error can affect the results very much for small gauges.

There can be thermal expansion so we need o make sure appropriate environment of

gauges.

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 50 100 150 200 250

% e

rro

r

standard reading(mm)

% error vs standard reading

calibration of vernier capilier

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