CALIBRATION OF VERNIER CALIPER

ME 314: METROLOGY LAB

IIT GANDHINAGAR

Submitted to: Submitted by: Prof. N Ramakrishnan M. Rudra Prasad (09003027)

16th February 2012

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INDEX

OBJECTIVE ....................................................................................................................... 3

INSTRUMENTS USED........................................................................................................ 3

ABOUT VERNIER CALIPER ................................................................................................ 3

PROCEDURE ..................................................................................................................... 3

OBSERVATIONS ............................................................................................................... 4

GRAPHS ............................................................................................................................ 5

CONCLUSIONS ................................................................................................................. 5

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OBJECTIVE: To calibrate a given vernier caliper.

INSTRUMENTS USED: Vernier caliper.

Slip of gauges.

ABOUT VERNIER CALIPER: Vernier caliper is a precision instrument that can be used to measure internal and external

distances extremely accurately.

Here, readings are interpreted from the scale by the user.

Vernier caliper has two scales – main scale and vernier scale as shown in figure below.

Here, Least count of vernier caliper = one main scale division - one vernier scale division. In

our given caliper, Least count = 0.02 mm

Length of given species = Main scale division + ( No. of vernier scale division * Least count)

PROCEDURE: Adjust zero-zero of the vernier caliper.

Set up a standard length using slip gauges. First use individual gauges, and then in

combinations of two or more.

To join two blocks press the shiny surfaces of the two blocks against such that the clocks are

perpendicular to each other. Then, turn the blocks, while pressing them against each other,

such that the profile of one covers the profile of the other.

Measure the same dimension with vernier caliper.

The dimension with slip gauge minus reading on the vernier caliper is the error.

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Repeat the same over a number of parts in the whole range.

OBSERVATIONS: Here, reading given on gauge block as true value and vernier reading as measured value.

Percentage error = ( )

Table 1:

Sr.No Gauge Reading( mm) Vernier reading(mm) % error

1 1.04 1.06 1.92

2 1.1 1.1 0

3 1.3 1.3 0

4 1.4 1.38 1.43

5 1.5 1.5 0

6 4 4.02 0.5

7 5 5 0

8 8 8.02 0.25

9 10 10.02 0.2

10 12.5 12.46 0.32

11 15 14.98 0.13

12 17 16.98 0.12

13 20 19.98 0.1

14 22 22 0

15 25 25 0

16 50 50 0

17 75 75 0

Table 2:

Sr.No Combination of gauges(mm) Gauge reading(mm) Vernier reading(mm) % error

1 1.46+3.50 4.96 4.98 0.40

2 3.00+5.50 8.5 8.5 0

3 6.50+1.14 7.64 7.62 0.26

4 7.50+12 19.5 19.5 0

5 13+13.5+14 40.5 40.5 0

6 6.5+16+24.5 47 47.04 0.08

7 22.5+23.5+13.5+11 70.5 70.5 0

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GRAPHS: Graph 1:

Graph 2:

CONCLUSIONS: The error in the actual gauge values and the vernier readings is less than 2% that may or may

not be negligible; it would depend on the application.

The maximum value of error that occurs is 0.04 mm.

Combinations of gauge blocks may lead to error because of imperfections in the joint

surfaces.

The method adopted is time consuming.

The measurements need to be conducted in a controlled environment to avoid thermal

expansion in the blocks.

The gauge blocks need to be held with care as they have highly finished surfaces, which may

get damaged if the blocks are dropped.

-0.5

0

0.5

1

1.5

2

2.5

0 20 40 60 80

% e

rro

r

Gauge readings(in mm)

Error Vs Gauge reading

-0.1

0

0.1

0.2

0.3

0.4

0.5

0 20 40 60 80

% e

rro

r

Gauge reading( mm)

Error Vs Gauge reading

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