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Experiment No: 3 Date:

Calibration of Measuring Instrument

Aim: To calibrate Measuring Instrument- Dial Indicator.

Apparatus:1) Dial Indicator2) Dial Calibration Tester (Instrumental Error 1 m)

Theory:

Dial indicators, also known as dial gauges and probe indicators, are instrumentsused to accurately measure small linear distances, and are frequently used inindustrial and mechanical processes. They are named so because themeasurement results are displayed in a magnified way by means of a dial.

Dial indicators may be used to check the variation in tolerance during theinspection process of a machined part, measure the deflection of a beam or ringunder laboratory conditions, as well as many other situations where a smallmeasurement needs to be registered or indicated. Dial indicators typicallymeasure ranges from 0.25 mm to 300 mm (0.015 in to 12.0 in), with graduationsof 0.001 mm to 0.01 mm (metric) or 0.00005 in to 0.001 in (imperial).

Applications

To check for run out when fitting a new disc to an automotive disc brake.Run out can rapidly ruin the disc if it exceeds the specified tolerance

(typically 0.05 mm or less).

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In a quality environment to check for consistency and accuracy in themanufacturing process.

On the workshop floor to initially set up or calibrate a machine, prior to aproduction run.

Dial indicators help users measure the distance between two plates, but

the readings given by the tool could be faulty.

Calibration Procedure:

Hold the dial indicator with its spindle set vertically downward, follow the

procedure prescribed below and determine the error of indication with reference

to the dial graduations.

First, displace the spindle upward over the entire measuring range while plotting

errors at every 1/10threvolution of the first two revolutions from zero point. After

first two revolutions to keep the number of readings within practicable limits for

dial gauges with longer travel, only limited number of 1/10threvolution reading

are taken during each revolution of the pointer. Reverse the direction (i.e.

downward displacement) after full range of dial indicator and plot the errors at

the same points measured during upward spindle displacement. Determine

errors from a bidirectional error curve obtained.

Maximum Permissible Error (MPE) of Indication:

Requirement Indication Error MPE (in mm)

Accuracy over aninterval of

Arbitrary 1/10threv. 0.005

Arbitrary 1 rev. 0.010

Arbitrary 2 rev. 0.015

Any larger intervalupto 10 rev.

0.020

Observation Table:

1) For Upward motion of Micrometer Scale:

Divisionof Dial

0 10 20 30 40 50 60 70 80 90

Turn 1 Set

Turn 2

Turn 3

Turn 4

Turn 5

Turn 6

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Turn 7

Turn 8

Turn 9

Turn 10

Minimum Reading =

Maximum Reading =

Range =

2) For Downward motion of Micrometer scale:

Divisionof Dial

0 90 80 70 60 50 40 30 20 10

Turn 10 SetTurn 9

Turn 8

Turn 7

Turn 6

Turn 5

Turn 4

Turn 3

Turn 2

Turn 1

Result Table:

1) Any 1/10threvolution:

Direction Max/Min. RangePermissible

ErrorAccepted/Rejected

UpwardMax.

Min.

DownwardMax.

Min.

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2) Any 1 revolution:

Direction Max/Min. RangePermissible

ErrorAccepted/Rejected

UpwardMax.

Min.

DownwardMax.

Min.

3) Any 2 revolutions:

Direction Max/Min. RangePermissible

ErrorAccepted/Rejected

UpwardMax.

Min.

DownwardMax.

Min.

4) Any Larger interval upto 10 revolutions:

Direction Max/Min. Range

Permissible

Error

Accepted/

Rejected

UpwardMax.

Min.

DownwardMax.

Min.

Conclusion: Hence, we studied calibration of dial indicator using dial calibration

tester.