INDIAN INSTITUTE OF TECHNOLOGY, GANDHINGAR CALIBRATION OF VERNIER CALIPER METROLOGY LAB
NAME: ANIL CHEJARA ROLL NO: 9003022 GROUP: 5
IIT-Gandhinagar
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METROLOGY LAB
Table of Content:
1. Objective___________________ Objective______________________________ ______________________ ______________________ ______________________ ____________________3 _________3 2. Equipment__________________ Equipment_____________________________ ______________________ ______________________ ______________________ ___________________ ________ 3 3. Theory _______________________ __________________________________ ______________________ ______________________ ______________________ _________________3 ______3 4. Procedure__________ Procedure_____________________ ______________________ ______________________ ______________________ ______________________ _________________4 ______4 5.Observation_______________________ 5.Observation__________ ______________________ ______________________ ______________________ ______________________ ________________5 ___5 5. Calculations______________________ Calculations________________________________ _______________________ _________________________ _______________________ _____________6 __6 6. Conclusion__________________ Conclusion______________________________ _______________________ ______________________ ______________________ ___________________7 ________7 7. Comment________________ Comment____________________________ _______________________ ______________________ ______________________ ______________________7 ___________7
SIGNATURE Prof. N. RAMAKRISHNAN IIT GANDHINAGAR
IIT-Gandhinagar
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METROLOGY LAB
AIM: To calibrate vernier caplier. EQUIPMENT: Vernier Caliper and box of slip gauges THEORY:
Calibration is done to check c heck precision and accuracy of o f 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).
IIT-Gandhinagar
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METROLOGY LAB
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 retur ned to their case.
PROCEDURE:
IIT-Gandhinagar
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.
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METROLOGY LAB
OBSERVATIONS: 1) Using single slip gauge
Sr.No.
Slip Gauge Reading (mm)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1.45 2.5 3.5 6.5 7 9 12 14 15 17.5 20 21.5 23 24.5 50
Vernier caliper Reading (mm) 1.44 2.46 3.5 6.48 7 8.98 11.98 13.98 14.98 17.48 20 21.48 22.98 24.48 50
2) Using combination of slip gauges
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Sr.No.
Combination used
Gauge Reading (mm)
1 2 3 4 5 6 7 8 9 10
3.5+4+5+5.5 10+15+16 10.5+23.5+24 10+50 15+23.5+24 3+75 50+75 9+50+75 20+24.5+100 50+75+150
18 41 58 60 62.5 78 125 134 144.5 225
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Vernier caliper Reading (mm) 17.96 41.04 57.98 59.98 62.6 77.98 125.08 134.12 144.5 225
METROLOGY LAB
CALCULATIONS: Sr.no.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Standard Reading (mm) 1.45 2.5 3.5 6.5 7 9 12 14 15 17.5 18 20 21.5 23 24.5 41 50 58 60 62.5 78 125 134 144.5 225
Vernier Reading (mm) 1.44 2.46 3.5 6.48 7 8.98 11.98 13.98 14.98 17.48 17.96 20 21.48 22.98 24.48 41.04 50 57.98 59.98 62.6 77.98 125.08 134.12 144.5 225
Error (mm) 0.01 0.04 0 0.02 0 0.02 0.02 0.02 0.02 0.02 0.04 0 0.02 0.02 0.02 -0.04 0 0.02 0.02 -0.1 0.02 -0.08 -0.12 0 0
%Error
0.69 1.6 0 0.308 0 0.222 0.167 0.143 0.133 0.114 0.222 0 0.093 0.087 0.082 0.098 0 0.034 0.033 0.16 0.026 0.064 0.09 0 0
error vs standard reading 0.05 0 0
)
50
100
150
200
2 50
m -0.05 m ( r o -0.1 o r e
-0.15
standard reading(mm)
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METROLOGY LAB
% error vs standard reading 1.8 1.6 1.4 1.2 r 1 o r r 0.8 e % 0.6 0.4 0.2 0 -0.2 0
50
100
150
200
250
standard reading(mm)
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:
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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.
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