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VTU Mechanical Engineering (Semester 3)
Mechanical Measurement and Metrology
December 2011
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Sketch and explain the following :
Imperial standard yard and international prototype meter.
8 M
1 (b) Compare line and end standards of measurements.
6 M
1 (c) Three 100mm end bars are measured on a level comparator by first wringing them together and comparing with a 300 mm bar. The 300 mm bar has a known error of +40 ?m and the three bars together measure 64 ?m less than the 300 mm bar. Bar A is 18 ?m longer than bar B and 23 ?m longer than bar C. FInd the actual length of each bar.
6 M

2 (a) Explain
(i) Interchangeable manufacturing.
(ii) Selective assembly of machine parts.
5 M
2 (b) Design a general type GO and No GO guages for a hole and shaft pair designated as 450 H8e9 with following details:
(i) 450 mm dia lies in 400-500 mm step.
(ii) The standard tolerance unit i is given by the formula $i=0.45 \ \sqrt{D}+0.001D$ microns (D is in mm).
(iii) IT8=25i, IT9=40i
(iv) The fundamental deviation for an e type shaft=-11D0.41 microns.
Sketch the layout indicating the various tolerance on both holes and shaft and their respective guages.
15 M

3 (a) What is a comparator, what are the needs and characteristics of comparator?
6 M
3 (b) Explain with a neat sketch the working principle of Johansson Mikrokator.
10 M
4 M

4 (a) With a neat sketch, explain the working principle of an auto collimator.
6 M
4 (b) Mention the nominal angles of a standard set of angle guages and indicate how the following angles can be built using angle guages (i) 33°16'12"; (ii)57°34'9"
6 M
4 (c) Define "effective diameter" and "best size wire". Derive an expression to determine the best size wire diameter.
8 M

5 (a) Define measurement with the aid of a block diagram, explain the three stages of a generalized measurement system with suitable example.
10 M
5 (b) Define error in measurement. Give classification of errors.
4 M
5 (c) Define the following :
(i) Accuracy
(ii) Precision
(iii) Sensitivity.
6 M

6 (a) What is a transducer? Differentiate between
(i) Primary and secondary transducers
(ii) Active and passive transducers.
6 M
6 (b) With a neat block diagram, explain the working principle of CRO
10 M
6 (c) State the advantages of electrical signal conditioning elements
4 M

7 (a) Explain with a neat sketch the working principle of McLeod guage.
8 M
7 (b) Explai with a neat sketch the working principle of a Pirani guage.
6 M
7 (c) Explain with suitable diagram the working of hydraulic dynamometer.
6 M

8 (a) What is a thermo couple? State the laws of thermocouple and explain the same.
6 M
8 (b) Derive an expression for guage factor of a strain guage. Why guage factor is at least two for most of the materials?
6 M
8 (c) Explain the working principle of optical pyrometer, with a neat sketch.
8 M

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