Mechanical Measurement and Metrology - Dec 2014

Mechanical Engineering (Semester 4)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Define metrology. what are the objectives of metrology.(5 marks) 1 (b) Explain "Imperial standard yard" and "International prototype meter", with neat sketches.(10 marks) 1 (c) A calibrated meter end bar has an actual length of 1000.0002 mm. It is used in calibration of two bars A and B, each having a basic length of 500 mm. When compared with the meter bar L_A+ L_B was found to be shorter by 0.0003 mm. In comparing A and B, it was found thatA was 0.0004 mm longer than B. Find the actual length of A and B.(5 marks) 2 (a) Differentiate : i) unilateral and bilateral tolerances ii) clearance fit and interference fit.(6 marks) 2 (b) Determine the dimensions of shaft and hole for a fit 30 H⊂7f ⊂ 8. The given data are: $$ i=0.45 \sqrt[3]{D}+0.001D $$ microns. Fundamental deviation for f shaft is -5.5D ⊃ 0.41 at microns, 30 mm falls in the diameter step of 18 and 30. Tolerance grade for IT⊂ 7 and IT⊂8 are 16i and 25i respectively. Also design plug gauge to check the above hole. Take wear allowance as 10% of the gauge tolerance.(10 marks) 2 (c) Explain : i) Shaft basis system ii)Hole basis system.(4 marks) 3 (a) With a neat sketch, explain the construction and working of Johannson Mikrokator comparator(8 marks) 3 (b) Explain with a neat sketch, the working of Solex pneumatic comparator. What are its advantages?(8 marks) 3 (c) Explain the principle of sine bar.(4 marks) 4 (a) With a neat sketch, explain the working principle of an autocollimator.(6 marks) 4 (b) Define "Effective diameter". Explain the 3-wire method of finding the effective diameter of screw threads.(8 marks) 4 (c) Explain with a sketch, how the chordal thickness is measured by using gear tooth vernier calliper.l(6 marks) 5 (a) Define measurement. With a block diagram,explain the generalized measurement system explain the with a suitable example.(8 marks) 5 (b) Define the following terms : i) precision ii) hysteresis iii) sensitivity.(6 marks) 5 (c) Explain the principle of capacitive type electrical transducer. With a skech explain any one type of capacitive transducer.(6 marks) 6 (a) Explain th inherent problems present in mechanical modifying system.(6 marks) 6 (b) With a block diagram, explain the general telemetering system.(6 marks) 6 (c) Explain with neat sketches : i) stylus type oscillograph ii) x - y ? plotter.(8 marks) 7 (a) Sketch and explain the analytical balance (equal arm balance).(8 marks) 7 (c) Describe the working principle of pirani gauge with a sketch.(6 marks) 7(b) Explain how the torque is measured using Prony brake dynamometer. What are its disadvantages?(6 marks) 8 (a) State the laws of thermocouples.(4 marks) 8 (b) Explain the construction and working of optical pyrometer.(8 marks) 8 (c) Define gauge factor. Explain the wheat stone bridge arrangement for stain measurement.(8 marks)