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# Mechanical Measurement

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this note is given bu vidhya nagar to auto students

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### Mechanical Measurement

1. 1. MEASUREMENT<br />WEAR<br />NOISE<br />FUEL CONSUMPTION<br />VIBRATION<br />SPEED<br />ACCELERATION<br />
2. 2. WEAR<br />Wear is the removal of material from the component due to friction or contact with other component.<br />It is necessary to measure the wear of a part because excessive wear may cause the failure of the component and accident may take place.<br />
3. 3. MEASUREMENT OF WEAR<br />The parts having wear is measure by different gauges.<br />Internal wear of a component is measure by depth gauge.<br />External wear of any part can be measure by height gauges.<br />
4. 4. MEASUREMENT OF WEAR<br />The wear between two surfaces which are very close to each other, can be measured by slip gauges as shown in fig.<br />The wear of cylindrical part is measured by bore gauges.<br />
5. 5. HEIGHT GAUGE<br />5<br />
6. 6. DEPTH GAUGE<br />6<br />
7. 7. A-6<br />7<br />
8. 8. MEASUREMENT OF NOISE<br />Noise is any unpleasant sound such as booming, buzzing, whistling.<br />While driving or in idle position if there is some undesirable noise of vehicle component, it should be checked.<br />This noise is due to undesirable contact with other part or vibration.<br />Hence we need to check these noises so we can avoid damage of vehicle component.<br />8<br />
9. 9. MEASUREMENT OF NOISE<br />To check the noise we use “Db Meter”.<br />Decibel Meter is designed for situations where small size, simple operation and high performance are all required.<br />It allows noise levels to be checked quickly and simply with the large LCD digital display showing Sound Level in decibels. <br />9<br />
10. 10. MEASUREMENT OF NOISE<br />FOR THE TRAFFIC NOISE MEASUREMENT AND ENGINE NOISE MEASUREMENT, THIS METER IS USED.<br />10<br />
11. 11. 11<br />
12. 12. 12<br />
13. 13. Using automotive stethoscope to locate the source of engine noise.<br />13<br />
14. 14. ENGINE NOISE<br />Valve and tappet noise.<br />Detonation<br />Connecting-rod noise<br />Piston-pin noise<br />Piston-ring noise<br />Piston slap<br />Crankshaft knock<br />miscellaneous <br />14<br />
15. 15. MEASUREMENT OF FUEL CONSUMPTION<br />There are various mainly two types of measurements<br />Automatic means using electronics.<br />Manually<br />
16. 16. MEASUREMENT OF VIBRATION<br />Vibration meter is used to measure the vibration of particular component.<br />The result is shown in the form of digits in display.<br />Reasons:<br />high tolerance<br />mis-alignment<br />Shocks produced due to sudden change in acceleration.<br />16<br />
17. 17. MEASUREMENTS OF SPEED<br />EDDY CURRENT TACHOMETER<br />TACHOGENERATOR<br />STROBOSCOPE<br />PULSE COUNTER<br />
18. 18. EDDY CURRENT TACHOMETER<br />Shaft whose rpm to be measured is made to drive a U-shaped magnet.<br />This magnet rotates inside the soft-iron casing.<br />An aluminum cup is placed between these two, so field magnet pass through the aluminum.<br />With the relative rotation of magnet with respect to cup, eddy current is generated.<br />
19. 19. 19<br />
20. 20. 20<br />
21. 21. EDDY CURRENT TACHOMETER<br />This eddy current generates its own magnetic field. This magnetic field attracts the field of rotating magnet (earlier field).<br />As a result of it the cup tend to be carried round by a magnetic torque.<br />This torque is proportional to the eddy current, hence in turn proportional to speed of magnet.<br />
22. 22. EDDY CURRENT TACHOMETER<br />The cup is carried by spindle which is free to rotate through part of revolution.<br />The pointer indicates the speed of on the dial of the instrument means dial.<br />Speedometer works on this principle.<br />
23. 23. TACHOGENERATOR<br />Here the armature of the dynamo rotates in the alnico of permanent magnetic field.<br />Its electrical output is the signal of rpm.<br />It is connected to a voltmeter graduated In rpm or km per hour.<br />
24. 24. 24<br />
25. 25. PULSE COUNTER<br />Three main parts are required-<br />A 60 toothed mild steel wheel.<br />A magnetic transducer.<br />A pulse counter.<br />The geared wheel which contains the equally spaced 60 slots is mounted on a shaft.<br />Now here magnetic transducer is a bar magnet and has a coil of a wire wound around it.<br />
26. 26. PULSE COUNTER<br />The ends of the coil are connected to the signal i/p of the pulse generator.<br />As a tooth on a wheel approaches the end of bar magnet, the steel of the tooth provides an easier path for the magnetic field than the gap between the teeth did.<br />Due to this flux density of field increases. Hence generation of voltage occurs. <br />
27. 27. 27<br />
28. 28. PULSE COUNTER<br />So, frequency of AC voltage = no of teeth passing through it<br />With the help of magnetic transducer the ac o/p is collected by the pulse counter ckt (timer ckt ).<br />The rpm of the rotating shaft is then displayed in the form of digital o/p.<br />
29. 29. Stroboscope<br /><ul><li>Principal-Light flashes at the same frequency as that of rotating shaft.
30. 30. Adjusting knob, light characteristics-xenon lamp, short duration, high frequency, marked wheel.</li></ul>Rpm of shaft =no. of flashes /min.<br />
31. 31.
32. 32. MEASUREMENT OF ACCELERATION<br />Successive differentiation (LVDT, PIEZOELECTRIC, STRAIN GAUGE)<br />Successive integration( ACCELERATION TRANSDUCER)<br />Integrator using op-amp.<br />Differentiator using op-amp.<br />31<br />
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