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