Mechanical Measurement

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.

5

HEIGHT GAUGE

6

DEPTH GAUGE

7

A-6

8

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.

9

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.

10

MEASUREMENT OF NOISE

• FOR THE TRAFFIC NOISE MEASUREMENT AND ENGINE NOISE MEASUREMENT, THIS METER IS USED.

11

12

13

Using automotive stethoscope to locate the source of engine noise.

14

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

16

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.

19

20

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.

24

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.

27

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.

31

MEASUREMENT OF ACCELERATION

• Successive differentiation (LVDT, PIEZOELECTRIC, STRAIN GAUGE)

• Successive integration( ACCELERATION TRANSDUCER)

• Integrator using op-amp.• Differentiator using op-amp.