comparators and its types

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Comparators:

Comparators Comparator is a precision Instrument used to compare dimension of a given component with a working standard.

Principle of Operation :

Principle of Operation Comparator is first adjusted to zero on dial with gauge block in position. The gauge block will have the dimension of work piece. Next, Work piece is placed in the comparator, gives the difference in dimension in relation to gauge block. Dimension may be less than , greater than or equal to the standard dimension Change in dimension will be shown in the dial of the comparator.

Classification:

Classification Mechanical Comparator. Mechanical- Optical Comparator. Electrical- Electronic Comparator. Pneumatic Comparator.

Mechanical Comparator:

Mechanical Comparator Dial gauge The Johansson Mikrokator Reed type Mechanical Comparator Sigma Comparator

Dial Indicator:

Dial Indicator

Johansson Mikrokator:

Johansson Mikrokator

WORKING:

WORKING The instrument is initially calibrated to the standard , and the zero is set to this value. Then , the test specimen are placed on the measuring table and are slid below the plunger of the instrument. Any difference in the measured dimension of the specimen will result in either the lowering or rising of the plunger. The lowering or rising of plunger will make the bell crank lever to move in forward or backward direction, and in turn, will twist or untwist the metallic strip.

Reed type Comparator:

Reed type Comparator

Sigma Comparator:

Sigma Comparator

Advantages of Mechanical Comparator:

Advantages of Mechanical Comparator Less costly as compared to other devices. Instrument do not require any external agency like air or electricity. Usually mechanical Comparators have linear scales. They are compact in design They are easily portable

Disadvantages of Mechanical Comparators:

Disadvantages of Mechanical Comparators Less accuracy, due to more moving parts, friction reduces accuracy. They are sensitive to vibrations. Range of instrument is limited, as the pointer moves over a fixed scale Any dimensional faults in the mechanical devices will be magnified.

Mechanical-Optical Comparator:

Mechanical-Optical Comparator

Advantages of optical comparator:

Advantages of optical comparator Less moving parts, so high accuracy. High magnification is possible. Optical lever is weight less.

Disadvantages of optical Comparator:

Disadvantages of optical Comparator Depends on availability of external power supply. Apparatus is usually expensive. When scale is projected on screen , instrument is to be used in dark room. Inconvienient for continuous use, because scale is viewed through eye piece.

Pneumatic Comparator:

Pneumatic Comparator

Advantages of pneumatic comparator:

Advantages of pneumatic comparator High degree of magnification is possible. Less number of moving parts. Gauging member does not come in contact with part to be measured. Hence no wear and tear will occur. Measuring pressure is less, so jet of air helps in cleaning the dust.

Disadvantages of pneumatic Comparator:

Disadvantages of pneumatic Comparator Gives low speed of response when compared to others. Require auxiliary equipment like pressure regulator. Scale is generally non uniform. Apparatus is not easily portable.

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