Lecture # 21 & 22 1

COMPARATORS

Introduction:• Comparator is an instrument used for

comparing the dimensions of a component with a standard of length

• Purpose of a comparator, in general, is to detect & display the small differences b/w the unknown linear dimension & length of the standard

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Lecture # 21 & 22 2

COMPARATORS

Essential Parts of Comparators:1. Fixed surface from which all measurements are taken2. A very sensitive indicator which will show the

movement of a sliding piece usually terminating in an anvil with curved surface

3. Some means of setting the curved faceArrangement of above parts is used to measure the difference b/w the length or diameter of a component & a standard of length, usually made up of slip gauges

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Lecture # 21 & 22 3

COMPARATORS

The Important & essential function of the instrument is to MAGNIFY or AMPLIFY the small input displacements to that it is displayed on an analogue scale

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Lecture # 21 & 22 4

COMPARATORS

Desirable Features of a Comparator:1. It should at least be able to record variations of 0.0025mm2. Recording scale should be linear3. Maximum rigidity4. Maximum compensation of temperature effect5. Neither lag nor backlash in the movement of the plunger

& recording mechanism6. Indicator should be constant in its return to zero7. Measurement pressure should be low & constant8. Instrument should be capable of a wide measuring range

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Lecture # 21 & 22 5

COMPARATORS

Uses of Comparators:1. To inspect newly purchased gauges2. In mass production, where components are to

be checked at a very fast rate3. As laboratory standards from which working or

inspection gauges are set & correlated4. As working, to prevent work spoilage & to

maintain required tolerance at all important stages of manufacture

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Lecture # 21 & 22 6

COMPARATORS

Types of Comparators:Most common commercially available comparators

can be classified into the following types:1. Mechanical comparators2. Optical comparators3. Electrical & Electronic comparators4. Fluid displacement comparators5. Pneumatic comparators

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Lecture # 21 & 22 7

COMPARATORS

Types of Comparators:A combination of magnifying principles has lead to the development of a few more types of comparators, which are:

6. Mechanical-Optical comparators7. Electro-mechanical comparators8. Multi-check comparators

The most interesting & important component on a comparator is the indicating unit, & instruments are made in which the operation for this unit depends on mechanical, electrical or pneumatic principle

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Lecture # 21 & 22 8

MECHANICAL COMPARATOR

• The mechanical comparators utilize mechanical methods of magnifying, the movement of the contact plunger; their manufacture requires a high degree of skill & accuracy.

• The usual magnifications of the mechanisms range from about 250 to 1000.

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Lecture # 21 & 22 9

MECHANICAL COMPARATOR

• Some of the comparator which belong to this class are:

1. Dial indicator2. Reed type comparator3. Sigma Comparator4. Johnson Mikrokrator5. Eden Rolt Millionth Comparator

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Lecture # 21 & 22 10

MECHANICAL COMPARATOR1. Dial Indicator:

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Lecture # 21 & 22 11

MECHANICAL COMPARATOR

1.Dial Indicator: (different uses)

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Lecture # 21 & 22 12

MECHANICAL COMPARATOR

1. Dial Indicator: (Various Uses)

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Lecture # 21 & 22 13

MECHANICAL COMPARATOR

1. Dial Indicator:a. Principal parts: As demonstrated

(more see page# 186)

b. Principal of Operation: As demonstrated(more see page# 186)

c. Dial Indicator Fitted to Pillar stand: As demonstrated (more see page# 187)

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Lecture # 21 & 22 14

Practical # 06

Object: To Learn Use of Vernier Height Gauge

Aparatus: Vernier Height Gauge

Procedure: As demonstrated/written in practical handout

Observation:

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Sr# Object Name Size measured

Lecture # 21 & 22 15

Practical # 06

Vernier Height Gauge:

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Lecture # 21 & 22 16

Practical # 06

Vernier Height Gauge:

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