COMPARATORS Introduction Comparator is an instrument used for

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 03/03/2012 Lecture # 21 & 22 1

COMPARATORS Essential Parts of Comparators: 1. Fixed surface from which all measurements are taken 2. 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 face Arrangement 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 03/03/2012 Lecture # 21 & 22 2

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 03/03/2012 Lecture # 21 & 22 3

COMPARATORS Desirable Features of a Comparator: 1. It should at least be able to record variations of 0. 0025 mm 2. Recording scale should be linear 3. Maximum rigidity 4. Maximum compensation of temperature effect 5. Neither lag nor backlash in the movement of the plunger & recording mechanism 6. Indicator should be constant in its return to zero 7. Measurement pressure should be low & constant 8. Instrument should be capable of a wide measuring range 03/03/2012 Lecture # 21 & 22 4

COMPARATORS Uses of Comparators: 1. To inspect newly purchased gauges 2. In mass production, where components are to be checked at a very fast rate 3. As laboratory standards from which working or inspection gauges are set & correlated 4. As working, to prevent work spoilage & to maintain required tolerance at all important stages of manufacture 03/03/2012 Lecture # 21 & 22 5

COMPARATORS Types of Comparators: Most common commercially available comparators can be classified into the following types: 1. Mechanical comparators 2. Optical comparators 3. Electrical & Electronic comparators 4. Fluid displacement comparators 5. Pneumatic comparators 03/03/2012 Lecture # 21 & 22 6

COMPARATORS Types of Comparators: A combination of magnifying principles has lead to the development of a few more types of comparators, which are: 6. 7. 8. Mechanical-Optical comparators Electro-mechanical comparators 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 03/03/2012 Lecture # 21 & 22 7

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. 03/03/2012 Lecture # 21 & 22 8

MECHANICAL COMPARATOR • Some of the comparator which belong to this class are: 1. Dial indicator 2. Reed type comparator 3. Sigma Comparator 4. Johnson Mikrokrator 5. Eden Rolt Millionth Comparator 03/03/2012 Lecture # 21 & 22 9

MECHANICAL COMPARATOR 1. Dial Indicator: 03/03/2012 Lecture # 21 & 22 10

MECHANICAL COMPARATOR 1. Dial Indicator: (different uses) 03/03/2012 Lecture # 21 & 22 11

MECHANICAL COMPARATOR 1. Dial Indicator: (Various Uses) 03/03/2012 Lecture # 21 & 22 12

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) 03/03/2012 Lecture # 21 & 22 13

Practical # 06 Object: To Learn Use of Vernier Height Gauge Aparatus: Vernier Height Gauge Procedure: As demonstrated/written in practical handout Observation: 03/03/2012 Sr# Object Name Lecture # 21 & 22 Size measured 14

Practical # 06 Vernier Height Gauge: 03/03/2012 Lecture # 21 & 22 15

Practical # 06 Vernier Height Gauge: 03/03/2012 Lecture # 21 & 22 16