Use of Comparators in Mass production works

Comparator
A comparator is a device, which is not a measuring device, but it is a comparing device. In general the comparators compares the objects with reference to a standard master piece. Comparators finds their application is all type of production works as these require very less skill and reduces the time of inspection as it requires just a comparison of the values or the dimensions of the product produced. Comparators are in general are classified in to many categories based on the type of principle applied for obtaining the readings.
1) Mechanical comparator
2) Mechanical-optical comparator
3) Electrical and electronic comparator
4) Pneumatic comparator
5) Fluid displacement comparator
6) Projection comparators
7) Multi check comparators
8) Automatic gauging comparators
Irrespective of the type to which the comparators belongs it should fulfill some of the basic characteristics

Characteristics of Comparators

1) A comparator should posses a robust design and construction so as it should give an accurate value even at the worst possible conditions at available at the level of ordinary usage.
2) When a magnification system is used for obtaining deadbeat readings care should be taken to eliminate the backlash, wear resistance in the mechanical components and make the inertia gets reduced to the minimum possible extent.
3) A large range of temperature should be taken in to condition. The comparators should sustain all the temperatures, which are possible in the global context.
4) A scale with linear and having a straight line characteristic should be employed
5) The indicator should be constant when it retains its position back to zero
6) Irrespective of its sensitiveness a comparator should with stand a reasonable ill usage or wrong handling when the user does not cause a permanent harm.
7) The comparator should be prepared in such a way that it can be employed for a wide range of applications
8) The measuring pressure should be always constant and should be low.

Uses of comparators

Comparators find their usage in many areas of production irrespective of the job being produced.
1) They find usage in mass production where the components are required to be checked at a faster rate.
2) These are also used as laboratory standards and are used for making the working or inspection gauges correlated and set
3) Comparators are used for inspecting newly purchased gauges
4) These can also used as some special attachments to the production machines such that the work being done can be regularly checked so as to reduce the wastage of the work due to errors
5) These finds usage in assembly sections where more than three parts are to be assembled

Advantages and disadvantages of various types of comparators

Mechanical comparators

Advantages

1) Cheaper than all the other type of comparators
2) Does not require any external source of power or air supply
3) These comparators use a linear scale that can be easily understood.
4) Usually these comparators are robust and compact but are very easy to handle
5) These are small in size and can are portable from one place to other very easily without much difficulty

Disadvantages

1) Contains more number of moving parts so there develops friction which in turn reduces the accuracy
2) Slackness in the moving parts reduces accuracy very drastically
3) These have more inertia so the instrument is prone to vibrational effects
4) Limited range of the instrument is another drawback as the pointer moves over a fixed scale
5) Parallax error may also arise when proper scale is used

Optical comparators

Advantages

1) Less number of moving parts hence more accuracy
2) High range and no parallax error
3) High magnification possible
4) Weight less optical lever

Disadvantages

1) Due to high magnification the heat produced from the lamp may cause drift
2) Electrical supply is necessary
3) Large in size and expensive
4) Dark room is required to take the readings
5) These cannot be used continuously as the scale is viewed through a microscope

Electrical comparators

Advantages

1) Small number of moving parts
2) High range of usage
3) Not sensitive to vibrations
4) As a A.C source is used for the working of comparator the cyclic vibration generated by A.C source reduces the sliding friction
5) Measuring unit can be made very small

Disadvantages

1) Requires external power supply
2) Calibration may be altered due to heating elements used
3) Expensive

pneumatic comparators

Advantages

1) No wear
2) High accuracy
3) Less friction and less inertia
4) Indicating instrument can be remote from the measuring instrument
5) High magnification is possible
6) Very small diameter holes can be easily measured even when the length is very large
7) Best instrument for determining the ovality and taperness of the circular bores

Disadvantages

1) many instruments are used in addition to the normal set up
2) scale is not uniform
3) when the indicating device is kept in a glass tube a high level of magnification is required so as to minimize meniscus errors
4) machine is not easily portable as it has large equipment
5) different gauging heads are required