Mechanical Measurement and Metrology

1. PRESENTATION
ON
COMPARATORS
GUIDED BY:- PROF. NAMAN DAVE
MECHANICAL MEASUREMENT AND METROLOGY
SUBMITTED BY:
HIMANSHI GUPTA(140120119057) / ME / A2
PRACHI SHARMA(140120119216) / ME / A2
(2141901)
GA N D H IN A GA R IN STITU TE OF
TEC H N OLOGY

2. Contents
• Introduction
• Basic Principle
• Uses
• Characteristics
• Classification
• Mechanical Comparators And Its Types
• Mechanical-Optical Comparators
• Electrical Comparators
• Pneumatic Comparators

3. Introduction
• Comparator is a precision instrument
• Employed to compare the dimension of given
component with given standard
• Employed to find out, by how much the
dimensions of the given component differ from
that of a known datum.

4. Basic Principle
• Initially, the comparator is adjusted to zero on its dial with a standard
job in position.
• The reading H1is taken with the help of a plunger.
• Then the standard job is replaced by the work-piece to be checked and
the reading H2 is taken.
• If H1and H2 are different, then the change in the dimension will be
shown on the dial of the comparator.

5. Uses Of Comparators
• Comparators can be used as:
1. Laboratory Standards
2. Working Gauges
3. Final Inspection Gauges
4. Receiving Inspection Gauges
5. For Checking Newly Purchased Gauges

6. Characteristics
1. Robust Design and Construction
2. Linear Characteristics of Scale
3. High Magnification
4. Quick in Results
5. Versatility
6. Minimum Wear of Contact Point
7. Free from oscillations and back lash
8. Quick Insertion of Work piece
9. Adjustable table
10.Compensation from Temperature Effects
11.Means to Prevent Damage

7. Classification
1. Mechanical comparators
• Dial Indicator
• Reed Type comparator
• Sigma Comparator
• Johansson Mikrokator
2. Mechanical Optical Comparators
• Optical Lever
• Zeiss Optimeter
• Zeiss Ultra Optimeter
• Zeiss Optotest Comparators
3. Electrical and Electronics Comparators
4. Pneumatic Comparators

8. 5) Fluid Displacement Comparators
6) Projection Comparators
7) Multi check Comparators
8) Automatic Gauging
9) Electro Mechanical Comparators
10) High Sensitive Calibration Comparators
• Brookes Level Comparators
• Eden-Rolt Millionth Comparators
Classification

9. • Self controlled and no power or any other form of
energy is required
• It employs mechanical means for magnifying the
small movement of the measuring stylus
• The movement is due to the difference between
the standard and the actual dimension being
checked
Mechanical Comparators

10. 1. Dial Indicator

11. 1. Dial Indicator
• Amplifies the length or displacement and translate
it into rotational motion of pointer over circular
scale
• Applications:-
1. To compare two heights or distance between
narrow limits
2. For determining errors in geometrical forms
3. For testing alignment, roundness and parallelism
of work piece
4. For quality control and inspection work

12. 2.Johannson mikrokator
• Principle
 When a tension is applied
to the twisted strip, it
causes the strip to untwist
resulting in rotation of
pointer which is attached
at centre of the twisted
strip

13. 2.Johannson mikrokator

14. 3.Reed Type Mechanical Comparator
•A reed type comparator uses the
frictionless reed mechanism for
magnifying small motions of
spindle
•In the following figure:
1. A - Fixed Block
2. B- Floating Block
3. C- Reeds

15. 4. Sigma Comparator
• Principle
 Works on leverage
principle in which high
magnification is
obtained

16. 4. Sigma Comparator

17. Mechanical Comparators
• Advantages
1. Do not require any external source of energy
2. Cheaper and portable
3. Robust construction and compact design
4. The simple linear scales are easy to read
5. Unaffected by variations due to external source of energy such air,
electricity etc
• Disadvantages:
1. Range is limited as the pointer moves over a fixed scale
2. Pointer scale system used can cause parallax error.
3. There are number of moving parts which create problems due to
friction, and ultimately the accuracy is less
4. The instrument may become sensitive to vibration due to high
inertia

18. Mechanical-Optical Comparators
•Principle:
It works based on
fundamental optical law
as the edge of the
shadow is projected on a
curved graduated scale
to indicate the
comparison
measurement.

19. • Advantages:-
1. Less friction and inertia effect and higher accuracy
2. High magnification
3. Enables readings to be taken irrespective of room lighting
conditions
4. High range and no parallax
• Disadvantages:-
1. Requires light source
2. Large and expensive
3. Inconvenient for continuous use
4. Instrument setting may drift
Mechanical-Optical Comparators

20. Electrical Comparator
• Principle:-
Operation
depends on an AC
Wheatstone
bridge circuit
incorporating a
galvanometer.

21. Electrical Comparator

22. Pneumatic Comparators
• Principle:-
 The change in pressure between nozzle and work
piece is utilized to measure the deviation of the
dimension being measured from the standard
dimension.

23. Pneumatic Comparators

24. • Advantages:-
1. Very high magnification
2. Less friction, wear and inertia
3. Less measuring pressure
4. Determines ovality and taperness of circular bores
• Disadvantages:-
1. Scale is generally not uniform
2. Requires compressor and accurate pressure regulator
3. Non portable
4. Less sensitivity
Pneumatic Comparators

25. Thank You 