PRESENTATION ON

COMPARATORS

GUIDED BY:- PROF. NAMAN DAVE

MECHANICAL MEASUREMENT AND METROLOGY

SUBMITTED BY:HIMANSHI GUPTA(140120119057) / ME / A2PRACHI SHARMA(140120119216) / ME / A2

(2141901)

GANDHINAGAR INSTITUTE OF TECHNOLOGY

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

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.

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.

Uses Of Comparators

• Comparators can be used as:1. Laboratory Standards2. Working Gauges3. Final Inspection Gauges4. Receiving Inspection Gauges5. For Checking Newly Purchased Gauges

Characteristics1. Robust Design and Construction2. Linear Characteristics of Scale3. High Magnification4. Quick in Results5. Versatility6. Minimum Wear of Contact Point7. Free from oscillations and back lash8. Quick Insertion of Work piece9. Adjustable table10.Compensation from Temperature Effects11. Means to Prevent Damage

Classification1. Mechanical comparators• Dial Indicator • Reed Type comparator• Sigma Comparator• Johansson Mikrokator2. Mechanical Optical Comparators• Optical Lever• Zeiss Optimeter• Zeiss Ultra Optimeter• Zeiss Optotest Comparators3. Electrical and Electronics Comparators4. Pneumatic Comparators

5) Fluid Displacement Comparators6) Projection Comparators7) Multi check Comparators8) Automatic Gauging9) Electro Mechanical Comparators10) High Sensitive Calibration Comparators• Brookes Level Comparators• Eden-Rolt Millionth Comparators

Classification

• 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

1. Dial Indicator

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 limits2. For determining errors in geometrical forms3. For testing alignment, roundness and parallelism

of work piece4. For quality control and inspection work

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

2.Johannson mikrokator

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 Block2. B- Floating Block3. C- Reeds

4. Sigma Comparator

• Principle Works on leverage

principle in which high magnification is obtained

4. Sigma Comparator

Mechanical Comparators• Advantages1. Do not require any external source of energy2. Cheaper and portable3. Robust construction and compact design4. The simple linear scales are easy to read5. 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 scale2. 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 less4. The instrument may become sensitive to vibration due to high

inertia

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.

• Advantages:-1. Less friction and inertia effect and higher accuracy2. High magnification3. Enables readings to be taken irrespective of room lighting

conditions4. High range and no parallax• Disadvantages:-1. Requires light source2. Large and expensive3. Inconvenient for continuous use4. Instrument setting may drift

Mechanical-Optical Comparators

Electrical Comparator

• Principle:-Operation

depends on an AC Wheatstone bridge circuit incorporating a galvanometer.

Electrical Comparator

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.

Pneumatic Comparators

• Advantages:-1. Very high magnification2. Less friction, wear and inertia3. Less measuring pressure4. Determines ovality and taperness of circular bores• Disadvantages:-1. Scale is generally not uniform2. Requires compressor and accurate pressure regulator3. Non portable4. Less sensitivity

Pneumatic Comparators

Thank You