Measurement Standards

Presented by:

CONTENTS

• Introduction

• Measurement

• Measurement standards

• Types of standards

• Line standards

• End standards

• Wavelength standards

• Subdivisions of standards

• Calibration

Measurement is key to research and development.

MEASUREMENT

Introduction

• In 3000BC Royal cubit was defined as the length

of the forearm of the ruling Pharaoh, plus the

breadth of his hand

• In 16th century feet was created

• In 18th century yard was declared by King Henry

• In 19th century Meter was upgraded and wave

lengths of light proved a remarkable stable

standard

MEASUREMENT STANDARDS

• The meaning of "standard" is something that is set

up and established by authorities as a rule for the

measurement of quantity, weight, value quality,

etc.

• A measurement standard (Etalon) is a material

measure, measuring instrument, reference

material or measuring system intend to define,

realize, conserve or reproduce a unit or one or

more value of a quantity to serve as a reference.

MEASUREMENT STANDARDS

• Line and End standard are referred as Measurement standard in industries, which are used as references for calibration purpose.

• In the modern metrological era, digital instruments such as a periodically calibrated digital height gauge are commonly used.

• Light wave standards are used for laboratory purposes only.

a)Line standard

b)End standard

c) Wave length standard

TYPES OF STANDARDS

a) Line standard

Acorrding to line standard the yard or Metre is defined as the distance between inscribed line on a bar of metal under certain conditions of temperature and support.

a) The imperial standard Yardb) International standard Prototype Metre

The imperial standard Yard

It is made of a one-inch square cross section bronze bar(82% copper, 13% tin, 5% zinc) and is 38 inches long. The bar has a 1/2 inch deep hole, which are fitted with a 1/10th inch diameter gold plug. The yard is defined as the distance between two central transverse lines on the plugs when the temperature of the bar is constant at 62 F.

International standard Prototype Metre

The International Bureau of Weights and Measures established the Metre as the linear measuring standard in the year 1875. The Metre is the distance between the centre portions of two lines engraved on the polished surface of a bar made of platinum (90%) iridium (10%) alloy having a unique cross section. This bar is kept at 0C and under normal atmosphere pressure

b) End standard

The need of end standard arises as the use of line standards and their copies was difficult at various places in the workshop.

End standards are used in workshops and general use in precision engineering in standard laboratories.

These are in the form of end bars and slip gauges.

End bar

End bars made of steel having cylindrical cross section of 22.2 mm diameter with face lapped and hardened at the ends are available in sets of various lengths. End bars are usually provided in sets of 9 to 12 pieces in step size of 25 mm up to a length of 1m.

Slip Gauges

They are used in linear measurement in many ways.Slip gauges are rectangular block of hardened and stabilized high grade cast steel or the ceramic compound zirconium oxide.They are available 9mm wide, 30-35mm long cross section.There are different accuracy grades of slip gauges.

• These standards are used for high sensitivity length measurements have to be taken.

• The primary wavelength standard can be a laser standard which has its frequency compared with Cs time, and frequency standard.

• High frequency accuracy, high-frequency stability and high re-producability help in high-accuracy interferometry length measurements.

c) Wave length standard

• The CGPM (Conference Generale das Poids et Mesurs) adopted a definition of the metre in terms of the wavelength.

c) Wave length standard

METER:The meter is defined as the wavelength of a krypton-86 lamp as the length equal to 1,650,763.73 wavelengths in vacuum corresponding to the transition between two energy levels of the atom Krypton-86.

YARD:1 YARD=0.914 METERS

SUBDIVISIONS OF STANDARDS

There are four level of standards used as

references all over the world

1) Primary standard is the one that is kept in

Paris.

2) Secondary standards is kept in the custody

of every country in laboratory.

3) Tertiary standard used in the industry.

4) Working standards is used on the shop

floor.

Calibration

Calibration is a comparison of instrument performance to standards of known accuracy. Calibrations directly link customers' measurement equipment to national and international standards.

The advantages of calibration are accuracy in performing manufacturing operations, reduced inspection, and ensured quality products by reducing errors in measurement.

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