Standards of Measurement

Standards of measurement, Historical developments of standards of measurements, material length standard, international yard, international prototype meter, Lightwave or optical length standards, primary standards, secondary standards, tertiary standards, working standards, line standards, end standards,

1. Standards of Measurement Prepared by: Ratnadeepsinh m jadeja 3/9/2019 Ratnadeepsinh M Jadeja

2. Standards ? For every kind of quantity to be measured there must be a unit to express the result of measurement and a standard. A standard is defined as something that is set up and established by authority as a rule for the measurement of quantity, weight , value etc. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

3. Historical Developments Measurement is of considerable importance in engineering and is required at all stages of manufacture. Any system of measurement must be related to a known standard otherwise the measurement has no meaning. Hence all the measurements of length are fundamentally comparisons with a standard length. Prepared by: Ratnadeepsinh M Jadeja The earliest record length standard was the Egyptian cubit which was the distance from the elbow to tip of the outstretched middle finger. 3/9/2019 Ratnadeepsinh M Jadeja

4. Historical Developments The English rod was defined as the total length of the left feet of the first sixteen men to come out of church on Sunday morning. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

5. Historical Developments The early yard was defined as the distance from the tip of the nose to the end of the thimble when the arm was overstretched. An inch of 1325 was the length over three barely corns. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

6. Historical Developments Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

7. Historical Developments As early as 1805 Maudslay had constructed a micrometer which was used in his workshop to settle any dispute regarding the accuracy of measurement. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

8. Material Length Standards Imperial Standard yard is a bronze (82% copper, 13% tin, 5% zinc) bar of 1 inch × 1 inch square section and 38 inches long. A round recess, one inch away from the two ends is cut at both ends up to the central plan of the bar. Prepared by: Ratnadeepsinh M Jadeja A gold plug 1/10 inch dia. Is inserted into these holes so that lines are in neutral plane. Yard is then defined as the distance between two central transverse lines of the plug at 62° F. 3/9/2019 Ratnadeepsinh M Jadeja

9. Material Length Standards American standard yard was defined at a temperature at 68° F and very slightly longer than the imperial standard yard. Bronze alloy was not stable and continuously shrunk at the rate of one-millionth of an inch for the past 50 years 1922 – relationship between yard and meter by specifying it as legal size. 1 yard = 0.91439841 meter Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

10. International Yard Increasing demand for accurate, internationally interchangeable engineering devices and the problems arising from the varying ratio between the imperial standard yard, and American standard yard and the prototype meter were resolved in 1960 Prepared by: Ratnadeepsinh M Jadeja 1 International yard = 0.9144 meter 1 inch = 25.4 mm 3/9/2019 Ratnadeepsinh M Jadeja

11. International Prototype Metre When the metric system of weight and measurement was originally founded, the metre was intended to be one ten millionth part of the polar quadrant of the Earth passing through Paris. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

12. International Prototype Metre Measurement of the arc between Dunkirk and Barcelona were completed in 1798 and the following year platinum length bar corresponding to one meter was deposited. This served as metric length standard until 1875 when it was replaced by platinum-iridium, international prototype metre . The length of the metre is defined as the straight line distance, at 0° between the centre portions of pure platinum-iridium alloy (10% iridium) of 102 cm total length and having a cross section. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

13. International Prototype Metre Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

14. Light Wave (Optical) Length standard In order to define a standard length in this way it was necessary to find a suitable light source from which a given radiation could be readily selected, the wavelength of the selected radiation then being measured and used as the basic unit of length. Eleventh General Conference of Weights and Measures held in Paris in 1960 defined the metre as equal to 1650763.73 wave lengths of the red orange radiation of krypton isotope 86 gas. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

15. Light Wave (Optical) Length standard It made primary unit accessible to any laboratory, and reduced its uncertainty by a factor of 50. Let x = the number of wavelengths of Kr-86 in the meter, then 1 mm = 1 inch = 1 yard =   Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

16. Advantages of Light Standard It does not change length. If destroyed it can easily be replaced. Identical copies can be kept in all standard rooms and physical laboratories. It can be used for making comparative measurements of a much higher accuracy than was possible with the older material standards. It will give a unit of length which could be produced consistently at any time in all countries. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

17. Metre as of today Since seventies, it was foreseen that a definition based on the speed of light would soon be technically feasible and practically advantageous. On the 20 th October 1983 the 17 th General Conference of Weights and Measures agreed to a fundamental change in the definition of the metre . Metre is now defined as the length of the path travelled by light in vacuum in 1/299792458 second . Prepared by: Ratnadeepsinh M Jadeja Iodine Stabilized Helium-neon Laser 3/9/2019 Ratnadeepsinh M Jadeja

18. Subdivisions of Standards The international yard and international prototype metre , described previously, are considered to be perfect or master standards and obviously can not be used for general purposes. For practical purposes there is a hierarchy of working standards. For example, in most firms inspection gauge slip gauges would be used to check and measure work produced using workshop grade slip gauges, micrometers, verniers , rules etc. The standards are subdivided into following four grades. Primary standards Secondary standards Tertiary standards Working standards Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

19. Primary Standards For precise definition of the unit it is essential that there shall be one, and only one material standard. This is called primary standard and is preserved under the most careful conditions, used only at rate intervals and then solely for comparison with secondary standards. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

20. Secondary Standards They are made as nearly as possible to the primary standard with which they are compared at intervals, and records of their deviation from it. These standards are distributed to a number of places for a safe custody and used in their turn for occasional comparison for tertiary standards. Material for secondary standards Invar an alloy of nickel and steel Fused silica Elinvar -an alloy of nickel and chromium. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

21. Tertiary Standards These are the first standards to be used for reference purpose in laboratories and workshops. The primary and secondary types exist only as ultimate controls, for reference at rate intervals. Tertiary standards should also be maintained as a reference for comparison at intervals with working standards. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

22. Working Standards “Working” or secondary line standards are necessary for use in scientific laboratories and similar institutions. They are derived from the fundamental standards. Line standard bars are usually made from an H-cross-sectional form. Line Standards End Standards Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

23. Line and End Measurement Distances have sometimes to be measured between two lines and sometimes between two surfaces, or a combination of line and surfaces. When the length being measured is expressed as the distance between two lines, this referred as line measurement . When the length being measured is expressed as the distance between two surfaces, this is referred as end measurement. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

24. Line and End Measurement Prepared by: Ratnadeepsinh M Jadeja Primary standards are Line standards. Practically the workshop standards are end standards derived from the Line Standards. 1 meter calibrated composite line standard 950 mm 50 mm 50 mm 3/9/2019 Ratnadeepsinh M Jadeja

25. Characteristics of Line Standards Scale can be accurately engraved but it is difficult to take full advantage of this accuracy. Quick and easy to use over a wide range since only one is required. The scale markings are not subjected to wear although significant wear on leading end leads to “ undersizing ” A scale does not possess a built in datum which would allow easy scale alignment with the axis of measurement, this again leads to undersizing . Scales are subjected to the parallax effect, a source of both positive and negative reading errors. Scales are not convenient for close tolerance length measurement except in conjunction of microscopes. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

26. Characteristics of End Standards End standards are highly accurate and are well-suited to measurements of close tolerance. They are time consuming in use and prove only one dimension at a time. Dimensional tolerance as small as 0.0005 mm can be obtained. They are subjected to wear on their measuring faces. Groups of blocks are wrung together to provide a given size, faulty wringing leads to damage. End standards have a built in datum because their measuring faces are flat and parallel. They are not subjected to the parallax effect as their use depends on “feel” Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

27. Classification of Standards & Traceability In order to maintain accuracy and interchangeability in the items manufactured by various industries in the country, it is essential that the standards of units and measurements followed by them must be traceable to a single source i.e., National Standards of the Country . Clearly, there is degradation of accuracy in passing from the defining standards to the standard in use. All the industrial standardization and industrial product certifications are governed by the Bureau of Indian Standards, the national standards organization of India while standards for other areas (like agricultural products) are developed and managed by other governmental agencies. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

28. Classification of Standards & Traceability Application of precise measurement has increased to such an extent that it is not practicable for a single national laboratory to perform directly all the calibrations and standardizations required by a large country. Therefore, process of traceability technique needs to be followed in stages. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja

29. Certification Marks in India Agmark for all agricultural products BIS hallmark ( BIS hallmark ) certifies the purity of gold jewelry. FPO mark . A mandatory mark for all processed fruit products in India. Geographical Indications marks , defined under the WTO Agreement on Trade-Related Aspects of Intellectual Property Rights ( TRIPS ) India Organic certification mark for organically farmed food products National Standards for Organic Products. SI mark . For industrial product. Non Polluting Vehicle mark on motor vehicles certifying conformity to the Bharat Stage emission standards . Toxicity label is mandatory on the containers of pesticides sold in India. Prepared by: Ratnadeepsinh M Jadeja 3/9/2019 Ratnadeepsinh M Jadeja