1.1 The word metrology has a long tradition and is derived from the Greek word for measure. It is well-known saying that the knowledge about anything is complete only when it can be expressed in numbers and something is known about it. Thus for every kind of quantity measured, there must be a unit to […]

Physical Measurement (Metrology)

1.3. Measurement is a complex of operations carried out by means of measuring instruments to determine the numerical value of the size which describes the object of measurement. A physical measurement could be defined as the act of deriving quantitative information about a physical object or action by comparison with a reference. It will be […]

Need of Inspection (Metrology)

1.2. In order to determine the fitness of anything made, man has always used inspection. But industrial inspection is of recent origin and has scientific approach behind it. It came into being because of mass production which involved interchangeability of parts. In old craft, same craftsman used to be producer as well as assembler. Separate […]

Measuring Instruments (Metrology)

1.4. Measuring Instruments are measuring devices that transform the measured quantity or a related quantity into an indication or information. Measuring instruments can either indicate directly the value of the measured quantity or only indicate its equality to a known measure of the same quantity (e.g. equal arm balance, or null detecting galvanometer). They may […]

Selection of Instruments (Metrology)

1.5. The important characteristics to be considered in selection of an instrument are its measur- ing range, accuracy and precision. Usually accuracy is poor at the lower end of scale which should be avoided. In such a situation, where accurate measurement is required throughout full range, two instruments with different ranges may be used, one […]

Classification of Methods of Measurements (Metrology)

1.6. In precision measurements various methods of measurement are followed depending upon the accuracy required and the amount of permissible error. There are numerous ways in which a quantity can be measured. Any method of measurement should be defined in such a detail and followed by such a standard practice that there is little scope […]

The Measurement Problem (Metrology)

1.7. In practice, we come across four basic conditions to be controlled by tolerances, viz, (a) size, (b) form, (c) location and (d) conditions of assembly, operation, or function. Fig. 1.5 illustrates these. The difference between sizes X and Y determines the assembly condition. Size conditions are generally simple to specify and control ; the […]

General Care of Metrological Equipment (Metrology)

1.8. The equipment (apparatus) used for precision measurements is designed to fine limits of accuracy and is easily liable to be damaged by even-slight mishandling and such damage may not be noticeable. A great deal of careful handling is, therefore, required. As far as possible, the highly finished surfaces should not be touched by hand […]

Objectives of Metrology

1.9. While the basic objective of a measurement is to provide the required accuracy at minimum cost, metrology would have further objective in a modern engineering plant with different shops like Tool Room, Machine Shop, Press Shop, Plastic Shop, Pressure Die Casting Shop, Electroplating and Painting Shop, and Assembly Shop, as also Research, Development and […]

Standardisation and Standardising Organisations (Metrology)

1.11. For overall higher economy, efficiency and productivity in a factory and country, it is essential that diversity be minimised and interchangeability among parts encouraged. All this is possible with standardisation. Standardisation is done at various levels, viz. International, National, Association, Company. Realising the role of standardisation in the development of industry, organisations to handle […]