INTRODUCTION TO METROLOGY
Metrology is the science of measurement. It is concerned with the establishment, reproduction, conservation and transfer units of measurements and their standards.
Metrology is the study of different measuring instruments, precision and non-precision, accuracy and their errors and improving their accuracy.
Objectives of Metrology:
- To achieve standardization.
- To reduce the cost of inspection.
- To find the errors.
- To have good accuracy and precision.
- Selection of proper measuring instruments.
Types of Metrology:
- Scientific Metrology.
- Industrial Metrology.
- Legal Metrology.
Scientific Metrology: It is the development and establishment of measurement standards with their maintenance.
Industrial Metrology: It is the function of measuring instruments used in industry as well as in production.
Legal Metrology: It is covered with measurements which influence the transparency of economic transactions, health and safety.
Inspection is the act of checking of all materials, products and produced components, parts at various stages during manufacturing. It is the process of comparing materials, products and produced components with the established standards.
Inspection is very useful with all aspects in manufacturing to increase the productivity of the product and ensure that the product manufacture with its desired standards and specifications. It helps to co-ordinate the function of quality control, production, purchase and other departments of an organization.
It is defined as the agreement of the results of the measured quantity with its true value and measured value is called as an error. Accuracy is concerned with the true value. It is difficult and expensive to have good accuracy.
Precision is the repeatability of the measuring process. It shows how well identity preferred measurements agree with each other. Precision has no concerned with true value. It has no meaning for only one measurement, but exists only when a set of measurements is performed for same quantity under identical conditions.
It is the ability of a measuring device to detect small variations in a quantity being measured. The instrument is more sensitive when the ability of detection of an instrument is higher.
It is the ability of a measuring device to having its indication to convert to a meaningful number. To use of magnifying devices is desired to have good readability.
It is the ability of the measuring instrument to repeat the output readings consistently, when the same quantity is measured number of times under identical conditions.
It is the closeness of agreement between the results of measurements of the same quantity, when individual measurements are carried out by different observes, by different methods, using different instruments under different environmental conditions.
It is the process of framing of scale of the instrument by applying some standards. It is a pre-measurement process, carried out at the time of manufacturing.
It is the property of a result of a measurement or the value of a standard, whereby it can be related to references, usually national or international standards. Traceability means establishing a valid calibration of a measuring instrument.
Magnification means increasing the magnitude of output many times to made it more readable. It is made possible by using mechanical, electrical, optical, pneumatic principles.
Error is the difference between the measured value and the true value of the measured quantity.
Factors to be considered for the selection of measuring instrument:
- Cost of an instrument.
- Design and construction of an instrument.
- Precision of an instrument.
- Maintenance of an instrument.
- Sensitivity and readability of an instrument.
- Quantity to be measured.