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Explain the fundamental Principles of metrology?
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Introduction

  • The importance of metrology as a scientific discipline gained momentum during the industrial revolution.

  • Metrology is practiced almost every day, often unknowingly, in our day-to-day tasks. Metrology concerns itself with the study of measurements.

  • In addition, metrology is also concerned with the reproduction, conservation, and transfer of units of measurements and their standards. Measurements provide a basis for judgements about process information, quality assurance, and process control. It is also concerned with the correctness of measurement.

  • In order to test whether functioning of the elements constituting the product/system meets the design expectation, and to finally assess the functioning of the whole system, measurements are inevitable.

  • This course is intended for any engineer involved in measurements, which may be in manufacturing and process control, in development, troubleshooting, or research.

  • Specialist knowledge is not a prerequisite, and should gain insight into the equipment and methods commonly used, and develop a healthy skepticism about instrument readings.

  • The basic message of the course is that while an instrument may in itself be highly accurate, the way in which it is applied can render the results highly inaccurate.

  • The aim is to help the engineer avoid, or at least minimize, these inaccuracies.

  • Many of the commonly used measurement methods are described, together with their pitfalls and problems, interspersed with practical examples.

Metrology

  • Metrology helps extract high-quality information regarding the completion of products, working condition, and status of processes in an operational and industrial environment.

  • The quality of the products influences various production attributes such as continuity, production volume and costs, productivity, reliability, and efficiency of these products with respect to their application or their consumption in a diverse manner.

  • Metrology is an indispensable part of the modern day infrastructure. In fact, it plays an important role in our lives, either directly or indirectly, in various ways. In this competitive world, economic success of most of the manufacturing industries critically depends on the quality and reliability of the products manufactured-requirements in which measurement plays a key role.

Objectives of Metrology and Measurements

The objectives of metrology and measurements include the following:

  1. To ascertain that the newly developed components are comprehensively evaluated and designed within the process, and that facilities possessing measuring capabilities are available in the plant.

  2. To ensure uniformity of measurements.

  3. To carry out process capability studies to achieve better component tolerances.

  4. To assess the adequacy of measuring instrument capabilities to carry out their respective measurements.

  5. To ensure cost-effective inspection and optimal use of available facilities.

  6. To adopt quality control techniques to minimize scrap rate and rework.

  7. To establish inspection procedures from the design stage itself, so that the measuring methods are standardized.

  8. To calibrate measuring instruments regularly in order to maintain accuracy in measurement.

  9. To resolve the measurement problems that might arise in the shop floor.

10.To design gauges and special fixtures required to carry out inspection.

  1. To investigate and eliminate different sources of measuring errors.

Terminology

  • Traceability :The process of validation of the measurements to ascertain whether the given physical quantity conforms to the original/national standard of measurement.Calibration Calibration is a means of achieving traceability.

  • Scale factor:If the instrument has an arbitrary scale, the indication has to be multiplied by a factor to obtain the nominal value of the quantity measured.

  • Static calibration:If the values of the variable involved remain constant (not time dependent)while calibrating a given instrument.If the value is time dependent or time-based information is required.

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