Metrology comes from the Greek word “metron" and “logos" which literally means the study of measurement. This study covers both the experimental and theoretical aspects of measurement and the determination of the levels of uncertainty of these aspects. The study of measurement is a basic requirement in any field of science and technology, most importantly in engineering and manufacturing. Since metrology is the study of measurement, it is expected to enforce, validate and verify predefined standards for traceability, accuracy, reliability, and precision. All of these are factors that would affect the validity of measurement. Although these standards vary widely, these are mandated by the government, the agencies, and some treaties. Consequently, these standards are verified and tested against a recognized quality system in calibration laboratories.
The experimental aspect of metrology is that which deals with the investigation of the relationship among variables. These variables are established depending on set of observations being considered or classified. As such, it is in this aspect that hypotheses are established and tested.
On the other hand, the theoretical aspect of metrology deals with the various concepts and principles underlying the study. This aspect is based on established theories and concepts which are derived from empirical observations which satisfy the baseline requirements. In other words, the theoretical aspect is expected to be functional and working.
In order to thoroughly grasp the concept of measurement, metrology is divided into three subfields. These three subfields in metrology are: scientific or fundamental metrology, applied or industrial metrology, and legal metrology. Each of these subfields is distinctly different from the other.
Scientific or Fundamental Metrology. This subfield deals with the establishment of units of measurement, unit systems, and quantity systems. The units of measurement sets standards adopted conventionally and by law, of the definite magnitude of a physical quantity. On the other hand the units systems are composed of the traditional systems, metric systems, and the natural systems. There are also some unit systems that are derived from a set of fundamental units. The quantity systems are the standard systems used in the control of measure, net weight, or number of constant quantity packed goods.
Moreover, scientific metrology goes beyond than just the establishment of units, and includes the realization of these standards to the users in the society; and the development of new methods in measurement.
Applied or Industrial Metrology. Applied metrology is rather specific in its applications, which are primarily various industrial processes including manufacturing among others. This metrology subfield intends to establish the importance of measurement in the industry. Moreover, it also ensures the appropriateness of measurement instruments including the maintenance, quality control, and proper calibration of these instruments.
Legal Metrology. For the protection of life, the environment, health, and public safety, regulatory requirements of measurement and measurement instruments have to be looked after. These are the concerns of legal metrology. With the objective of regulating appropriate rules and regulations pertaining to measurement, and measurement instruments as well; the consumers are definitely protected and guaranteed that fair trade is observed.