In quality control, it is common practice to measure quality using measuring instruments, understand it as a phenomenon, and then quantify and manage it.
So, what is "measurement"? It is used as a general term for the entire process of measuring, which involves devising means and methods for measuring, taking the measurement, and using the results, in order to grasp things quantitatively with a specific purpose in mind. Furthermore, "measurement" refers to using a certain quantity as a standard (basic quantity), comparing it with a target quantity, and expressing it using a numerical value (or sign) (measured quantity).
While "measuring instrument" and "instrument" each have their own meanings, they are such common words that they are often used without much thought to their distinction.
To quantify quantities, a fixed size of quantity used as a standard is called a "unit." For length, this is a "meter," for mass, it's a "kilogram," and for time, it's a "second." The unit of a "basic quantity" is called a "basic unit," and for length, it's 1 meter. Using a "subsidiary unit," it could be, for example, 1,000 mm.
To give universality to measurements, a method (or object) of representing the magnitude of a quantity used as a reference is called a "standard," and a concrete example of this is called a "standard instrument."
"Traceability" indicates that standard instruments and measuring instruments are successively calibrated by higher standards, establishing a pathway that leads to national standards. To ensure fair trade, measurements based on officially established standards such as the "Measurement Law" are sometimes called "measurement." Scales used when selling goods by weight are designated as weight measuring instruments, and sound level meters are designated as sound level meters.
The International System of Units (SI) exists with the aim of global standardization. In Japan, the use of SI units is mandated by the Measurement Law, and current measuring instruments display "measured quantities" in SI units, and these instruments are calibrated to be linked to national standards through "traceability."
The National Metrology Institute of Japan (NIMS) of the National Institute of Advanced Industrial Science and Technology (AIST) has an explanation about "measuring standards."
What is a metrological standard?
(Excerpt from the email newsletter issued on January 25, 2002)
