Measurement standards/reference materials

1. Measurement standards/reference materials

(1) “Measurement” represents the foundation of science and technology as well as that of the economy and society

“Measuring” is indispensable in activities such as observing the natural world and creating things.

・ An artificial satellite represents an assemblage of assorted measuring instruments launched into the space.

・ Substances of several microns (1/1000 millimeters) are processed at semiconductor plants.

(2) “To measure accurately”

Unified “units” and “measuring instruments” are necessary to judge whether the measured values are accurate or not.

(3) “Units” and “measuring instruments”

There are seven types of “units” for “measuring” standards and are defined as follows internationally.

Amount	Unit	Definitions
Length	m	Distance for which light travels through a vacuum in 1/299,792,458 seconds
Mass	㎏	Equal to the mass of international kilogram
Time	s	Duration of 9,192,631,770 times of an emission cycle corresponding to the succession of the cesium-133 atomic ground state between two ultrastructure units
Current	A	Certain current that flows both of two infinitely-long linear conductors, which are set in parallel one meter apart in a vacuum and have infinitely-small circle cross-section area, and mutually exerts a force of 2×10^-7 newtons per meter on these conductors
Temperature	K	1/273.16 of thermodynamic temperature of the triple point of water
Substance quantity	mol	Substance quantity of series that contain the same number of elementary entities as atoms existing in carbon 12 (0.012 kilograms)
Luminance	cd	Luminance in certain direction of a light source that emits monochromatic radiation of 540 terahertz and has radiant intensity of 1/683 watts/steradian in the direction in question

Furthermore, “measuring instruments” that realize the above-mentioned definitions need to be created.

Standard instruments with the greatest accuracy that realize the above-mentioned definitions　→　Measurement standards

Materials such as liquid and gas whose purity and density are measured with the greatest accuracy based on the above-mentioned definitions　→　Reference materials

Current conditions of the system for providing measurement standards (Proofreading by specified standard instruments) PDF (Japanese only)

Request reception concerning development of measurement standards

Linked to the website of the National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology

2. Measurement of the length by measurement standards/measurement of the density by reference materials

(1) Measurement of length by measurement standards

A standard ruler should be created by using iodine-stabilized He-Ne laser, which is a measurement standard of the length. The length is measured by double-checking the results produced by a length measurement instrument based on this standard ruler.

(2) Measurement of the density by reference materials

The density is measured by comparing an analysis chart when measuring a sample including materials of known quantity (reference material) with an analysis chart when measuring the object.

3. Research and development concerning measurement standards and reference materials

Realization and provision of measurement standards with the greatest accuracy worldwide

In Japan, the National Institute of Advanced Industrial Science and Technology conducts research and development concerning measurement standards and reference materials.

(1) Mass standard/Japan prototype kilogram (1.000 000 176kg)

The mass can be measured with the accuracy of ±0.0000000001kg by accurately correcting errors caused by buoyancy receiving from the air, magnetic force, and the mass of gas molecules attached to the surface, etc.

(2) Length standard/Iodine-stabilized He-Ne laser (wavelength 633nm)

The length can be measured with the accuracy of 1m±0.00000000001m by enhancing the purity of iodine and accurately correcting errors.

(3) Time standard/Cesium atomic clock

The time can be measured with the accuracy of 1 second±0.0000000001 seconds by accurately correcting errors caused by magnetic field and gravitational potential.

(4) Reference materials/Various inorganic reference materials

The above are responsible for refining and providing reference materials with the accuracy of ±1% with regard to various metal solutions necessary for monitoring the quality standard of tap water and natural water.