Standard (metrology)

A detailed overview of standards in metrology

Introduction

The International Prototype of the Kilogram

In the field of metrology, a standard is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. Standards are essential for ensuring uniformity and consistency in measurements across different regions and industries. They serve as the reference points against which other measurements are compared.

Types of Standards

Primary Standards

Primary standards are the most accurate and precise standards available. They are maintained by national metrology institutes and are used to calibrate secondary standards. An example of a primary standard is the International Prototype of the Kilogram, which was used to define the kilogram until 2019.

Secondary Standards

Secondary standards are calibrated against primary standards and are used for routine measurements in laboratories and industries. They are less accurate than primary standards but are more practical for everyday use.

Working Standards

Working standards are used for the calibration of instruments and are typically calibrated against secondary standards. They are the most commonly used standards in industrial and laboratory settings.

Historical Development

Standard measures in Liverpool, England

The concept of measurement standards dates back to ancient civilizations, where units of measurement were often based on physical objects or human body parts. Over time, the need for more precise and universally accepted standards led to the development of more sophisticated systems.

In the 19th century, the Metric System was introduced, providing a standardized system of measurement based on the meter and the kilogram. This system laid the foundation for the International System of Units (SI), which is now the most widely used system of measurement worldwide.

Modern Standards

Modern metrology relies on a combination of physical artifacts and natural constants to define units of measurement. The International System of Units (SI) is based on seven base units, each defined by a specific physical phenomenon or constant.

Redefinition of the Kilogram

In 2019, the definition of the kilogram was redefined from being based on a physical artifact to being based on the Planck constant, a fundamental constant of nature. This change marked a significant shift in metrology, as it allowed for more precise and stable measurements.

Applications of Standards

Standards are crucial in various fields, including engineering, manufacturing, healthcare, and science. They ensure that measurements are consistent and reliable, which is essential for quality control, safety, and innovation.

Related Pages

• Metrology
• International System of Units
• Calibration
• Measurement

A set of gauge blocks used for precision measurement

Conclusion

Standards in metrology are fundamental to the accurate and consistent measurement of physical quantities. They provide the foundation for scientific research, industrial production, and international trade. As technology advances, the development and refinement of standards continue to play a critical role in ensuring precision and reliability in measurements.