Standard for Metrology Instruments and Equipment
Metrology is the scientific study of measurements, and is essential for modern living. It plays a major role in practically every field of science and engineering, from measuring length or temperature of objects or materials, to accurately plotting the universe. As an internationally recognized branch of science and technology, metrology is governed by standards that are put in place by metrology specialists to ensure the quality and accuracy of measurements used in research, manufacturing, and other activities.
In the United States, the National Institute of Standards and Technology (NIST) is responsible for creating and maintaining the standards that govern metrology measurements. The NIST standard, the National Instrument and Equipment Standard (NIES), was developed to define the types of instruments and equipment that can be used to conduct accurate metrological measurements. The NIST standard defines four categories of metrology instruments and equipment that are vital to the overal quality and accuracy of metrological measurements: primary instruments and equipment, secondary instruments and equipment, reference instruments and equipment, and calibration instruments and equipment.
Primary instruments and equipment are those instruments and equipment that offer the highest possible accuracy and precision of measurements. Examples include such instruments as precision scales, microscope, or spectrograph. This level of instrument is typically used for research and development or for very specific types of measurements.
Secondary instruments and equipment are those instruments and equipment that provide adequate accuracy for most purposes, such as those needed for manufacturing and commercial establishments. This equipment is not as accurate as the more expensive primary instruments and equipment, but can be used in many areas with little difficulty. Examples include products such as non-precision scales, micrometers, and torque wrenches.
Reference instruments and equipment are those instruments and equipment that are generally used in metrology laboratories to calibrate and test other primary, secondary, and calibration instruments and equipment. Examples of reference instruments and equipment include such items as temperature calibrators, optical comparators, and precision callipers.
Finally, calibration instruments and equipment are those instruments and equipment that are used to calibrate primary, secondary, and reference instruments and equipment. This level of instrument is used for the application of traceable, repeatable standards of accuracy. Examples include thermometers, moisture testers, and photometric instruments.
The importance of these levels of instrument and equipment to the overall precision and accuracy of metrological measurements cannot be overstated. To ensure accuracy and repeatability, quality management systems require the use of instruments and equipment that are in compliance with the NIST standard for metrology instruments and equipment. In addition, any measurement that is used for trade or commerce should be taken with instruments and equipment that meet the national standards. By adhering to these standards, metrological measurements will be consistently accurate and dependable.
