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Overview of Metrology and Legal Metrology

  • Date:2019/04/10
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The oldest system of weights and measures in Chinese history derived from the huang-chung pitch-pipe.

The huang-chung pitch-pipe did not be handed down from past generations. Its earliest inscription was found in Yu Su clearly stating that weights and measures should be harmonized with the rhythm of a pitch-pipe. The surviving hsin-man-chia-lien measuring instrument at the National Palace Museum is the oldest official measuring standards refer to pitch-pipe in extant. The inscription on its body states: "harmonize weights and measures with the rhythm of the pitch-pipe." The significance of this inscription is that the instruments and the implementation of weights and measures were harmonized through "pitch."

The national primary measuring standards is under the custody of the BSMI. These and secondary measuring standards are both be periodically traced for calibration.
It is stipulated in the Weights and Measures Act that harmonization and implementation of metrology is conducted by the Bureau of Standards, Metrology and Inspection.

Legal Metrology

The Bureau of Standards, Metrology and Inspection (BSMI) under the Ministry of Economic Affairs is the competent authority for legal metrology. With a view to maintaining an effective national metrology system and to facilitating trade, the BSMI has been working towards promoting the use of international system of units, harmonizing national technical requirements for weights and measuring instruments with international requirements, and implementing a sound verification/inspection scheme in line with international practices.

Metrology is the science of measurement that includes units of measurement and their standards, measuring instruments and their fields of application, and all theoretical and practical problems relating to measurement. Metrology is classified in three main fields: scientific metrology, industrial metrology and legal metrology.

Legal metrology is defined in the International Vocabulary of Legal Metrology as the part of metrology relating to activities which result from statutory requirements and concern measurement, units of measurement, measuring instruments and methods of measurement and which are performed by competent bodies.

A legal measuring instrument means a measuring instrument that is designated by the competent authority for use in trade, certification, official inspection and testing or environmental protection activities, or is related to public safety and/or medical and health care affairs. The quality and creditability of legal measuring instruments are therefore important to ensure effective application in these areas.

The Weights and Measures Act is the regulatory basis for the BSMI in conducting its activities in the field of legal metrology. The Act was revised in January 2009 to incorporate important elements for implementing the national metrology system more effectively. These elements include the establishment of criteria for metrological engineers and technicians to ensure that verification of measuring instruments is done by qualified personnel, the establishment of a consumer volunteer scheme to strengthen market surveillance, the inclusion of manufacturers' self-verification approach to simplify the verification procedure, and the inclusion of physical volume tests for prepackaged goods.

The BSMI's activities in the field of metrology cover four areas, including establishment of national measurement standards, management of weights and measures industry, regulatory control of weights and measuring instruments, and regulatory control of prepackaged products. Specific details of each area are described respectively in the paragraphs below.

1. Establishment, Maintenance and Dissemination of National Measurement Standards

The BSMI develops techniques for absolute standards in scientific metrology, industrial metrology, and legal metrology. It establishes independent measuring standards and aligns national standards with international standards. It also provides the industry with calibration services that allow measuring standards to be traced to international standards.

2. Management of Weights and Measures Industry

Having recognized the impact on fair trade resulted from the use of weights and measuring instruments and the specific characteristics of the industry, the BSMI requires that a license obtained first in order for any person to be engaged in operating the business of manufacturing, repairing or importing measuring instruments so as to ensure adequate management.

3. Regulatory Control of Weights and Measuring Instruments

Measuring instruments employed for business transactions, public safety and health care purposes that are subject to metrological control as announced by the MOEA should be verified before sale or usage and should be inspected by the BSMI when they are in use. Except for a small range of measuring instruments (watt-hour meters, radar equipment for the measurement of the speed of vehicles, breath testers, evidential breath analyzers, sound level meters, and etc.) of which the verification is conducted by commissioned organizations assessed by the BSMI, almost all instruments are verified and inspected by this Bureau and its branches. All measuring instruments that pass verification will be inscribed, sprayed, branded, or lead-sealed with the logo and attached with a conformity sticker or issued a conformity certificate.

Measuring instruments that tend to drift after a period of time of service are required to be type-approved before verification with respect to their construction, material and performance, in order to ensure the stability of the measuring instrument and protect the rights of both transacting parties. The Ministry of Economic Affairs has currently announced that taximeters, water meters, diaphragm gas meters and electronic non-automatic weighing instruments are subject to type approval. The BSMI organizes a type approval committee to review the conformity of the appearance, structure and performance test results of sample instruments against relevant requirements. Once the type of an instrument has been approved, the BSMI issues a type approval certificate.

Regulations governing manufacturers' self-verification of measuring instruments were promulgated in August 2003. Conditions for manufacturers' self-verification include that manufacturers obtains ISO 9001 (CNS12681) certification, testing laboratories used are accredited, and the personnel performing verification must be certified metrology engineers or technicians.

4. Control of Prepackaged Products

Prepackaged products designated per public notice are required to be labeled with the information of net quantity, expressed by using the legal units of measurement. The difference between the labeled quantity and the actual quantity shall not exceed the statutory range of tolerance. Regulations governing the categories, labeling, sampling and relevant administration matters concerning prepackaged products subject to control are to be prescribed by the MOEA. The range of tolerances allowed for prepackaged products and other technical specifications are to be prescribed and published by the BSMI. Technical regulations for prepackaged products (physical volume test) were promulgated in September 2003. The scope includes administration of detergent and soap for laundry with net contents between 5 grams and 10 kilograms in weight, or between 5 milliliters and 10 liters in volume.

Along with the rapid changes in global trade, the main tasks for the BSMI is to move ahead by focusing on the research and development of metrological techniques, so as to provide adequate resources for the industry to use in meeting the challenges, and to maintain the integrity and traceability of standards systems to assure the secure and fair trade.

Conformity Assessment Procedures for Legal Measuring Instruments

* Type Approval

* Verification and Inspection

Management of Measuring Instruments Enterprises
Those who manufacture, repair or import measuring instruments must apply for permission and licensing from the BSMI

* The Business Operation Licensing and Administration Regulations of Measuring Instrument Enterprises