Current thoughts from the National Conference on Weights and Measures (NCWM) and the National Type Evaluation Program (NTEP)

摘要

The United States is unique in many ways, and legal metrology is no exception. Unlike most industrialized countries in the world, the United States does not have a federalized legal metrology system. The individual states, via the Weights and Measures Laws adopted by and in force in each state, govern the regulation of weighing and measuring devices used in commerce. However, like many other countries around the world, the US does have a similar approach to legal metrology control. This includes type evaluation/certification, initial verification and subsequent verification. (Note: in the US the term "device" can currently refer to a weighing or measuring main element, a system or a measuring instrument). The concept of pattern approval or type evaluation, as it is better known in the US, is not a new idea. Back in the late 1960s, the National Bureau of Standards (as it was called then) began issuing "Reports of Test". At this same time, many states had set up laboratories and required measuring instruments to be evaluated and certified before they could be placed in service within that state. In some cases, states would recognize the Certificates issued by other states. In all, there were at least 18 different possible Certificates that a company might be required to obtain before it could install a measuring instrument in all the various states in the US. In the mid-1970s work began to create a National Type Evaluation Program (NTEP). NTEP became operational in October 1984. Gradually, states began recognizing NTEP Certificates of Conformance that were at that time issued by the National Institute of Standards and Technology (NIST). This could be considered a Mutual Acceptance Arrangement agreed to by the states in the US.