International Organization for Standardization (ISO), International Electrotechnical Commission (IEC), International Organization for Legal Metrology (OIML), International Bureau of Metrology (BIPM), International Union of Pure and Applied Physics (IUPAP), International Union of Pure and Applied Chemistry (IUPC) and the International Federation of Clinical Chemistry (IFCC) 7 international organizations revised the "International Vocabulary of Basic and General Terms in Metrology" (hereinafter referred to as "VIM") in 1993. Our country The Bureau of Quality and Technical Supervision issued JJF1001-1998 "General Metrology Terms and Definitions" (hereinafter referred to as "JJF" National Metrology Technical Specifications. In the above two texts, the accuracy of measurement, the accuracy of flow instruments and the The accuracy levels have precise definitions and explanations. Based on these documents, this article puts forward the issues that must be paid attention to when using these concepts.

1. Accuracy

The corresponding English is accruacy (this word can be used to describe the measurement results, but also can be used to indicate the value of the measuring instrument. When used in the measurement result, it indicates the degree of agreement between the measurement result and the measured true value. When used in the measurement When measuring an instrument, it is defined as the ability of a measuring instrument to give a value close to the true value. In all these cases, accuracy is a qualitative concept rather than quantitative. Therefore, accuracy is not like measurement error or measurement uncertainty. There is no quantitative determination of physical quantity. Measurement error is defined as the measurement result minus the true value of the measured value. It is the difference between the two quantities and can be given quantitatively. Accuracy cannot be given. The so-called quantification is the expression of the quantity value. For example, We say that the indication error of a measuring instrument is -7.8mA, which is a quantitative expression, giving the value of -7.8mA. But we can never say that the accuracy of this measuring instrument is -7.8mA or It is ±7.8mA, or less than or equal to 7.8mA. When the reference error of a measuring instrument (fiducial
When the error of a measuring instrument is not greater than 0.01 (1%), the accuracy of the instrument is usually level 1 in accordance with the standards or verification procedures related to the instrument. However, the accuracy is only level 1 and the accuracy is by no means 1%. Note: 1% is a quantity.

2. level of accuracy

In "VIM" and "JJF", accuracy class (accuracy class) refers to the class and level of the measuring instrument that meets certain measurement requirements and keeps the error within the specified limit.

Order and class are two different concepts in metrology. The measurement technology specification JJG1027-91 "Measurement Error and Data Processing" has long been clear. Etc. is a grade divided by the size of measurement uncertainty. Level is a grade divided by the size of the indication error of the measuring instrument (for the definition of uncertainty and the definition of indication error, including the definition of indication error of appliances, please refer to "JJF"). For example, the gauge blocks are graded and graded, the standard battery is also graded and graded, while the standard piston pressure gauge is only graded and not graded. The level of some meters is divided by reference error (a kind of relative allowable error). We say that a measuring instrument meets a certain class or level, which qualitatively sums up the accuracy of the instrument.

3. The quantitative problem of accuracy

It is wrong to equate accuracy with measurement error or limit error or uncertainty, although both show the ability to approach the true value. The quantities that can be used for quantitative explanation are: measurement error, relative error, standard uncertainty u, expanded uncertainty U and U; for measuring instruments, there are measuring instrument's indication error p, allowable error, quoted error, etc. . When these quantities are given, a quantity can be given without exception. We can think of accuracy as just a general term for them. If we say that the accuracy is 7.8mA, then this 7.8mA is an error? Is the expanded uncertainty of the inclusion factor k=2? Or the extended uncertainty of k=3? It is not clear whether it is the allowable error or the limit error. Therefore, if we want to quantitatively give the response ability of a measuring instrument close to the true value, we must specify what the given value is and cannot be called accuracy.

The current misuse of the term accuracy is more common and should be paid attention to, especially in the signing of a contract. Accuracy is a term that cannot be quantified and cannot be used for inspection and acceptance, which may easily lead to undue losses.