National Standards Organization (ISO), International Electrotechnical Commission (IEC), International Organization of Legal Metrology (OIML), International Bureau of Metrology (BIPM), International Union of Pure Physics and Applied Physics (IUPAP), International Union of Pure and Applied Chemistry (IUPC) and 7 international organizations of the International Federation of Clinical Chemistry (IFCC) revised the International Vocabulary of Basic and General Terms in Metrology (hereinafter referred to as "VIM") in 1993. China ’s National Bureau of Quality and Technical Supervision in 1998 9 JJF1001-1998 "General Measurement Terms and Definitions" (hereinafter referred to as "JJF" national measurement technical specifications) was released in January. In the above two texts, there are precise definitions of measurement accuracy, flow instrument accuracy and accuracy level And instructions. Based on these documents, this article proposes issues that must be noted when using these concepts.
1. Accuracy
The corresponding English is accruacy (the word can be used to explain the measurement results, and can also 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 true value of the measured. When used for measurement Instrument is defined as the ability of the measuring instrument to give close to the true value. In all these cases, accuracy is a qualitative concept rather than quantitative. Therefore, accuracy is not like measurement error and measurement uncertainty, he is not There is no quantitative quantification of physical quantity. The measurement error is defined as the measurement result minus the true value of the measurement, which is the difference between the two quantities and can be given quantitatively. The accuracy cannot be. The so-called quantitative 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, and the value is given, -7.8mA. But we must not 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 (fiducialerrorofameasuringinstrument) of a measuring instrument is not greater than 0.01 (1%), it is often in accordance with the standard or Verification procedures, the accuracy of the instrument is level 1. But only the accuracy is level 1 and never the accuracy is 1%. Note: 1% is a quantity.
2. level of accuracy
In "VIM" and "JJF", the accuracy class (accuracyclass) refers to the measurement instrument meets certain measurement requirements, so that the error is kept within the specified limits of the measurement instrument grade and level.
Order and class are two different concepts in metrology. The measurement technical specification JJG1027-91 "Measurement Errors and Data Processing" has long been clarified. Etc. is a grade divided by the measurement uncertainty. The level is a grade divided by the magnitude of the indication error of the measuring instrument (for the definition of uncertainty and the definition of the indication error, including the definition of the indication error of the appliance, please refer to "JJF") For example, gauge blocks are both graded and graded, and standard batteries are graded and graded, while standard piston pressure gauges are graded but not graded. The level of some instruments is divided by reference error (a kind of relative maximum allowable error). We say that a measuring instrument conforms to a certain level or level, which qualitatively summarizes the accuracy of the instrument.
3. Quantification of accuracy
It is wrong to equate accuracy with measurement error or limit error or uncertainty, although all illustrate the ability to approach true values. The quantities that can be used for quantitative description are: measurement error, relative error, standard uncertainty u, extended uncertainty U and U; for measuring instruments, there are indication errors p, maximum allowable errors, reference errors of measuring instruments Wait. 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 the accuracy is 7.8mA, then this 7.8mA is an error? Is it the extended uncertainty with factor k = 2? Or is it the extended uncertainty of k = 3? Whether it is the maximum allowable error or the limit error is unclear. Therefore, if we want to quantitatively give the responsiveness of the measuring instrument close to the true value, we must specify what the given value is and cannot be called accuracy in a general sense.
The current misuse of the term accuracy is relatively common and should be given sufficient attention. Especially in the signing of contracts, accuracy is a term that cannot be quantified and cannot be checked and accepted based on it.
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