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I’m currently facing a challenge. My company is undergoing certification for its measurement management system. I’m not quite sure how to fill out the value traceability diagram. Could anyone with experience please advise me? The upper level refers to the metrology institute; the intermediate level includes the thermometers and electronic scales used by the company; the lower level relates to temperature measurements, etc. But I don’t know how to determine their uncertainty, maximum allowable range, and accuracy. How should these be filled in?Ningbo Metrology and Testing Institute: Metrological standard – Thermometer calibration device. Measurement range: (-200~1800)°C / (0~24)mA. Uncertainty: u=0.2°C, k=2.
Zhejiang Annuo Amines Chemicals Co., Ltd.: Measurement equipment – Thermometers. Measurement range: (0~1000)°C. Uncertainty: u=0.3°C, k=2. Measurement parameters – Temperature measurement. Measurement range: (-0.1~16) MPa. Accuracy: above grade 1.5.
Ningbo Metrology and Testing Institute: Metrological standard – Thermometer calibration device. Measurement range: (-200~1800)°C / (0~24)mA. Uncertainty: u=0.2°C, k=2.
Zhejiang Annuo Amines Chemicals Co., Ltd.: Measurement equipment – Thermometers. Measurement range: (0~1000)°C. Uncertainty: u=0.3°C, k=2. Measurement parameters – Temperature measurement. Measurement range: (-0.1~16) MPa. Accuracy: above grade 1.5.
Ningbo Metrology and Testing Institute: Metrological standard – Thermometer calibration device. Measurement range: (-200~1800)°C / (0~24)mA. Uncertainty: u=0.2°C, k=2.
Zhejiang Annuo Amines Chemicals Co., Ltd.: Measurement equipment – Thermometers. Measurement range: (0~1000)°C. Uncertainty: u=0.3°C, k=2. Measurement parameters – Temperature measurement. Measurement range: (-0.1~16) MPa. Accuracy: above grade 1.5
When the measurement uncertainty is expressed in terms of the standard deviation σ, it is called the standard uncertainty; it is conventionally denoted by the lowercase Latin letter “u”, and this is the first way of representing measurement uncertainty. However, since the confidence level corresponding to the standard deviation (also known as the confidence probability) is usually not high enough – at only 68.27% in the case of a normal distribution – it is also specified that the measurement uncertainty can be expressed in a second way, namely as a multiple of the standard deviation, kσ. This type of uncertainty is called expanded uncertainty, and it is uniformly denoted by the uppercase Latin letter U. Thus, the relationship between the standard uncertainty and the expanded uncertainty can be obtained: U = kσ = ku, where k is the coverage factor. The expanded uncertainty U represents the half-width of the interval at a higher confidence level. The inclusion factor is sometimes also written in the form of kp; when multiplied by the combined standard uncertainty uc(y), it yields the expanded uncertainty Up=kpuc(y) corresponding to a confidence level of p. In uncertainty assessment, the symbols for various types of uncertainties are uniformly specified; to avoid misunderstandings, they should generally not be changed arbitrarily. In practical use, it is often desirable to know the confidence interval of the measurement results; therefore, it is also specified that the measurement uncertainty can be expressed in a third way, namely by the half-width a of the interval indicating the confidence level. In fact, it is also a type of expanded uncertainty; when the specified confidence level is p, the expanded uncertainty can be denoted by the symbol Up.