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During the certification processes for measurement management systems and quality assurance systems, auditors often encounter questions regarding how to distinguish between the verification of measuring instruments and the calibration of measurement equipment, as well as the differences in the validity of verification certificates and calibration certificates. The following is a discussion on this topic for the reference of those concerned. Definition of verification: Definition 1: Verification refers to the activity of determining and confirming that measuring instruments meet legal requirements; it includes inspection, marking, and/or issuing a verification certificate. JJF1001-2011 \"General Terms and Definitions in Metrology\", Clause 9.17 ； Definition 2: All the work carried out to evaluate the metrological performance of a measuring instrument and determine whether it is qualified. Article 61 of the Implementing Rules of the Metrology Law of the People’s Republic of China (hereinafter referred to as the \"Implementing Rules\"). Classification of metrological verification: According to the Metrology Law and its Implementing Regulations, metrological verification can be divided into mandatory verification and verification in accordance with the law. The meaning of calibration: 1. According to clause 4.10 of JJF1001-2011 \"General Terms and Definitions in Metrology\", it refers to a set of operations under specified conditions. The first step in these operations is to determine the relationship between the value provided by the measurement standard and the corresponding indicated value; the second step is to use this information to establish the relationship through which a measurement result can be obtained from the indicated value. In this process, both the value provided by the measurement standard and the corresponding indicated value have measurement uncertainties. 2. Clause 9.17 of JJF1001-1998 \"General Terms and Definitions in Metrology\": It refers to a set of operations carried out under specified conditions, in order to determine the value indicated by a measuring instrument or measuring system, or the value represented by a physical measuring tool or reference material, compared with the corresponding value reproduced by a standard. Note: (1) The calibration results can provide both the indicated value of the measured quantity and the correction for that indicated value. (2) Calibration can also determine other metrological properties, such as the effect of influencing factors. (3) The calibration results can be recorded in a calibration certificate or calibration report. Validity of calibration certificates: 1. For all social public measurement standards, the highest-level measurement standards used by departments, enterprises, and institutions, as well as those measurement instruments used in trade settlements, safety protection, healthcare, and environmental monitoring and listed in the **catalogue of measurement instruments subject to mandatory calibration, users must apply to a legal calibration institution authorized by the **measurement administration department for calibration; such instruments can only be used if they pass the calibration, and their calibration certificates must remain valid during that period. 2. For those measuring instruments for which laws or **mandatory standards require that they pass calibration before they can be used, and which are included in the \"Catalogue of Measuring Instruments Subject to Regulation under the Law of the People’s Republic of China\", enterprises may either carry out the calibration themselves to ensure compliance before using such instruments, or send them to a calibration institution authorized by the **metrology administrative department for calibration; the calibration certificate must also be valid during that period. 3. The calibration items carried out by the above-mentioned metrological calibration institutions must be within the specific items authorized by the metrological administrative department in order to be valid. Verification of the validity of measurement calibration certificates and reports: 1. The validity of measurement calibration certificates and reports is determined primarily based on **relevant laws and regulations, technical standards, technical specifications, or contractual provisions, as well as the specific technical requirements inherent in the enterprise’s production, processing, and testing processes. 2. Criteria for the metrological verification of the validity of calibration certificates: The metrological properties of calibrated measuring instruments or equipment must meet the metrological requirements of actual use. Such as measurement range, accuracy class, maximum allowable error, sensitivity, resolution, stability, measurement uncertainty, etc. Among them, the maximum allowable error and measurement uncertainty should generally be 1/5 to 1/10 of the measured object, with a minimum of 1/3. How to verify instrument and equipment calibration certificates/verification certificates