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What is the difference between a calibration certificate and a verification certificate?

First, the technical basis used is different

The "Measurement Law" clearly stipulates that the measurement verification work must be strictly implemented in accordance with the national measurement verification system table for the measurement verification work; the measurement calibration work shall use the current and valid national measurement and calibration specifications corresponding to the calibration items or refer to the corresponding When there is no national metrological calibration specification or corresponding metrological verification regulations, a calibration method that meets the needs of calibration prepared according to international, regional, national or industry standards can be used as the calibration basis.

Two different conclusions on the measurement results

When measuring the measuring instrument, the verification result must clearly indicate compliance, that is, "pass" or "unqualified"; and the calibration certificate only provides complete calibration data and the uncertainty of the measurement result. As for the calibration and measurement, Whether the appliance can be used, the measurement personnel need to reconfirm based on these data.

Three certificates have different validity periods

The metrological verification should strictly implement the metrological verification regulations, and the verification regulations have clear provisions for the verification cycle of the corresponding measuring instruments, so the verification certificate issued by the verification agency will also have a clear validity period mark. The calibration certificate gives the date of “recommended school”, which does not specify the validity period of the certificate.

Four different legal effects

The "Measuring Law" stipulates that working measuring instruments included in the national compulsory measurement verification catalog, measuring standard instruments and main ancillary equipment included in the measurement standard assessment scope must be subject to measurement verification, and other measuring instruments can be sent to inspection or school according to their own needs. This requires the measurement personnel to be familiar with the measuring instrument used, otherwise the verification certificate should be issued for the measuring instrument submitted for inspection, but the calibration certificate will be returned, which will greatly affect the measurement results of the measuring instrument.

Five measurement results are given in different ways

In the verification work, in accordance with the provisions of JJF1104-2003 "Rules for the Preparation of National Metrological Verification System Tables", the ratio of the uncertainty of the measuring instrument used as a reference standard to the maximum allowable error of the tested instrument is less than 1: 3, as long as the verification The regulations require verification. When evaluating the tested instrument, the influence of the measurement uncertainty of the reference standard may not be considered. Therefore, what appears in the verification certificate is that the measurement result is directly compared with the specified limit, and the measurement is not performed. Uncertainty assessment is made as a result. However, the calibration certificate only gives the calibration result and does not make a statement of compliance. Whether the instrument meets the measurement performance requirements must be determined by the user according to the calibration result and the purpose of use. This requires that the measurement uncertainty must be included in the calibration certificate along with the calibration result. Give together. In fact, this is also the requirement for calibration results in CNAS CL01: 2006 "Guidelines for the Accreditation of Testing and Calibration Laboratories" and JJF1069-2012 "Specifications for Statutory Metrological Inspection Institutions".

Updated: 2019-11-11
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