JJG 920-2017 in English

This document outlines the procedures and requirements for the verification of transmittance visual density meters. It provides detailed guidelines on the technical specifications, calibration methods, and performance criteria that these instruments must meet to ensure accuracy and reliability in measurements. The content includes instructions for the initial inspection, calibration process, and subsequent verification intervals. Additionally, it specifies the environmental conditions under which the verification should be conducted, as well as the necessary equipment and reference standards. The document is structured to facilitate consistent application across different verification facilities and ensures that the results obtained are comparable and traceable. It also covers the documentation and reporting requirements for the verification process, ensuring transparency and accountability in the calibration of transmittance visual density meters.