In modern companies, increasing importance is attached to various measurements and analysis of the results obtained. This master's thesis presents the preparation and verification of diaphragm gas meters as currently the only one of the most used gas flow meters in Croatia, but also in the world. The purpose of this thesis is to present the theoretical framework respectively logical models and conclusions reached by various studies, which contribute to the understanding of the preparation and verification of membrane gas meters. Furthermore, a number of laws and regulations that are necessary to understand the analyzed area are presented. The master`s thesis performs a detailed analysis of the preparation and verification of gas meters, on the example of a diaphragm G4 gas meter in the company Termoplin d.d. Varaždin, which can serve as a positive example of continuous improvement and development of this area. The analysis of the presented data indicates that the preparation and verification of gas meters are indeed extremely important for the business of companies engaged in this activity. A key issue in this master`s thesis is the measurement uncertainty of the devices used to test gas meters, which really affects various aspects of the company's business.