The paper analyzes a pressure deviation issues in a vacuum technological process, which occurs due to vacuum gauge inaccuracies during its use. For this purpose a unique vacuum system was designed and used for research. Developed system allows verification of vacuum gauges in manufacturing conditions using various experimental settings for obtaining necessary measuring data and allowing to perform an evaluation about its accuracy, repeatability and the need of calibration. In the following research several experiments with ionization vacuum gauges were carried out to obtain performance data. Presented results and vacuum system allowed to develop a new methodology of vacuum gauge verification under manufacturing conditions.