Metrological research of a reference installation based on a high-pressure vessel

The urgency of development and metrological research of reference installations based on high-pressure vessels, which meet the requirements of the implementation of traceability of instruments for measuring gas volume and gas volume flow rate, is considered. The operation algorithm of the specified reference installations when transferring the unit of gas volume to the gas meters under consideration is studied. Based on the algorithm and features of the operation of PVTt-type standards, a list of the analysed uncertainties of type A is formulated when estimating the volume of the calibrated high-pressure vessel; when measuring the absolute pressure and absolute temperature of gas due to the influence of instability of pressure and temperature on the gas meter under consideration due to the presence of a temperature gradient in the vessel. Uncertainties of type B, which are determined by metrological characteristics of measuring instruments, as well as the uncertainty of parameters evaluated by means of calculation, in particular the compressibility factor of the working environment, the influence of water vapour on the working environment and the influence of the discreteness of the device for collecting information about measurements from the gas meter are considered. Formulas to quantify the combined uncertainty of measuring the volume of the calibrated vessel, the absolute pressure and absolute temperature as well as to calculate the air compressibility factor for the operating conditions of the installation are given. These parameters are the absolute pressure and absolute temperature of the gas and the compressibility factor of the working environment in the vessel at the beginning and at the end of the reproduction of the reference volume as well at the inlet of the gas meter. The expressions for calculating the combined and expanded uncertainties of PVTt-type standards are given.