The temperature of a transducer sensitive element, as a result of its heat capacity, will always lag behind the temperature of the gas flow if this temperature changes. When measuring the flow temperature that varies in time, the transducer doesn't follow the changes in temperature immediately because its sensitive element temperature changes after some time. The distortions of the transducer readings are caused by the thermal inertia due to non-stationary heat processes in the transducers, as well as between transducer and the environment. Since complete elimination of real temperature transducer inertia is not possible, the transducers with some finite values of the thermal inertia are used at practice to measure the varying gas flow temperature. The necessary information about the flow temperature can be obtained by analyzing the record of the non-stationary measurement process. In this case a direct calculation of the flow temperature is made or a correction of the temperature transducer readings delay is made. The results of research and analysis of measurement methods of rapidly changing gas flow temperatures by the direct calculation of the flow temperature and by correcting the temperature transducer readings are presented in this paper.

Methods for measuring the roughness of the internal surface of a measuring pipeline for projected rectilinear sections of a measuring pipeline and for rectilinear sections that are in operation have been determined. The new equations for calculating the hydraulic resistance coefficient of friction of natural gas on the internal surface of the measuring pipeline, the average value of natural gas pressure along the section of a measuring pipeline and the equivalent roughness were obtained. These equations provide improvement of accuracy of natural gas flow rate and volume measurement by means of the differential pressure method. The equation for calculating the Reynolds number from the conditions of the roughness measurement in real time was obtained. The technique of selection of methods of the roughness measuring was presented. Functional scheme of process automation of measurement the equivalent roughness of the internal surface of the measuring pipeline was developed.

In order to improve the accuracy of gas flowrate measurement by means of the differential pressure flowmeters, it is necessary to apply equations for determination of coefficients of gas flow equation, which would provide the lowest total relative expanded uncertainty of calculation, and to increase the accuracy of input values measurement in real time. One of these values is the arithmetic mean deviation of roughness profile of pipe internal surface. The equation for calculating the arithmetic mean deviation of roughness profile of pipe internal surface in real time was obtained. The equation for calculating the total relative expanded uncertainty of measurement result of arithmetic mean deviation of roughness profile of pipe internal surface in real time and components of this uncertainty were obtained.