Peculiarities of slow rate gas flow velocity measurement

Abstract

It is shown that the slow rate gas flow velocity it is purposive to measure by the continous ultrasonic pulse measuring method. It is suggested to probe the gas flow at equal time intervals simultaneously or alternately in both directions. In order to diminish the random errors it is proposed to increase the measuring rate and to average the results of many measurements. The increase number of measurements it may be achieved by using adjacent values of time propagation of signals upstream and downstream the gas flow. Another values of flow velocity it may be obtained by using the values of time propagation of signals downstream the flow and adjacent values of time propagation upstream the gas flow. On the basis of experimental investigation it is shown that the main influential factor which acts the zero drift of the ultrasonic measuring system is the instability of temperature of electronic unit. For minimisation of zero flow instability it is not enough to stop the natural convection of the gas by closing of only one end of the measuring spoolpiece. The gas motion is to be stopped at the both ends of the measuring section. Otherwise, the influence of natural convection it may be bigger than the zero drift of the ultrasonic measuring system and the results of measurement it would be distorted.