Sonic measurement of gas flow

摘要

A microcomputer is interfaced to a pair of probes for sending and receiving sonic signals across a flow stream of gas. The microcomputer reads phase information and determines a phase difference that corresponds to a difference in travel times for two oppositely directed sonic signals. The microcomputer is also interfaced to a load cell that communicates with the flow stream through two valve-controlled gas lines. The microcomputer controls the valves to trap a sample of the gas and to allow the gas to attain two different pressures. By measuring changes in pressure and weight for a fixed volume of the gas, the microcomputer can determine sonic velocity. It then uses this result and the phase difference determined from the sonic measurement to calculate flow rate and to generate an output signal proportional to the flow rate of the gas.