Travel time measuring system for flow rate determination - compares signals from two spaced probes by storing and delaying first signal until it agrees with second

摘要

Flow rate or flow rate variation is measured by recording the travel time between two probes spaced along the flow path. The probes measure time variable characteristics of the flow medium, the variable measuring signals being converted into analogue voltages. The measuring signal from the first probe is stored and is subjected to a variable delay, before being continuously compared with the signal from the second probe. This delay is adjusted until the two signals agree, with the momentary delay time providing the travel time between the probes. Pref. the delay is adjusted until the absolute square difference of the two signals is min. The system can also be used to measure current phase shifts, sound propagation rates etc.