Quantitative ultrasonic interferometry applicable to differential transit time flow measurement: preliminary report

The relative phase of two interfering coherent signals may be quantitatively derived from the amplitudes of the incident signals and the combined, destructive interference signal. The authors applied this concept to measurement of the small differences in transit time between two wave trains of ultrasound simultaneously traversing water flowing through a traditional (3 cm) differential transit time ultrasonic flow transducer. Preliminary tests with a passive ultrasonic interferometer validate the approach and demonstrate applicability to measurement of blood and other fluid flows.