Comparison of analogous and digital demodulation methods of modulated ultrasonic signals in vortex flow metering

Ultrasonic flow metering has become more important in the last few years because of contactless measurement. The latest results of research on topics like cross-correlation and vortex metering were published recently. Ultrasonic signals are modulated in amplitude and also in phase caused by effects in streaming fluids. In vortex metering the dominant reason of modulation is generated by Karman vortex street. Due to this effect every kind of modulation refers to a definite velocity. In vortex flow metering the vortex frequency is linear dependent on flow velocity. This article presents a comparison between analogous and digital demodulation techniques of modulated ultrasonic signals and shows the advantages and disadvantages of various principles.