Time domain evaluation of resonance antireflection (RAR) signals for ultrasonic density measurement

This paper presents an ultrasonic method for measuring the mass density of liquids with a solid layer separating a reference fluid and a test fluid. B y adjusting the frequency of the exciting signal according to the thickness of the layer, it is possible to generate destructive interference of the w aves reflected at the first and second boundary of the layer, Thus, the lay er appears to vanish for the incident waves. In the steady state the result ing echo signal depends only on the acoustic impedances of the reference fl uid and the test fluid and the interesting density can be extracted. Short- and long-term drifts of the electronics and the ultrasonic transducer impl ied are eliminated by using the well-known pulse-echo technique, with addit ional front-wave detection. The method presented here is a first step in de veloping an ultrasonic mass flow meter.