Practical ultrasonic spectrometric measurement of solution concentrations by a tracking technique

The authors designed and tested a practical measurement technique for solutions, based on a resonator with enclosed piezoceramics which can operate at a resonant frequency mode around 500 kHz. The resonance can be tracked automatically by means of a phase-locked loop. The authors report measurements made on water-methanol mixtures, showing that concentration can be expressed as a function of temperature and resonant frequency. Concentration could be evaluated with a precision of about 0.04% which depends essentially on the temperature measurement. Various milk mixtures have also been measured, to check the evaluation of fat, solid nonfat, and protein concentrations from measurements at two different temperatures. The system was designed to be eventually portable for field measurements