ULTRASONIC RESONATOR ENERGY-LOSS DETERMINATION

Ultrasonic resonators are used to study chemical kinetics in liquids (relaxation spectrometry). Resonator loss, proportional to Q-1, is frequently determined from half-power bandwidth (amplitude 3 dB down from peak value); but other methods, in particular those utilising the phase characteristic at resonance, are often advantageous. The author describes three different techniques, employing an AM driving signal for the resonator network, affecting the modulation envelope; a resonance peak compensation (RF amplitude and phase of the output signal); the phase slope (group delay) of the output signal. Relations for the one-dimensional ultrasonic resonator, circuit diagrams and measurement examples are given.