THE CONSIDERATIONS AND GUIDES OF THE WATTMETER METHOD FOR MEASURING OUTPUT ACOUSTICAL POWER OF LANGEVIN-TYPE TRANSDUCERS - I - THEORY

The vibrational amplitude ratios of a number of positions in some typi cal vibration systems under different loads, especially of amplitudes at positions close to nodes and anti-nodes (related to no-load conditi ons) are given. Results according to the wattmeter method for measurin g output acoustical power and electro-acoustic efficiency of high-powe r ultrasonic vibration systems (Langevin-type transducers and horns) h ave been simulated, and theoretical errors of this method calculated. This points out that there are some limits for the wattmeter method in high load conditions, but the method has practical values for measuri ng output acoustical power, especially for sonochemistry. Finally, bas ed on the above analysis, some guidelines and suggestions for convenie nt on-line measurement are proposed. The vibration velocity of the rad iation surface is discussed as an important quantity in analyzing acou stic input in high-intensity ultrasound applications. (C) 1997 Elsevie r Science B.V.