Calorimetric method for measuring high ultrasonic power using water as a heating material

The present study shows the calorimetric method for measuring high ultrasonic power using water as the heating material. In recent years, at the National Metrology Institute of Japan (NMIJ), an ultrasonic power primary standard of from 1 mW to 15 W has been established by the radiation force balance (RFB) method. Conventionally, the RFB method is widely used for ultrasonic power measurement, but this method is not suitable for very high power measurement due to thermal damages to the absorbing targets. High power ultrasonic standards, however, are being required by medical HITU measurements and in the sonochemistry industry. In order to meet these requirements, we have started to develop an ultrasonic power standard between 15 W and 200 W. Our final goal is an ultrasonic power standard of up to 500 W. The calorimetric method is an alternative ultrasonic power measurement method to the RFB method. We have adopted this method and use water as the heating material. Water has excellent features as a standard material, because the physical properties of water are well known. In the present study, we present an experimental system and the results for an ultrasonic power standard of up to 100 W. The measured ultrasonic power agreed well with the NMIJ primary standard up to 25 W.