Primary measurement of ultrasonic power and dissemination of ultrasonic power reference values by means of standard transducers

The time-average ultrasonic power emitted by an ultrasonic transducer is on e of the key values characterizing the strength of ultrasonic fields as a w hole. For medical applications in particular, measurements are usually carr ied out in water and in the frequency range 1 MHz to 10 MHz. The use of a r adiation force balance is recommended in International Electrotechnical Com mission Standard TEC 61161. This measurement method and its practical reali zation at the Physikalisch-Technische Bundesanstalt are described. Uncertai nties involved in the primary measurement and in the dissemination process are discussed.