title: A constant-flow calorimeter for the measurement of acoustic power at megahertz frequencies.
abstract: The calorimeter absorbs, in a flow of castor oil, a fraction of the acoustic power output of an ultrasound transducer. It has been used to measure powere of between 1 mW and 10 W at frequencies from 1-5 to 3 MHz. Examples are given of results obtained for an ultrasound therapy unit and an ultrasonic pulse--echo scanner. Sources of inaccuracy are defined. It appears that constant-flow calorimetry offers a potentially very sensitive method for the absolute measurement of acoustic power.
mesh_terms: D002151:Calorimetry; D014464:Ultrasonic Therapy / Q000295:instrumentation; D014465:Ultrasonics / Q000295:instrumentation*; D014463:Ultrasonography