Two-layer calorimeter with thermally insulating separator for measuring ultrasonic power

Abstract The uncertainty in ultrasonic power measurement via calorimetry for high-power ultrasound is known to be larger than that via the radiation force balance (RFB) method. In order to achieve low uncertainty, we developed a two-layer calorimeter with a thermally insulating sheet to reduce the effect of heat generation by the ultrasonic transducer, which is a large factor in calorimetric uncertainty. The effect of the thickness of the separating sheet on ultrasound propagation and heat transfer was evaluated via simulations. A two-layer calorimeter with a 0.1-mm-thick thermally insulating sheet exhibited results close to those obtained via the RFB which is the most accurate method between 10 W–20 W. Also, we successfully measured ultrasonic power up to 100 W with this calorimeter. The results revealed that the two-layer calorimeter successfully suppressed the effect of heat generated by ultrasound transducers. This may lead to a reduction of the uncertainty in calorimetry.