Ultrasonic Continuous-Wave Beam-Power Measurements; International Intercomparison

Abstract

Some quartz transducers designed and fabricated at the National Bureau of Standards as transmitters of ultrasonic power appear to be sufficiently stable and linear to serve as standards.Therefore, an international intercomparison of measurements of the continuous-wave {cwl power emitted by these standards was arranged.Each of the seven participating laboratories performed such measurements using one or more methods representing its practice and reported the results to the National Bureau of Standards which served as the pilot laboratory.We present the results mostly in the fonn of tables.Some remarks on stability are appended. .Key words: intercomparison of standards; ultrasonic power standards; ultrasonic transducers.be the same, within the estimated.experimental errors, as that detel'mined at very low power by the twin-T null method.Other transducers were also calibrated by a calorimetric method, using an instrwnent designed and built by Zapf et al. [3] at NBS Boulder and modified at NBS Washington' .Each transducer was calibrated (twice) at only one power level which varied, from case to case, over the range 50 to 750 m W. Again, the values of G r agreed, within the estimated uncertainty, with those obtained by the other methods. ProcedureFour ultrasonic transducers were selected for the intercomparison.They were intended to be operated at the fundamental series-resonance frequencies; these, together with the designations, follow: ~The modifications.which were rather extensive, were made by Franklin R. Breckenridge and Carl E. Tschiegg.

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