
Chapter 1 Safety
1-31
The systematic uncertainties Acoustic power measurements using a Radiation Force are measured
through the use of calibrated NIST acoustic power sources.
We also refer to a September 1993 analysis done by a working group of the IEC technical committee 87
and prepared by K. Beissner, as a rst supplement to IEC publication 1161.
The document includes analysis and discussion of the sources of error / measurement eects due to:
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Balance system calibration.
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Absorbing (or reecting) target suspension mechanisms.
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Linearity of the balance system.
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Extrapolation to the moment of switching the ultrasonic transducer (compensation for ringing and
thermal drift).
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Target imperfections.
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Absorbing (reecting) target geometry and nite target size.
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Target misalignment.
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Ultrasonic transducer misalignment.
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Water temperature.
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Ultrasonic attenuation and acoustic streaming.
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Coupling or shielding foil properties.
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Plane-wave assumption.
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Environmental inuences.
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Excitation voltage measurement.
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Ultrasonic transducer temperature.
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Eects due to nonlinear propagation and saturation loss.
The overall ndings of the analysis give a rough Acoustic Power accuracy gure of +/- 10% for the
frequency range of 1 - 10 MHz.
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