
1-31
Chapter 1 Safety
Systematic Uncertainties
For the pulse intensity integral, de-rated rarefaction pressure (Pr.3), center frequency, and pulse
duration, the analysis includes considerations of the eects on accuracy of:
Hydrophone calibration drift or errors.
Hydrophone / Amp frequency response.
Spatial averaging.
Alignment errors.
Voltage measurement accuracy, including.
X
Oscilloscope vertical accuracy.
X
Oscilloscope oset accuracy.
X
Oscilloscope clock accuracy.
X
Oscilloscope Digitization rates.
X
Noise.
The acoustic power is measured using a Radiation Force for systematic uncertainties through the
use of calibrated NIST acoustic power sources.
We also refer to a September 1993 analysis conducted by the 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:
X
Balance system calibration.
X
Absorbing (or reecting) target suspension mechanisms.
X
Linearity of the balance system.
X
Extrapolation to the moment of switching the ultrasonic transducer (compensation for ringing
and thermal drift).
X
Target imperfections.
X
Absorbing (reecting ) target geometry and nite target size.
X
Target misalignment.
X
Ultrasonic transducer misalignment.
X
Water temperature.
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