Elcometer 205 Operating Instructions Manual page 42

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A.2 Absorption and scattering
As ultrasound travels through any material, it is partly absorbed. If the materials through which the sound
travels have any grain structure, the sound waves will experience scattering. Both of these effects reduce
the strength of the waves.
Higher frequency ultrasound is absorbed and scattered more than ultrasound of a lower frequency. It may
seem therefore that using a lower frequency transducer might be better in every instance, however low
frequencies are less directional than high frequencies.
A.3 Geometry of the transducer
The physical constraints of the measuring environment sometimes determine the suitability of a transducer
for a given job. The transducer may simply be too large to be used in confined areas. Also, the surface area
available for contacting with the transducer may be limited. Measuring on a curved surface may require the
use of a transducer with a matching curved wearface.
A.4 Temperature of the material
When it is necessary to measure on surfaces that are exceedingly hot, special high-temperature
transducers may be necessary. Additionally, care must be taken when performing a 'Calibration to Known
Thickness' with a high temperature application - see "Measuring hot surfaces" on page 43.
A.5 Selecting the correct transducer
Elcometer have a complete range of transducers to meet your requirements, including:
• A range of frequencies and sizes
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