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The Input Strength of the Ultrasonic Signal
The stronger the inputted ultrasonic wave is, the stronger the received
echo will be. The strength of the input signal is mainly influenced by
the size of the emitter of the transducer. Large emitters can transmit
stronger energy to the material more than small ones.
Absorption and Scattering
Ultrasonic waves are capable of traveling through any material but are
partially absorbed by them. If the signal of the ultrasonic wave is
passed through air bubbles etc. included in the material, the sound
wave is scattered. This phenomenon reduces the signal and reduces
the performance of the thickness gage that detects the signal. The
higher ultrasonic wave frequencies are absorbed and are scattered
more than those of lower frequencies. Lower frequencies have
weaker directivity than higher ones. The transducer of higher
frequency is the better choice to detect the exact location of flaws,
cracks or pits.
The State, Roughness and Unevenness of a Surface
Material shape and the roughness of its surface are causes of
measurement failure. It is difficult for ultrasonic waves to penetrate
uneven surfaces and will result in unstable measurements or poor
reliability. The surface whose thickness is to be measured should be
clean and free of any small particulate matter, rust, or dirt. Make the
measurement surface clean and free from particles, rust or dirt. If any
of these obstructions are present, the transducer cannot make proper
contact. In general, clean the surface using a wire brush or sandpaper.
In special cases, clean the surface using a rotary sander or grinder.
Excessive scraping is not necessary. Measuring the very rough
surface like an uneven cast-iron surface is the most difficult. This
rough surface affects to the sound wave such that the light passes
through the frosted glass. The sound wave is absorbed and scattered
in all directions. Not only does the rough surface result in
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