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CHAPTER SEVEN
TRANSDUCER SELECTION
7.1 Selecting the Transducer
Transducer selection is a very import part of getting the best results from the
MiniMax. The frequency and diameter of transducer should be carefully selected
using the following information:
Select the largest diameter transducer that will seat completely on the end of the
bolt.
If there are multiple applications and diameters to consider, select a
diameter that will work for as many applications as possible, thus reducing the
overall number of transducers needed.
When selecting the proper frequency, the following items should be taken into
consideration:
Higher frequencies are typically a better choice when measuring smaller
diameter bolts as the sound is better focused resulting in less beam spread
and more directivity.
Lower frequencies are more forgiving of potential bending and attenuative
materials. This is primarily due to the longer wavelength avoiding smearing or
distortion of the waveform. Longer wavelengths require more of a phase shift
before distortion will occur. Lower frequencies offer an increased amount of
dispersion and a reduced amount of directivity. As this may seem to go
against what may typically be considered a good choice, in the case of
bending it's actually the best choice overall.
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