ZX-3
Ultrasonic Thickness Gauge
11
two elements and their delay lines are packaged in a single housing but acoustically
isolated from each other with an insulated sound barrier. This allows the transducer
the ability to achieve very high sensitivity for detecting small defects. Also, the
surface of the test material does not have to be as flat in order to obtain good
measurements.
Dual element transducers are normally used in pulse-echo mode for finding defects,
and in echo-echo mode for through coating measurements.
Dual element delay line transducers are have a usable range of 0.025” and up,
depending on the material, frequency, and diameter.
A limitation of dual element delay-line transducers is the V shaped sound path.
Because the sound travels from one element to another, the time versus thickness
relationship is non-linear. Therefore, a correction table in the instruments software is
used to compensate for this error.
Dual Element Transducer showing V-path of signal
Searching for small defects
Dual element delay line transducers are especially useful in searching for small
defects. In pulse-echo mode with high amplifier gain, very small defects can be
located. As a result, this configuration is commonly used for corrosion inspections.
The dual element style transducer will find wall deterioration, pits, cracks, and any
porosity pockets during tank and pipeline inspections.
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