Dakota Ultrasonics MMX-7 - Manual (Page 30)

Dakota Ultrasonics
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Thru coating measurements require special high damped transducers. The most
common transducers are the 3.5, 5, and 7.5MHz hi damped transducers. These
transducers are suitable for use in both pulse-echo and echo-echo modes. This
conveniently enables the user to accurately measure overall material thickness using
the thru Coating mode, and then conveniently switch to pit detection mode without
changing transducers. The ¼” 5MHz Hi damped transducer is the most commonly
used transducer for standard thru coating applications.
Thin materials
Use pulse echo mode and a high frequency transducer for these types of
applications. The most common transducers are the 7.5MHz and 10MHz models
with extra resolution. The higher frequencies provide greater resolution and a lower
minimum thickness rating overall.
High temperature
Use and select a special 2.25MHz and 5 MHz High temperature transducer for these
types of applications. Both pulse-echo and echo -echo modes will also work for these
applications. However, echo-echo mode will eliminate error caused by temperature
variations in the delay line of the transducer.
Noisy Material
Materials such as titanium, stainless steel, and aluminum may have inherent surface
noise issues. This is a signal that appears at the surface of the material when using
a dual element delay line probe. Select a higher frequency transducer to reduce this
noise – 7.5MHz and higher for better resolution.
Restricted access
In order to measure materials with lots of curvature or restricted access, use and
select higher frequencies with smaller diameters. The smallest diameter uses 3/16”
crystals with a contact area of .250”.