Dakota Ultrasonics PX-7 - Manual (Page 27)

PX-7 Ultrasonic Thickness Gauge
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Higher frequency ultrasound is absorbed and scattered more than
ultrasound of a lower frequency. While it may seem that using a lower
frequency transducer might be better in every instance, low frequencies
are less directional than high frequencies.
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Geometry of the Transducer
The physical constraints of the measuring environment sometimes
determine a transducer's suitability for a given job. Some transducers
may simply be too large to be used in tightly confined areas. Also, the
surface area available for contacting with the transducer may be limited,
requiring the use of a transducer with a small cone tipped delay line.
Measuring on a curved surface, may require the use of a transducer
with a matching curved wearface.
•
Temperature of the Material
When it is necessary to measure on surfaces that are exceedingly
hot, special delay lines may be neccessary. Additionally, care must be
taken when performing a "Calibration to Known Thickness" with a high
temperature application. See Appendix B for more information on
measuring materials with a high temperatures.
Selection of the proper transducer is often a matter of tradeoffs
between various characteristics. It may be necessary to experiment
with a variety of transducers in order to find one that works well for a
given job. Dakota Ultrasonics can provide assistance in choosing a
transducer, and offers a broad selection of transducers for evaluation in
specialized applications.