Dakota-ultrasonics MMX-6 Manuel d'utilisateur télécharger pdf (Page 29)

MMX-6 Ultrasonic Thickness Gauge

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. Thus, a higher frequency

transducer would be a better choice for detecting the exact location of

small pits or flaws in the material being measured.

• 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 wearface. Measuring on

a curved surface, such as an engine cylinder wall, 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, high temperature transducers must be used. These transducers

are built using special materials and techniques that allow them to

withstand high temperatures without damage. Additionally, care must

be taken when performing a "Probe-Zero" or "Calibration to Known

Thickness" with a high temperature transducer. See Appendix B for

more information on measuring materials with a high temperature

transducer.

Selection of the proper transducer is often a matter of tradeoffs

between various characteristics. It may be necessary to experiment

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Dakota-ultrasonics MMX-6 Manuel d'utilisateur Page 29