Dakota-ultrasonics PR-82 Manuel d'utilisateur télécharger pdf (Page 22)

Dakota Ultrasonics

TRANSDUCER SELECTION

The PR-8

is inherently capable of performing measurements on a wide

range of materials, from various metals to glass and plastics. Different

types of material, however, will require the use of different transducers.

Choosing the correct transducer for a job is critical to being able to easily

perform accurate and reliable measurements. The following paragraphs

highlight the important properties of transducers, which should be

considered when selecting a transducer for a specific job.

Generally speaking, the best transducer for a job is one that sends

sufficient ultrasonic energy into the material being measured such that a

strong, stable echo is received by the PR-8

. Several factors affect the

strength of ultrasound as it travels. These are outlined below:

• Initial Signal Strength

The stronger a signal is to begin with, the stronger its return echo

will be. Initial signal strength is largely a factor of the size of the

ultrasound emitter in the transducer. A large emitting area will send

more energy into the material being measured than a small emitting

area. Thus, a so-called "1/2-inch" transducer will emit a stronger signal

than a "1/4-inch" transducer.

• Absorption and Scattering

As ultrasound travels through any material, it is partly absorbed. If

the material through which it travels has any grain structure, the sound

waves will also experience scattering. Both of these effects reduce the

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Dakota-ultrasonics PR-82 Manuel d'utilisateur Page 22