Elcometer CG30 Operating Instructions Manual page 22

15.1 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. Therefore a 6 mm (1/4")
transducer will emit a stronger signal than a 3 mm (1/8") transducer.
15.2 ABSORPTION AND SCATTERING
As ultrasound travels through any material, it is partly absorbed. If the materials through which the
sound travels have any grain structure, the sound waves will experience scattering. Both of these
effects reduce the strength of the waves.
Higher frequency ultrasound is absorbed and scattered more than ultrasound of a lower frequency.
It may seem therefore that using a lower frequency transducer might be better in every instance,
however low frequencies are less directional than high frequencies.
15.3 GEOMETRY OF THE TRANSDUCER
The physical constraints of the measuring environment sometimes determine the suitability of a
transducer for a given job. The transducer may simply be too large to be used in confined areas.
Also, the surface area available for contacting with the transducer may be limited. Measuring on a
curved surface may require the use of a transducer with a matching curved wearface.
15.4 TEMPERATURE OF THE MATERIAL
When it is necessary to measure on surfaces that are exceedingly hot, special high-temperature
transducers may be necessary. Additionally, care must be taken when performing a 'Calibration to
Known Thickness' with a high temperature application - see "Measuring hot surfaces" on page 22.
15.5 SELECTING THE CORRECT TRANSDUCER
Elcometer NDT have a complete range of transducers to meet your requirements, including:
• A range of frequencies and sizes
• Straight and right angle
• Transducers available as potted or microdot transducers:
Potted transducers - transducer cable is permanently fixed to the transducer head.
Microdot transducers - transducer cable is fixed to the transducer head by a connector - allows
transducer heads to be replaced quickly and easily.
• High temperature transducers - temperature up to 480°C (896°F)
When selecting a transducer, it is important to choose one which will best meet your application,
taking into consideration:
• The measurement range
• The type of material to be tested
• The design of the transducer probe type
For full details of the Elcometer NDT range of transducers contact your local Elcometer NDT
supplier, or visit the Elcometer NDT website www.elcometerndt.com
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