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21.3 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.
21.4 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.
21.5 Selecting the correct transducer
Elcometer 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 (896ºF)
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
The following table gives guidance on the type of transducer required for a range of measurement
tasks:
Material being
Mode
measured
High penetration
PULSE-ECHO
plastics
and
(P-E)
castings
Corrosion and pit
PULSE-ECHO
detection in steel
(P-E)
and
cast
materials
31
Transducer type
required
Cast iron - 1MHz to
5MHz transducer.
Cast aluminium - 10MHz
transducer.
Plastics typically require
lower frequency
transducers depending
on the thickness and
make-up of the material.
Typically a 5MHz
transducer or higher is
required.
Notes
Larger diameters offer greater
penetration power because of the
crystal size, for difficult to
measure materials.
Use lower frequencies for greater
penetration and use higher
frequencies for better resolution.
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