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18.4 TEMPERATURE OF THE MATERIAL
When it is necessary to measure on surfaces that are exceedingly hot, special high-temperature
transducers may be necessary.
18.5 SELECTING THE CORRECT TRANSDUCER
Elcometer NDT has 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 and 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
measured
High penetration
PULSE-ECHO
plastics
and
(P-E)
castings
COATING OFF
Corrosion
and
PULSE-ECHO
pit detection in
(P-E)
steel and cast
COATING OFF
materials
Total thickness
PULSE-ECHO
of material plus
COATING
coatings
(PECT)
COATING ON
Material thick-
ECHO-ECHO
ness measured
(E-E)
through a coat-
THRUPAINT™
ing
25
Transducer type
Mode
required
Cast iron - 1MHz to
5MHz transducer.
Cast aluminium -
10MHz transducer.
Plastics typically require
lower frequency trans-
ducers depending on
the thickness and
make-up of the mate-
rial.
Typically a 5MHz trans-
ducer or higher is
required.
A special coating style
transducer is required.
Special high damped
transducers are
required; typically the
3.5MHz, 5MHz, and
7.5MHz hi damped
transducers.
Notes
Your gauge has been optimised
for cast materials.
Larger diameters offer greater
penetration power because of the
crystal size, for difficult to meas-
ure materials.
Use lower frequencies for greater
penetration and use higher fre-
quencies for better resolution.
There are a variety of coating
transducers in various frequen-
cies available from Elcometer.
These transducers are suitable
for use in both pulse-echo and
echo-echo modes. This enables
you to measure overall material
thickness using the
THRUPAINT™ mode, and then
switch to pit detection mode
(COATING OFF) without chang-
ing transducers.
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