25
en
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
Mode
Transducer type
required
Notes
High penetration
plastics and
castings
PULSE-ECHO
(P-E)
COATING OFF
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.
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.
Corrosion and
pit detection in
steel and cast
materials
PULSE-ECHO
(P-E)
COATING OFF
Typically a 5MHz trans-
ducer or higher is
required.
Use lower frequencies for greater
penetration and use higher fre-
quencies for better resolution.
Total thickness
of material plus
coatings
PULSE-ECHO
COATING
(PECT)
COATING ON
A special coating style
transducer is required.
There are a variety of coating
transducers in various frequen-
cies available from Elcometer.
Material thick-
ness measured
through a coat-
ing
ECHO-ECHO
(E-E)
THRUPAINT™
Special high damped
transducers are
required; typically the
3.5MHz, 5MHz, and
7.5MHz hi damped
transducers.
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.
