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5.4 Measuring cylindrical surface
When measuring cylindrical material, such as pipes, oil tubes, etc., it is
very import
ant to select properly the included angle between the probe’s
crosstalk interlayer plate and the axial line of the material to be measured.
Briefly to say, first couple the probe with the material to be measured,
make the probe’s crosstalk interlayer plate
be perpendicular or parallel to
the axial line of the object, shake the probe vertically along the axial line
of the object, the readouts displayed on screen will change regularly.
Select the min. readout from displayed ones as the accurate thickness of
the object.
The standard for selecting the included angle between the probe’s
crosstalk interlayer plate and the axial line of the object is depending on
the curvature of it. For a pipe with large diameter, the probe’s crosstalk
interlayer plate should be perpendicular to the axial line of the object; for
a pipe with small diameter, one can measure with the probe’s crosstalk
interlayer plate being both parallel and perpendicular to the axial line of
the object, and take the min. readout as the thickness.
5.5 Compound profile
When the material to be measured has a compound profile (such as bend
of a pipe), one can use the way described in 5.4 to measure. The
exception is that one should have two analyses, get two results when the
probe’s crosstalk interlayer pla
te being both parallel and perpendicular to
the axial line of the object, and take the min. readout as the thickness.
5.6 Non-parallel surface
To get a satisfactory ultrasonic response, the other surface of the object
must be parallel to or co-axial with the surface to be measured, otherwise,
it will cause measuring error or even no display.
5.7 Influence of material’s temperature
Both the thickness and transmitting speed of ultrasonic wave are
influenced by temperature. If it has a high requirement on the measuring
accuracy, one can use comparison method by test pieces, i.e., use a test
piece with same material to measure under same temperature, and get
temperature compensation coefficient, and use this coefficient to correct
the actual measurement of the object.
5.8 Material with large attenuation
For some material such as fiber, with porous and coarse particles, they
will cause large scatter and energy attenuation in ultrasonic wave, which
