Elcometer NDT PTG6 Mode D'emploi page 13

6 CALIBRATION METHODS
In order for the gauge to make accurate measurements, it must be set
to the correct sound-velocity for the material being measured.
Different types of material have different sound-velocities. For
example, the velocity of sound through steel is 5920m/s
(approximately 0.233in/µs) and the velocity of sound through
aluminium is 6350m/s (approximately 0.248in/µs).
Setting the calibration is crucial for the gauge to function correctly. The
calibration procedure should be performed when the measurement
mode, transducer and / or material type is changed.
A choice of calibration methods is available, see Table 2: Calibration
Methods. To select the calibration method, press Menu/Calibration/Cal
Method.
Calibration
Method
1 Point
2 Point
c
Material
c
Velocity
Factory
Calibration
c
'Material' and 'Velocity' calibration methods are useful when uncoated sample test pieces are not
available.
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TABLE 2: CALIBRATION METHODS
Icon Description
This is the simplest and most commonly used
calibration procedure. A reading is taken and
adjusted on an uncoated sample piece of test
material of a known thickness. Once the
thickness has been entered and confirmed, the
derived sound-velocity is displayed.
This method allows for greater accuracy over
small ranges. Readings are taken and adjusted
on two uncoated sample pieces of test material, of
two different and known thicknesses. Once the
second thickness has been entered and
confirmed, the derived sound-velocity is displayed.
Calibration using the sound-velocity of a material,
selected from a pre-defined list of materials
stored in the gauge.
Calibration using the known sound-velocity of the
material under test.
Calibration using the default factory calibration of
the standard sound-velocity for steel, 5920m/s
(approximately 0.233in/µs).
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