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Ultra-Thin Material
An error will occur when the thickness of a material under test is less
than the low limit of the ultrasonic sensor. When necessary, measure the
minimum limit thickness by comparing it with test pieces. When
measuring an ultra-thin material, sometimes errors called "double
refraction" may occur. This results in a displayed measuring reading that is
twice the actual thickness of the material under test. Another error result is
called "pulse envelop or cyclic leap". This results in the measured value
being larger than the actual thickness. To prevent these kinds of errors
repeat the measurement to confirm the results.
Rust, Corrosion, and Pits
Rust and pits on the surface of the object will cause irregular change in
the measured reading. In extreme situations it will even cause no readings
on the display. To avoid errors, orient the sensor's crosstalk interlayer
plate in different directions to take multiple measurements.
Error in Identifying Material
If you calibrate the meter with one material and then measure another
material, an error will occur. Be careful in selecting the correct sound velocity.
Degradation of Probe
The surface of the probe is allyl resin. Over time its roughness will increase
resulting in reduced sensitivity. If it is determined that this is the reason for
the errors, grind the surface with sandpaper or oilstone to make it smooth
again. If the readings are still not stable, the sensor must be replaced.
Overlapped Material and Compound Material
It is impossible to measure uncoupled overlapped material because
the ultrasonic wave can't pass through an uncoupled space. Since the
ultrasonic wave can't transmit in a compound material in even speed you
cannot use an ultrasonic thickness-gauge to measure overlapped material
and compound material.
Influence of Metal Surface Oxidation
Some metals can produce a dense oxidation layer on the surface, such
as aluminum. Even though the layer is in close contact with the substrate
and provides no obvious interface, the ultrasonic wave will have different
transmitting speeds in these two materials which will cause an error.
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