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11.8 Abnormal reading
Operators should have the ability of identifying abnormal readings. Usually, rusty sports, corroded
pits and the interior flaws of the test materials can all cause abnormal readings. For solution, see
chapter 10 of this manual.
11.9 Use and choice of coupling agents
Coupling agent is used for transmitting high frequency ultrasonic energy between the probe and
the test material. Incorrect selection of the types of coupling agents or improper usage may cause
errors or flashing of the coupling sign, making it unable to measure the thickness. Coupling agent
should be used in proper amount and coated evenly.
It is important to select the proper type of coupling agents. When the surface of the test material is
smooth, low viscosity coupling agent should be used (coupling agents and light machine oil are
provided with the instrument). High viscosity coupling agents (such as glycerin paste and
lubricating fat
，
etc.) may be chosen for rough surface or vertical surface or peak surface.
11.10 Protective sheath of probe
When measuring curved surface, curved surface probe sheath should be used so as to gauge the
thickness more accurately. Probe protective sheath is optional in purchasing.
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12. Precautions
12.1 Cleaning of test blocks
As the correction of the instrument by using the test block provided needs coupling agents, it is
necessary to take measures against rusting. After usage, the test blocks must be cleaned. When the
temperature is high, caution must be taken not to stain it with sweat. When not used for a long
time, the test block should be coated with a thin layer of fat to prevent rusting. To use again, clean
the fat, the instrument will work normally.
12.2 Cleaning of the shell of the instrument
The shell of the instrument should be cleaned with a little amount of clean water instead of
alcohol or dilution liquid which are corrosive to the shell, especially the window.
12.3 Protection of the probe
The surface of the probe is made of acrylic resin, sensitive to rough surface. It must be handled
gently. When measuring rough surface, the sliding of the probe over the surface should be
prevented as far as possible.
At the ambient condition, the temperature of the test surface should not exceed 60
C. Otherwise,
the probe cannot be used any more.
The collection of grease and dust will make the probe wire aging fast or fracture. After usage,
please clean the cable.
