Couplant - AND AD-3255 Instruction Manual

Suitability of Materials
The measurement of the thickness gage depends upon the sound
wave passing through the material. All materials do not allow sound
waves to penetrate. Ultrasonic thickness measurement can be used
for metal, plastic, glass and multifarious materials. but it can not use
for a part kind of cast iron, concrete, wood, fiberglass "fibre-reinforced
plastic" or some rubber.
Reflection Wave
In measuring of ultrasonic wave thickness in the standard pulse -
echo mode, not the first reflected wave from the bottom face of the
measured object but the second reflected wave may be measured. In
this case, the thickness value is 2 times that of the correct thickness.
Fully understand these phenomena when using this thickness gage.

5-4. Couplant

Function of the Couplant
In order to couple the ultrasonic wave between the transducer and
the material, it is necessary to fill the surface with couplant
"Incompressible fluid." Typical couplants are machine oil, glycerin,
water, and commercial couplant.
Suitable Quantity of the Couplant
In general, apply approximately one drop of the couplant to the
surface.
Error Related to the Couplant
Should the couplant form a bridge-like thread when removing the
transducer from the surface, the measurement value would be
different between the value of placing the transducer on the surface
and the value removing the transducer from the surface.
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