Remarks On Application; Measuring Hot Surfaces - sauter TU-US Instruction Manual

9.2 Remarks on application

9.2.1 Measuring tubes and hose material
If a piece of pipe is measured to determine the thickness of the pipe wall, the
positioning of the measuring probe is important. If the diameter of the pipe is larger
than
4 inches, the position of the probe on the pipe should be such that the incision on the
contact surface is perpendicular to the long axis of the pipe.
For smaller pipe diameters, two measurements should be taken at the same point, one
with the incision on the contact surface perpendicular to the long axis and the other
parallel to it. The smaller of these two measurements is then taken as the exact
measurement of this point.

9.3 Measuring hot surfaces

The speed of sound through a particular material depends on its temperature. With
rising...
the temperature, the speed of sound decreases.
For most applications with a surface temperature of less than 100°C no further
precautions need to be taken. At temperatures above this, the change in the sound
velocity of the material to be measured begins to have a noticeable effect on the
ultrasonic measurement.
At such high temperatures, it is recommended to first calibrate with a material sample
of known material thickness, which corresponds exactly or approximately to the
temperature of the material to be measured. This enables the measuring instrument to
calculate the exact sound velocity through the hot material.
For measurements on hot surfaces it may also be necessary to use a "high
temperature probe". These are specially designed for use at high temperatures,
especially since contact with the material surface should be maintained for a short time
to ensure a stable measurement.
While the measuring probe is in direct contact with the hot surface, it heats up. Thermal
expansion and other effects can have a negative effect on the measuring accuracy.
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