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8.3Measurements On Materials At High Temperatures
When it is necessary to measure wall thickness on surfaces that are in
excess of 200 °F (100 °C), special-purpose high temperature probes should
be used. These probes are built using special materials and techniques that
allow them to withstand high temperatures without damage. Additionally,
care must be taken when performing a “Probe Zero” or “Calibration To
Known Thickness” using a High Temperature probe.
At such elevated temperatures, it is recommended that the user follow these
procedures:
1. Perform a calibration procedure on a sample of known thickness
(refer to section 6.3) with the material temperature at or near the
temperature that will be encountered during measurement.
2.Remove the probe from the hot surface immediately after a “stable”
reading is displayed. Even though the High Temperature Probes are
constructed using materials which can withstand high temperatures,
the probe can begin to heat up, through thermal expansion and
other effects, adversely affecting the accuracy of the measurement.
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