DM4E, DM4, DM4 DL Operating Manual Page 27
6.0 Application Notes
A 100% duty cycle can be employed when taking measure-
ments below 400°F (204°C). No cooling of the probe is re-
quired.
If taking thickness readings at temperatures above 400°F, cool
the probe in air as follows:
• 15 seconds for temperatures from 400°F to 550°F
• 30 to 120 seconds for temperatures from 550°F to 1,000°F
Before taking another reading, carefully remove the remaining
couplant and residue from the probe.
Thickness measurements made at high temperatures must be
corrected for the effect of temperature on the material sound
velocity. Velocity in steel changes at an approximate rate of -
0.5% per 100°F (-1.0% per 100°C).
Some applications may exceed the instrument’s capabilities.
If high temperature measurements are unsatisfactory after sev-
eral attempts using this procedure, better results may be
achieved by using a high temperature probe with an ultrasonic
flaw detection instrument.
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