SECTION 5
SOLVING PROBLEMS
5.4 Deformed or Broken Thermocouple
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The thermocouple is well protected while the TC
head is in the instrument. Cleaning procedures
detailed in this manual should not harm the thermo-
couple, but it can be deformed or broken if contact-
ed by any object while it is out of the instrument.
•
If the thermocouple is only slightly deformed,
the instrument will automatically adjust for the
deformed thermocouple and function normally.
•
A badly deformed thermocouple will still function
but will show a noticeable loss of measurement
precision.
•
A deformed or flattened thermocouple with its
bead lying close to or touching the surface of the
mount will not cool to normal temperature
depression during the measurement cycle
(Appendix C). As a result, the instrument may
display a meaningless value.
Restoring a Deformed Thermocouple
You can usually salvage even a severely deformed
thermocouple by carefully lifting it into normal posi-
tion. Although the thermocouple wires are only 0.025
mm in diameter, they are quite malleable and are
generally amenable to straightening and reshaping.
In any event, you may as well make the attempt,
since a badly deformed thermocouple will not func-
tion. Because of the delicate nature of the task, you
will need steady hands and a microscope, preferably
stereoscopic, having magnification in the range of
30X to 60X.
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