Fluke DATAPAQ Tracker XL2 User Manual page 36

Thermocouple Cable Insulation
The practical operating temperature of the thermocouple probes is limited by
the cable insulation material's temperature characteristics.
Insulation
Glass fiber, thin
Glass fiber, thick
Mineral insulation (MI)
PTFE
Glass-fiber-insulated probes are available in both thin and thick forms.
Impregnated with a silicone resin binder, thin-glass-fiber-insulated probes are
more robust than thick-glass-fiber-insulated probes; they are suitable for use at
temperatures up to 500°C/932°F. Thick-glass-fiber-insulated probes are more
flexible than thin, being less impregnated with silicone resin; they are more
suitable for oven use, and are capable of continuous operation at temperatures
up to 500°C/932°F, and short-term operation at up to 700°C/1,292°F. They
can be used when probe cables are close to heating elements.
Mineral-insulated (MI) probes have an enclosed junction providing increased
immunity to electrical interference. Less flexible than PTFE or glass fiber, but
suitable for use up to 1,250°C/2,282°F, they can be used when probe cables
may be close to heating elements.
PTFE (polytetrafluoroethylene)-insulated probes are suitable for general-
purpose use at temperatures up to 265°C/509°F. PTFE is a robust, flexible,
non-stick material, with a low thermal mass and therefore a quick response
time. This is the standard insulation for oven use, though it cannot be used
when probe cables may be close to infra-red heating elements.
PTFE does not support combustion, but decomposes above 265°C/509°F
The important products from PTFE thermal decomposition are as follows.
36
Thermocouple Probes
Upper Temperature Limit
500°C/932°F
500°C/932°F continuous, 700°C/1,292°F peak
1,250°C/2,282°F
265°C/509°F
WARNING
producing small amounts of toxic fumes.
OVEN TRACKER XL2