> Thermocouples are not appropriate for that temperature range and
> application, the  cold junction compensation contribution will be
> as much as the thermocouple, you may as well dump the thermocouple
> and stick the compensator down the tube.
>
> > I hope you don't mind too terribly much if I just disagree with you a
> > bit there.  The specifications for the Fluke 80TK thermocouple module
> > seem to belie your opinion about where thermocouples can be used.

I think you are missing the whole point Sphero was making about the
compensation circuit.  Thermocouples are only *relative* measures of
temperature.  This is a bit simplified, but they measure the temperature
difference between one end of the bi-wire cable and the other.  One end is
in the probe, and the other end on a circuit board.  To know the absolute
temperature at the probe, the circuit on the board needs to measure its own
absolute temperature, then "compensate" the thermocouple signal.  Sometimes
this is referred to as an "electronic icepoint".  This is still a win if the
probe is in a flame, oven, or cryogenic chamber where the circuit wouldn't
survive.  In that case small variations introduced by errors in compensating
for the circuit temperature are relatively insignificant, especially in
relative terms compared to a flame temperature.

However, thermocouples lose much of their advantage if you only want to
measure human scale absolute temperatures where circuits survive and operate
nicely.  The circuit has to measure absolute temperature anyway.  At human
temperatures, you can ditch the thermocouple and just measure the absolute
temperature at the probe like you would have had to at the circuit anyway.
This is what Sphero meant by "stick the compensator down the tube", but he
was assuming you understood how thermocouple measuring circuits worked.


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