This is bad practice ! (and it is not a small point). Often "thermocouple" is used generically.
Thermocouples are NOT adequate for this kind of measurement, in the long term. They are cheaper but degrade too easily. For reliable measurement of hydrogen at higher temps - you should use RTDs. They are more expensive but can be exposed to almost anything and maintain accuracy. Typically RTDs are platinum on the exterior. See the Wiki entry. * * This is a standard industrial technique, though it is slower to respond than having the thermocouple exposed directly to the hydrogen in the reactor.
