What is a conductive temperature probe called? They're relatively massy metal rods (5-8mm thick, 5-15cm long) that have a single conductor (NOT 2 conductor wire) to connect to the thermostat.
The connecting conductor wire is reasonably thick to (presumably) conduct the heat effectively to the measuring device.
I replaced one in my oven, and my spa has one too.
(I ask, because I broke the wire on my spa one, and searching the internet without a technical continually brings up thermo couples and other sensors)
Updated to help others: I'm looking at something like this is the sort of thing: