© Denzil Green
Oven Safe Thermometers can be dial or digital.
The dial ones work by “coil” action. Inside the skewer bit, there is a metal coil that expands when heated, which makes the dial move. Where it reads the temperature on the skewer part is generally from the tip upwards to about 2 to 2 1/2 inches (5 to 6 cm.) Though the temperature inside the meat along those inches being measured may vary somewhat, what you see on the dial is an average of the range.
If you forget to put an oven one in, and need to get the temperature, put it in, and wait at least two minutes to get a reading. Some people prefer this type because they go in and stay in, negating the need to poke the meat any more than necessary in order not to let juices out (though they could always just instant-read poke it in the same place each time.)
You can also get microwave oven safe ones. Some microwaves come now with a built-in probe.