I'm going to back Andy M. up on this one skilletlicker - there are different kinds of thermometers used, and intended to be used, in different ways.
An oven thermometer is intended to tell you the ambient temperature of the air in the oven. These are generally analog dial
/spring or stick/bulb types and either sit on or hang from an oven rack. They are generally inexpensive.
There are instant read thermometers that you stick into the meat to check the temp (these can be analog or digital) but are not intended to be left in the meat and/or oven during cooking. Taylor makes them ranging from about $5 - $15 - and are slower than the Thermapen which costs about $70-$100+ (depending on model and where you buy them).
Meat thermometers are intended to stay in the meat during the cooking process ... and come in 3 flavors - analog dial
, and the new "probe" models where a rigid metal probe with the sensing element in the end of the tip is attached by a wire to a digital readout that remains outside the oven. This is like the old dial and bulb type meat thermometers - the sensing portion is in the tip of the probe so what you are reading is the temp at the tip of the probe - not the ambient air in the oven. These are not intended to be "instant" or "rapid" read.
There are also fry/candy thermometers that generally go a little
higher than meat thermometers - but are longer and also have a way to clip them to the pot, something that meat thermometers don't have.
I have a Taylor bulb-type oven thermometer
, a Taylor bulb-type candy/fry
thermometer, both analog
instant reads made by Taylor, and a probe model made by Taylor
which is almost identical to the comperable Polder
which I picked up at Target for about $16 (they still offer it but it is now labeled as TruTemp
- only the colors of the buttons are different).
Dial thermometers depend on a spring made of flat wire that will expand as it heats up, which turns the dial - something like a thermostat works to control your heater/AC. Bulb thermometers depend on the liquid expanding as heated and is moved up the column. Digital uses a method "something" like the dial but is more accurate since they measure changes in electrical conductivity instead of just spring swelling/shrinking.
EDIT: Seems we were typing at the same time ...
I will agree that the "max temp" of the cord on the probe does vary somewhat between brands/models. While the ones intended for indoor oven use are ginerally in the 350F-400F range ... the more expensive "BBQ" rated models appear to go up to 450F-500F ... but they are more expensive and above the temps I would want to use for good BBQ.