A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements: the temperature sensor (e.g. the bulb on a mercury-in-glass thermometer) in which some physical change occurs with temperature, plus some means of converting this physical change into a numerical value (e.g. the visible scale that is marked on a red liquid-in-glass thermometer).
Sper Scientific offers Pocket, Partial Immersion, Total Immersion, and Taper Joint thermometers.