Cheese thermometers with clips. Tijuana Brass / wikimedia / 2007 / CC BY-SA 3.0
A cheese thermometer (aka dairy thermometer, aka milk thermometer) is used to gauge the temperature of milk when making dairy products such as cheese or yoghurt. There are choices of digital, dial, mercury and alcohol thermometers with various features.
Some people feel that the digital and dial are not as reliable as the alcohol or mercury ones. Mercury ones may only be available as vintage models now.
Typically, cheese thermometers come with a clip to fasten them to the side of a pot to more easily monitor a pot of milk as its temperature is being raised. All are or at least should be immersible-safe, as they would of course need to be in case of mishaps; some are even floating.
Temperature ranges that a cheese thermometer will handle vary from 10 C to 205 C (14 F to 400 F).
In making cheese, the temperature ranges between 34 C and 39 C (95 F and 102 F) can be especially critical: 34 C (95 F) will give a very soft curd cheese, 39 C (102 F) will yield a very firm cheese, and each few degrees in between are practically a separate firmness of cheese along the way.