Are You a Thermostat or Thermometer?

While these two temperature-related instruments may be easy to confuse, they’re actually surprisingly different. Thermometers can report the current temperature with remarkable precision. Your shiny new digital thermometer will ensure you know that your family room is exactly 69.3 degrees. Or if your five year old daughter seems warm, it will only take a couple seconds to know how high her fever is with that handheld device you snagged from the drugstore for just $12.

In contrast, a thermostat i...