Thermometer

A thermometer measures temperature by detecting a temperature-dependent change in a material or sensor, such as expansion, electrical resistance, or emitted radiation.

Thermal expansion: The increase in a material’s dimensions as its temperature rises. Liquid-in-glass thermometers translate this expansion into movement along a scale.
Temperature: A physical quantity describing the thermal state of matter and the direction of heat flow. A thermometer’s purpose is to assign a value to this quantity.
Clinical thermometer: A thermometer designed to measure human body temperature. Its specialized range and form suit temperature checks in healthcare.
Infrared thermometer: A noncontact instrument that estimates an object’s temperature from its infrared radiation. It contrasts with contact thermometers, which exchange heat with the measured object.
Thermoelectric effect: The production of an electric voltage from a temperature difference between materials. Thermocouples use this voltage to infer temperature.
Celsius: A temperature scale defined by fixed points associated with water’s freezing and boiling under standard pressure. Many everyday thermometers display temperatures on this scale.
Weather station: A facility or instrument suite that records atmospheric conditions, including air temperature. Weather stations use shielded thermometers to measure air rather than direct sunlight.
Liquid-in-glass thermometer: A thermometer that indicates temperature through the expansion of liquid in a sealed glass tube. Its visible column contrasts with electronic thermometers’ sensor-based displays.
Electrical resistance thermometry: Temperature measurement based on the change in a conductor’s electrical resistance. Resistance thermometers convert a calibrated resistance change into a temperature reading.
Kelvin: The SI base unit of temperature, with zero at absolute zero. Scientific thermometers often report measurements in kelvins.

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