An infrared thermometer is a thermometer which infers temperature from a portion of the thermal radiation sometimes called black-body radiation emitted by the object being measured. They are sometimes called laser thermometers as a laser is used to help aim the thermometer, or non-contact thermometers or temperature guns, to describe the device's ability to measure temperature from a distance. By knowing the amount of infrared energy emitted by the object and its emissivity, the object's temperature can often be determined within a certain range of its actual temperature. Infrared thermometers are a subset of devices known as "thermal radiation thermometers".
An infrared thermometer
A sailor checking the temperature of a ventilation system
IR thermometer checking a person's temperature
A thermometer is a device that measures temperature or temperature gradient. A thermometer has two important elements: (1) a temperature sensor in which some change occurs with a change in temperature; and (2) some means of converting this change into a numerical value. Thermometers are widely used in technology and industry to monitor processes, in meteorology, in medicine, and in scientific research.
Mercury thermometer (mercury-in-glass thermometer) for measurement of room temperature.
Fifty-degree thermometers from the mid-17th century on exhibit at the Museo Galileo with black dots representing single degrees and white represented 10-degree increments; used to measure atmospheric temperatures
A medical mercury-in-glass maximum thermometer.
An alcohol thermometer.