A pyrometer, or radiation thermometer, is a type of remote sensing thermometer used to measure the temperature of distant objects. Various forms of pyrometers have historically existed. In the modern usage, it is a device that from a distance determines the temperature of a surface from the amount of the thermal radiation it emits, a process known as pyrometry, a type of radiometry.
An optical pyrometer
A sailor checking the temperature of a ventilation system
Technician measuring the temperature of molten silicon at 2,650 °F (1,450 °C) with a disappearing-filament pyrometer in Czochralski crystal growing equipment at Raytheon transistor plant in 1956
Measuring the combustion temperature of coke in the blast furnace using an optical pyrometer, Fixed Nitrogen Research Laboratory, 1930
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