Noncontact infrared temperature sensors absorb ambient infrared (IR) radiation emitted by a heated surface. They are used in a variety of applications where direct temperature measurement is not possible. With noncontact infrared temperature sensors, incoming light is converted to an electric signal that corresponds to a particular temperature. Although many different types of products are available, noncontact infrared temperature sensors can be thought of as belonging to general categories based on design and application. This category criteria attempts to distinguish unpacked devices that can be used as part of a larger sensor from, say, a gauge which can be read by simple examination. Categories for noncontact infrared temperature sensors include sensor elements or chips, sensors or transducers, gauges or indicators, and instruments or meters.
 
Operating specifications for noncontact infrared temperature sensors include technology type and electrical outputs. Common technologies include thermal-based bolometers, thermocouples or thermopiles, pyrometers or pyroelectric devices, and optical pyrometers.  Electrical output options for noncontact infrared temperature sensors include analog current, analog voltage, analog frequency, serial, parallel, other digital, and switch or alarm. Additional operating specifications to consider when selecting noncontact infrared temperature sensors include accuracy, which is specified as a percent or in degrees; and repeatability, which is specified normally as a percentage. Target emissivity, response time, and the ratio of the distance to the target or spot-size are additional considerations.

Common features for noncontact infrared temperature sensors include automatic emissivity adjustment, heat flow or flux adjustment, laser spot aiming or sighting, and battery powered.  A noncontact infrared temperature sensor with heat flow or flux adjustment offers features such as a display in British thermal units (BTUs). These devices are designed for an emissivity from 0.9 to 1.0 (e.g., building materials such as ceramic, concrete, glass, paper, plaster, and stone), and can zero-out to temperature on one side (inside) to get the differential.  Noncontact infrared temperature sensors with laser spot aiming or sighting use a laser to indicate where the measurement is being taken from. This laser is not used to sense temperature, however. Noncontact infrared temperature sensors which feature a higher operating temperature, maximum shock, and maximum vibration are also available.