There are a number of considerations that need to be made beforehand.

What is the temperature range of your process? How large is the target and how far away is it from the sensor? What type of material are you measuring? Do you require continuous monitoring, or only periodic spot checks? These are the main questions to ask yourself in order to identify the right IR temperature sensor for your application.

Operating conditions, for example ambient temperatures, determine other sensor specifications such as the need for protective accessories, for example built-in water cooling, or the type of display and output capability required. Some IR thermometers have a built-in laser for target sighting, which is especially helpful for marking small targets in dark or inaccessible areas. The measurement target should be larger than the field of view by at least 50percent. If the target is smaller than the field of view, background objects will influence the temperature reading. A two-colour duo-wavelength or ratio instrument is most effective when the target is very small, obscured by smoke or dust, or is moving in or out of the field of view. Single wavelength sensors require a direct line of sight between the instrument and the target. A fibre optic unit, whose cable can snake around obstructions, is best if a direct line of sight between the instrument and the target is otherwise impossible.

The material's emissivity also determines the type of IR sensor required for the job. Emissivity refers to the wavelength at which a material emits IR energy. Most organic, painted or oxidised surfaces have values close to 0.95, which is pre-set in most instruments. Other materials, for example glass, metals, and thin film plastics, have other values, meaning that they emit infrared radiation at different wavelengths. You can find the emissivity of many frequently used materials in an emissivity table, which helps you find the right wavelength range for a given material, and, so, the right measuring device. A sensor with adjustable emissivity allows you to set this value accordingly.

Last but not least, data presentation is an important feature to think about. Some sensors show the temperature as a simple LED reading on the instrument panel, others pass the data to a PC for temperature trend analysis and documentation. With these considerations in mind, you are on your way to finding the right IR thermometer for the job.