Pyrometer

Pyrometer is a device for measuring high temperatures from a distance by detecting the thermal radiation emitted by an object. It provides temperature readings without contact, in contrast to thermocouples or RTDs. Pyrometers rely on principles of blackbody radiation and the material’s emissivity to translate radiance into temperature. They are commonly used when objects are extremely hot, moving, hazardous, or inaccessible.

Most pyrometers are non-contact infrared devices, though the term also covers optical or visual pyrometers that compare a glow to a calibrated scale. Modern infrared pyrometers use detectors such as photodiodes or thermopiles to measure spectral radiance in specific wavelength bands and convert it to temperature with an emissivity setting and calibration.

Key factors in measurement include emissivity, target temperature range, spectral band, and field of view. Emissivity, the fraction of energy radiated by a surface, must be known or estimated; errors in emissivity cause temperature errors. Some instruments use dual wavelengths or automatic emissivity compensation to reduce this error. Readings are often traceable to standards such as ITS-90.

Applications span metal processing (steel, aluminum), glass and ceramics production, cement kilns, heat treatment, furnaces, and certain food and pharmaceutical processes. Advantages include fast response, non-contact measurement, and the ability to measure very high temperatures. Limitations include sensitivity to surface properties, reflections, window contamination, atmosphere absorption, and calibration drift.