Pyrometer

Pyrometers measure temperature without physical contact by detecting the infrared or visible radiation emitted by an object. Types include infrared (IR) pyrometers (which measure broadband or narrow-band infrared radiation), optical pyrometers (which compare the brightness of the target to an internal reference), and ratio pyrometers (which use the ratio of radiation at two wavelengths to reduce emissivity sensitivity). They are essential for measuring extremely high temperatures (molten metals, furnaces, kilns), moving objects (rotating parts, conveyor products), or electrically sensitive targets.

Calibration of pyrometers involves using blackbody radiation sources — precision furnaces with a calibrated cavity that closely approximates a theoretical blackbody (emissivity near 1.0). The pyrometer is aimed at the blackbody source set to known temperatures, and the pyrometer's readings are compared. Calibration must account for the optical path (window transmission, atmospheric absorption) and the emissivity setting. Some pyrometers also require calibration of the distance-to-spot ratio (D:S), which defines the measurement area at a given distance.

For calibration management, pyrometers require attention to several unique factors. Emissivity — the property of the target surface that determines how much radiation it emits compared to a blackbody — is the largest source of error in pyrometry. Users must understand the emissivity of their target materials and set the pyrometer accordingly. Lens contamination, ambient temperature changes, and background radiation can also affect accuracy. Calibration intervals are typically 12 months, with periodic verification using a portable blackbody or by comparison with a contact thermometer where feasible.