Infrared thermometers: what they measure and when to trust them
An IR thermometer measures radiance, not temperature. Emissivity, field of view, distance and reflected background all change the reading — which is why they are for screening, not for GDP records.
Infrared thermometers infer surface temperature from thermal radiation. Every surface radiates according to its temperature and emissivity; the instrument assumes an emissivity (often 0.95) and calculates a temperature. Painted, matte or organic surfaces are near 0.95; bare metals may be 0.1–0.3, and the reading is then dominated by reflected surroundings.
Use in storage and distribution
- Screening a pallet's surface on receipt: fast, non-contact, indicative only.
- Not a substitute for a logger inside the load: surface temperature differs from core.
- Not suitable for air temperature at all.
- Calibration: against a blackbody source or flat-plate calibrator, with the emissivity set as in use.
Frequently asked questions
- Can an IR thermometer verify a cold room is at 2–8 °C?
- No. It reads surface temperature of whatever it is pointed at, affected by emissivity and reflection; a calibrated air sensor is required for the space.
References
- [1]ISO/IEC 17025:2017 — General requirements for the competence of testing and calibration laboratories
General technical guidance written against the cited sources. It is not regulatory or legal advice and does not replace the applicable standard, guideline or a qualified reviewer's judgement.
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