Radiometern

Radiometern, commonly translated as radiometer in English, refers to an instrument designed to measure radiant energy, including its flux, spectral distribution, and irradiance. In practical use the term covers devices that convert incident light or heat into an electrical signal or other readable output, enabling quantitative assessments of light or heat radiation across visible and infrared ranges.

Many radiometern rely on a transduction element such as a thermopile or bolometer. A thermopile radiometer uses the Seebeck effect to generate a voltage proportional to absorbed radiant power; a bolometric radiometer detects the temperature rise in a sensing element caused by absorbed energy. Photodiode and photovoltaic radiometers translate light into electrical current, often with filters or gratings to shape spectral response. Spectroradiometers or radiometric spectrometers extend these concepts to measure spectral power distributions across wavelengths.

Principal quantities include irradiance (power per unit area), radiant flux (total power), radiance, and spectral radiance. Calibration is achieved through traceability to national metrology institutes, using standard sources such as calibrated lamps and blackbody references.

Historical note: devices like the Crookes radiometer popularized the idea that light can exert mechanical action, though the classic vane device primarily demonstrates gas flow and thermal effects rather than a direct photonic thrust. Modern radiometern and spectroradiometers are carefully engineered for stable response and accuracy.

Applications span meteorology, climatology, solar energy assessment, astronomy, and industrial process control. They underpin solar irradiance measurements, lamp and LED testing, and calibration of optical instruments.