PARsensorer

PARsensorer are instruments used to measure photosynthetically active radiation, the portion of the light spectrum roughly from 400 to 700 nm that drives photosynthesis. In practice, PAR is often expressed as photosynthetic photon flux density (PPFD) in micromoles per square meter per second (µmol m−2 s−1), or as daily light integral (DLI, mol m−2 d−1) when the measurement is integrated over a day.

Most PAR sensors are quantum sensors based on silicon photodiodes with a spectral response matched to the PAR band. They convert incident photons into an electrical signal that is calibrated to PPFD. Many models include temperature compensation and a cosine response to accurately measure light from different sun angles. Some sensors provide digital outputs or are designed to connect to data loggers or meteorological stations.

Common types include quantum sensors, which are optimized for PAR and PPFD, and radiometric or broadband sensors that report irradiance in W m−2. In research and horticulture, PAR sensors are often paired with data loggers and weather stations to monitor light conditions over time, assess daily light sums, and relate light to plant growth or canopy photosynthesis.

Applications span greenhouse and controlled-environment agriculture, field ecology, agronomy, and plant physiology research. They help optimize lighting regimes, validate growth models, and quantify light environment influences on crop yield. Key considerations when selecting a PAR sensor include spectral response accuracy, cosine error, temperature stability, calibration traceability, and compatibility with data logging or remote monitoring systems.