S. Traberg-Borup
Being able to compare various luminaires experiments have been made with photon flux density and light distribution from luminaires. The luminaires were provided with 400 Watt, 150 Watt and 70 Watt high-pressure sodium lamps, respectively. Each luminaire has been examined at a mounting height between 1.0 and 2.0 metres.

Concerning the light distribution the results are comparable to some extent with the data given by the manufacturers. The examinations have made it possible to calculate a specific factor for the particular luminaire. The factor is used in the calculation of the photon flux density reaching the plants.

Normally, the manufacturers are showing the light distribution at a relative iso-lux/diagram, but now it is also possible to show it at a relative iso-PAR diagram using μE/sec m2 or μmol/sec m2 as the base unit (PAR - Photosynthetically Active Radiation in the waveband 400 – 700 nm).

As the flux from the high-pressure sodium lamps varies with the mains voltage, an examination was made altering the voltage between 200 and 240 volts in 5 volts intervals. The result showed that the flux was doubled when the voltage was altered 40 volts.

Traberg-Borup, S. (1989). LIGHT DISTRIBUTION FROM LUMINAIRES IN GREENHOUSES. Acta Hortic. 245, 505-511
DOI: 10.17660/ActaHortic.1989.245.68

Acta Horticulturae