Comparison of luminous intensity distributions measured on luminaire turning and mirror goniophotometer

A goniophotometer is needed to measure the luminous intensity distribution of luminaires. Goniophotometer types differ basically how their axes relate to the optical axes of the luminaire under test and in which order they apply the turnings. As the result one gets luminous intensity distributions in different coordinate systems, but those can be transferred into each other's system. Some light source types like gas discharge types based on their operation principle are not allowed to measure them other then in their operation position. There are some light source types which operate independent from their operating positions. Such light sources are for example the semiconductor based light sources, like the LEDs. Some specially designed high power luminaires (like luminaires for sport lighting) can have forbidden operating positions which also are not allowed to measure with luminaire turning goniophotometers. The opinions about the right method are different also inside professional lighting communities. It is often complaint when such measurements are done that the luminaire is operated other than its original burning position and therefore the thermal conditions change inside the luminaire which results false data according the luminous intensity distribution and also its total luminous flux. The comparison is based on measurements carried out both on luminaire turning and mirror goniophotometer. Based on our experience the rotation of an LED luminaire is not causing definitely a worse cooling. To proof this experience thermal sensors are placed and monitored on the luminaires during both types of measurement. The aim of the paper is to show the observed differences on the different luminaire types in their luminous intensity distributions and their total luminous flux values when measured on different goniophotometer types.