The principle aim of a luminaire is to control the light emitted by the lamp and to direct it to where it is most needed. It is therefore necessary to accurately measure the spatial distribution of light - a procedure accomplished by a Goniophotometer. The photometer has been designed to handle luminaires up to 1350mm in diameter - so a 1200x600mm fluorescent module can be handled comfortably. In order to meet BS5225 requirements the photoelectric receptor is able to 'look' at the luminaire from every direction in space from a distance of nearly 7metres to achieve the required accuracy.

The purpose designed photometer consists of a rotating lattice arm some 6 metres long and weighing over 300kg carrying 2 large mirrors. Light from the luminaires is reflected from one mirror to the other and then on to the receptor which registers intensity. The arm rotates around the luminaire which is also rotated so that the whole of the light distribution can be scanned.