Patent ID: 8441215

Claim:
A method for operating one or more high intensity discharge (HID) lamps of a particular type and rating, and having a defined operating life, at a predetermined substantially constant luminous flux output, the method including the steps of: (i) using a test lamp of a similar type and rating to the HID lamps to develop a power-time characteristic that defines the power required at different times in the operating life of the HID lamps to operate the HID lamps at the predetermined luminous flux output, and (ii) operating the HID lamps in accordance with the power-time characteristic, wherein using a test lamp to develop a power-time characteristic includes the steps of: (a) at a plurality of different times in the operating life of the test lamp: (i) measuring a luminous flux output from the test lamp, and (b) if the luminous flux output differs from the predetermined luminous flux, (ii) altering power to the test lamp until its luminous flux output equals the predetermined luminous flux, and (iii) recording the time of alteration and the amount of power required at that time, whereby to develop the power-time characteristic.