Characterization of acoustic resonances in HID lamps based on relative impedance difference with an automated measuring station

In the development of high luminance, high efficacy HID lighting systems and the optimization of electronic ballasts, lamp parameters related to acoustic resonances have to be known. A measurement procedure detecting acoustic resonances in HID lamps based on the lamppsilas impedance is presented. The impedance comes with the advantage of a high sensitivity to changes in the lamp and is well suited for automation. In contrast to existing measurement procedures, the excitation signal is continuously turned on and off during the measurement, leading to a high repeatability. The procedure is illustrated by measurement results on 30 and 35 W automotive short-arc HID lamps. In addition, a measurement setup - including hardware and software details - based on the presented procedure is described.