Patent ID: 7619362
Filing Date: 2009-11-17
Classification: G01M

Abstract:
1. A method of detecting a leak in an outer jacket of a metal halide lamp having an arc tube inside the outer jacket and operated by a ballast, the method comprising the steps of: in the ballast, monitoring a first electrical characteristic of the lamp during start of the lamp; and detecting a leak in the outer jacket when the monitored first electrical characteristic deviates from a predetermined value of the first electrical characteristic, wherein the first electrical characteristic is one of (1) V′(E) at a predetermined E, where V′(E) is a derivative of lamp voltage V as a function of cumulative energy E delivered to the ballast since ignition, (2) a value of E at which V′(E) reaches a maximum, (3) V at a predetermined E, (4) a local maximum of V′(E) up to a predetermined E, (5) a global maximum of V′(E), and (6) E required to achieve a predetermined V.