Abstract: A circuit screening system including a target circuit under test receiving a first testing signal in a first period and a second testing signal in a second period; and a clock generating circuit providing a clock signal to the target circuit under test, the clock signal triggering the target circuit under test to receive the first testing signal in the first period and the second testing signal in the second period; the clock signal having a first profile and a second profile in the first period and the second period, respectively, and the first profile and the second profile having a phase difference.

Abstract: An ultraviolet lamp for water sterilization in accordance with the present invention comprises an illuminating unit, a base, an O-ring, a collar and a quartz tube. By clamping the O-ring between the base and the collar to provide a compressing sealing efficiency, water-tightness efficiency is improved and change convenience of the illuminating unit is obtained. Wherein, the illuminating unit is composed of an upper filament and a lower filament enclosed inside a quartz inner tube and then further protected by the O-ring so that a dual-protection to the illuminating unit is achieved. Thereby, the ultraviolet lamp has excellent water-tightness efficiency to extend its lifespan and is convenient and time-saving in assembly and repair.