中文摘要：

HLD—PE—II型普朗克常数测定仪在实际操作过程中会出现很多问题，如高压汞灯关闭后不能立即点亮，汞灯供电的电源设计不完善，使用时其中的稳压模块非常容易烧坏等。把汞灯源换成LED对该仪器进行改进就可以解决这些问题，并具有功耗小、寿命长、性能稳定等优点。

英文摘要：

There are a lot of problems in using the HLD--PE--II planch constant instrument, such as the closed high pressu- er mercury lamp can not been opened immediately. Lamp power supply design is not perfect, so the voltage regulator module is very easy to burn out. If we change the mercury lamp into LED, the problems can been solved. Moreover, the LED light have the advantages of less power consumption, long life, and stable.