Whether simple incandescent lamps, ordinary lamps or special halogen lamps, all require filaments made of dimensionally stable tungsten filaments. It offers increased creep resistance and meets stringent requirements for lifetime, light output, reliability and mechanical robustness.
Tungsten filament emits electrons in the form of thermal dissociation (Thermionization). The energy distribution of electrons is 2 eV, and the work function of tungsten is about 4.5eV. The tungsten filament is a thin wire with a diameter of about 100 μm and bent into a V shape. , the current density is 1.75A/cm2, the diameter of the filament becomes smaller with the evaporation of the tungsten filament during use, and the service life is about 40~80 hours.
In actual work, the service life of the filament can be significantly extended by taking some measures.
1. Accurately center the filament
When installing or replacing a new filament, it is still necessary to check the alignment of the filament. It is best to check the installed filament assembly under a dissecting microscope to see if the filament is centered, otherwise it will easily lead to dim brightness of the filament.
2. Appropriately increase the height of the filament
When the filament is working, it emits an electron beam. The emitted beam current of the filament is related to the heating current of the filament and the height of the filament. The larger the height of the filament, the lower the working temperature at which the filament reaches the saturation point, and the slower the surface of the filament evaporates.
3. Manually adjust the filament current in time
Always observe the saturation degree of the filament. When the filament current is not in the saturated state, manually adjust the filament current appropriately to make the filament in the saturated state. We should generally choose semi-automatic adjustment. Otherwise, when the electron gun is automatically adjusted, the filament current will also be adjusted together and the current is too high for a long time, which greatly consumes the filament and seriously affects the life of the filament.