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Incandescent Lamp Life

January 4th Fact-of-the-Day

Miniature and subminiature incandescent lamps are widely used as status indicators and to illuminate tuning dials and meters. They operate in a self-destructive mode that causes failure over time. Furthermore, their filaments can be prematurely damaged by vibration and by cold filament shock when they are switched on. However, there are several ways to extend their life. For example, running them even slightly below their rated voltage significantly extends their life expectancy and makes them much less susceptible to vibration damage. Applying a very small voltage (less than one-percent of rated voltage) while they are switched-off keeps filaments slightly warm and greatly reduces cold filament shock when they are switched on. Incandescent lamps last approximately twice as long running on AC, rather than DC, because DC accelerates grain growth in tungsten filaments that causes earlier development of hot spots. ©2005 Martek International All rights reserved.


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