A maioria das lâmpadas de vácuo miniaturas e sub-miniaturas NDIR são classificadas para 5V, AC, operação contínua. As classificações de vida útil das lâmpadas são determinadas medindo-se um lote muito grande de lâmpadas e registrando-se quando 50% das lâmpadas não acendem.
Muitas vezes, para prolongar a vida útil da lâmpada, um circuito personalizado será projetado para converter de operação contínua para operação pulsada. Ao pulsar a lâmpada (desligando e ligando), a quantidade de tempo que a lâmpada fica ligada durante a amostragem é reduzida, aumentando assim a vida útil da lâmpada.
However simply pulsing the lamp without insuring proper design to protect from inrush current can actually cause premature failure. When the filament is cold and has much lower resistance, thermal shock can cause a fracture in the filament. This happens when power is applied and there is a surge of current which causes rapid expansion of the tungsten, along with thermal shock. Over time, the filament becomes thinner and more brittle and eventually experiences premature failure due to in rush current damage.
When designing the lamp power circuit there are a few commonly used methods to prevent damage from inrush current. The first is called simmer voltage. When using simmer voltage, a small amount of power is supplied to the lamp in the off cycle; typically just enough to keep the filament warm and reduce the impact of inrush current.
A segunda é aplicar potência em níveis crescentes até que o pico/nível ideal de saída de luz seja alcançado, nunca aplicando a potência total de uma só vez.
And the third is to add a circuit that prevents the lamp from drawing additional current, or restricts the amount of additional current that can be drawn at start up.
Life hours is a critical factor when selecting an NDIR lamp. Understanding all contributing factors that affect a lamp's life, coupled with proper system design can greatly impact the life of both the lamp and the system it is designed into. For more helpful information on NDIR lamps, visit our Technical Notes page here.
