Väčšina miniatúrnych a subminiatúrnych vákuových lámp NDIR je dimenzovaná na nepretržitú prevádzku 5V, AC. Životnosť lámp sa určuje meraním veľmi veľkej série lámp a zaznamenávaním, keď sa 50 percent lámp nerozsvieti.
Na predĺženie životnosti lampy sa často navrhne vlastný obvod na premenu z nepretržitej na pulznú prevádzku. Pulzovaním lampy (vypínaním a zapínaním) sa skracuje doba, počas ktorej je lampa počas vzorkovania zapnutá, čím sa zvyšuje životnosť lampy.
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.
Druhým je použiť napájanie pri zvyšujúcich sa úrovniach, kým sa nedosiahne špičková / optimálna úroveň svetelného výkonu, nikdy nepoužívať plný výkon naraz.
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.
