Quantaflex ELTM Design Guide
Useful Life Vs. Half Life
The phosphors which produce the light in an EL lamp are comprised of a special class of doped Zinc Sulfide crystals. As with all Zinc Sulfide phosphors, those in an EL lamp gradually lose their efficiency over time. This loss of efficiency (decay) occurs only during the time the lamp is used. In a properly constructed lamp, using microencapsulated phosphors, there is no decay during normal storage conditions.
The Useful Life of an EL lamp is somewhat subjective and must be determined by taking into consideration the ambient lighting conditions, the end use of the product, the minimum acceptable brightness for the intended use, available power and other factors specific to the application.
The Useful Life of an EL lamp should not be confused with the “Half Life” of the lamp. The Half Life is a period of time of continuous operation which must elapse in order for the brightness to have declined to one half of the initial brightness.
In contrast, the Useful Life of the lamp is that period of time of continuous operation which must elapse before the brightness of the lamp has declined to the point where it is no longer functional in its specific application.
In most EL applications, Useful Life is typically far greater than Half Life. The Useful Life of the lamp can range from a few thousand to as high as 50,000 operational hours.
Correct matching of the lamp, inverter, and the graphics or display are essential to a successful project.
Different colors have different decay characteristics. In all cases, a higher initial brightness results in a steeper decay curve, whereas a lower initial brightness results in a more level decay curve.
The use of “load responsive” inverters can greatly increase the useful life of the EL lamp. As an EL lamp ages, its electrical characteristics change. These changes cause the inverter’s output voltage and frequency to rise, increasing the brightness of the lamp.
Turning an EL lamp on and off has no detrimental effect on its life. Therefore, a duty cycle of 10% “on” time would increase the life of the lamp tenfold.
Contact one of our Representatives for additional information. We will be glad to help specify an inverter for your application. Choosing the right inverter is a critical part of every EL project.