Glossary of Terms

Amperes (Amps)
A measure of electrical current. Amps = Watts/Voltage
Average Rated Life
An average rating, in hours, indicating when 50% of a large group of lamps have failed, when operated at nominal lamp voltage and current. Manufacturers use 3 hours per start for fluorescent lamps and 10 hours per start for HID lamps when performing lamp life testing procedures. The life of an LED is defined as the operating time in hours for the lamp to reach L70 which designates 70% lumen maintenance (or 30% reduction in initial light output). Every lamp type has a unique mortality curve that depicts its average rated life.
Color Temperature
A numerical measurement of the color appearance of a light source measured in degrees Kelvin (K). It also refers to the way color groups are perceived (psychological impact of lighting) with "warm" colors at the red/orange/yellow end of the spectrum and "cool" colors at the blue end.
A measure of the rate of flow of electricity, expressed in amperes (A).
An LED driver is a self-contained power supply that has outputs which match the electrical characteristics of the LEDs. Drivers should be current-regulated and may also offer dimming by means of pulse width modulation (PWM) circuits.
High Power LED
An LED that can be powered at hundreds of milliamps (mA) in contrast to "traditional" indicator LEDs (SMD, 8mm, 5mm, etc.) which can only be powered at a few milliamps. A High Power LED produces high lumen output and can be set in an array to form a powerful LED lamp.
Light arriving at a surface, expressed in lumens per unit area; 1 lumen per square foot equals 1 footcandle, while 1 lumen per square meter equals 1 lux.
Initial Lumens
The measured luminous output of a new light source.
Instant Start
A type of fluorescent lamp-ballast circuit designed to start fluorescent lamps as soon as the power is applied. Originally, instant-start circuits were developed to eliminate separate mechanical starter devices. Slimline fluorescents lamps operate only on instant circuits.
Lumen (lm)
A measure of luminous flux or quantity of light emitted by a source.
Lumen Depreciation
The gradual decline in light output from a light source over time due to filament deterioration and bulb darkening.
Lumen Maintenance
A measurement of how a lamp maintains its light output over time.
Lumen Per Watt (LPW)
A measure of the efficacy (efficiency) of a light source. The number is achieved by dividing lumens produced by watts consumed.
Luminous Efficacy
The light output (lumens) of a light source divided by the total power input (watts) to that source. It is expressed in lumens per watt.
Lux (lx)
A unit of illuminance or light falling onto a surface. One lux is equal to one lumen per square meter.
Rated Lamp Life
The length of time of a statistically large sample between first use and the point when 50% of lamps died.
Surface Mounted Device (SMD)
Specific style of miniature LEDs. The LED chip is mounted directly to the surface of a circuit board. Often referred to as the "honeycomb" LEDs.
A measurement of the electromotive force in an electrical circuit or device expressed in volts.
A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy.