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Common terms used in lumens

Time:2015-12-29 Views:1663 Compile:SUNPER

Below are some of the reasons as to why lumens are very important when it comes to energy efficiency. In order to understand these reasons better, it is good to first look at the lighting analysis.


Lumen is a unit of luminous flux and thus the overall light output as well as quantity of light can be expressed in lumens. Basically, lumen can be said to be a way of measuring the total amount of visible light in a defined angle or beam when it is being emitted from a light source. Lumen can also be said to be the derived unit of luminous flux which is the total visible light. It is worth noting that luminous flux differs from power in that luminous flux measurements do reflect the varying sensitivity of the human eye to different wavelengths of light. The radiant flux measurements shows the total power of all the electromagnetic waves being emitted and it is independent of the eye’s ability to perceive it.


Common terms used to refer to lumens


There are some terms that are relative to the industry although they are not very important to the typical property owner. One of these terms is LPW lumens. In full this means lumens per watt. It shows the number of lumens produced by the light source for each watt of the electrical power that is supplied to the light source. 

Lumen depreciation refers to the decrease in the lumen output of a light source over a certain period of time. Every lamp type usually has a special lumen depreciation curve which is sometimes referred to as lumen maintenance curve.



An example is that a 400 watt metal halide may depreciates by almost 70 percent within the first three years. A LED high bay fixture may depreciate by 30 percent when used for over 50,000 hours. This is one of the benefits of using the LED lighting. Another term used is lumen maintenance. This is deterioration in the amount of light which is emitted from a lamp over a certain period of time. A lamp having a good lumen maintenance may emit a consistent amount of light during its lifetime. A lamp with poor maintenance may lose up to 50 percent of its ability to emit light.



The most common light sources shows that induction and LED have a longer depreciation curve. Luminaire is a complete lighting unit which contains lamp, housing, ballast and socket components. Luminous efficiency is yet another term used. It is the ratio of the lumens emitted by the luminaire to the total lumens emitted from the light source but within the luminaire. Lux c is a unit of illuminance which is equal one lumen per square meter.


The mean lumen is the average lumen output of a lamp over the rated life. The mean lumen for the HID and fluorescent lamps are measured at 40 percent of their rated lives. The last term is initial lumen. It is the lumens produced by the lamp after the first burn in period which is normally 100 hours.





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