constant light output (CLO)

In streetlight Central Management Software (CMS) applications, the adjustment of light to allow for degradation in brightness due to the age of the lamp.

The adjustment takes place using a lumen deprecation curve, which specifies how much the lamp should be dimmed. This is calculated in hours as a percentage of the dimming level set by configuration or by the schedule based on the lamp age.

The CLO algorithm takes into account the age of the bulb or lighting element. As the element ages, it deteriorates, emitting less light for a given input level. When the element is brand new, the NIC firmware sends a lower value to the control board. As the light ages, the value sent gradually increases. When the light is fully depreciated, firmware does not reduce the CMS requested value. The amount of reduction is defined by a depreciation curve, which defines the reduction factor at various ages of the bulb.