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Lighting Terminology

Lighting terminology explained

The world of lighting can be a maze of technical terms and abbreviations, so below are some definitions and explanations of the more common terms.

LED

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices but are increasingly used for general lighting. Ideal for colder environments.

Metal Halide Lamp

A high pressure discharge lamp which produces light of a white appearance.

Colour temperature

Colour temperature is the measurement used to describe whether a light source appears ‘warm’ or ‘cool’ – this is indicated by the correlated colour temperature (CCT). As a rule; the higher the colour temperature, the cooler the appearance – and vice versa. A CCT of 2700 – 3000K signifies a lamp with a warm appearance, generally more suited to use in domestic settings, whereas a cooler lamp may have a CCT of 4000+, more widely used in office and retail applications.

CRI

CRI is an abbreviation for ‘colour-rendering index’ – a 0-100 scale that indicates the ability of a light source to show the colours of objects properly. The higher the CRI, the more accurately the lamp will show colours. A high level of colour accuracy may be important in applications such as retail, exhibition space and restaurants – whereas a lower level of accuracy may be more acceptable in warehousing or street lighting.

Re-strike Time

The length of time it takes for a lamp to return to full brightness.

SON

SON is the commonly used name for a high-pressure sodium lamp - a gas discharge lamp that produces light using sodium in an excited state. Often used for street lighting, SONs produce a yellow light with poor colour rendering – but have the advantage of being very efficient. These lamps often reach around 100 lm/W, with higher-powered 600W versions able to reach an efficacy of 150 lm/W.

kWh

Most commonly known as the billing unit for energy delivered to consumers, the kilowatt-hour (kWh) is a unit of energy – i.e. the amount of power used over a period of time. The kWh is equal to 1,000 watt-hours - that’s what a 1,000W device uses in one hour, or what a 1W device uses in 1,000 hours.

DALI

The Digital Addressable Lighting Interface (DALI) is a protocol for lighting controls and dimming agreed by major manufacturers, set out in the technical standard IEC 62386. The AG-Dali is a working group set up by the manufacturers and institutions to promote DALI technology and applications – members of which can display the DALI trademark on devices that are compliant with the current standard.

Circuit watts

Circuit watts (Wcct) is the number of watts used to power an entire circuit, rather than just a single luminaire.

BREEAM rating

The Building Research Establishment Energy Assessment Method, abbreviated to BREEAM, is the industry’s foremost environmental assessment method and rating system for buildings. BREEAM assessment ratings have been awarded to over 200,000 buildings since the launch of the scheme in 1990. The assessment uses recognised measures of performance to evaluate a building’s design, construction and use - including aspects related to energy and water use, the internal environment (health and well-being), pollution, transport, materials, waste, ecology and management processes.

Lux

Lux is the standard unit of illuminance – measuring how much luminous flux (in lumens) is spread over a given area. In other words lumens measures the “amount” of visible light present, whereas Lux is a measure of the intensity of illumination over a surface. A given amount of light will illuminate an area more dimly if it is spread over a larger area.

PIR

PIR sensors (short for passive infrared) are used to detect objects in their field of view by measuring the infrared light radiating from them. PIR sensors are the primarily used technology in presence and absence detection – for example in automatically activated lighting that turns on or off dependent on the presence of people in a room.

Microwave Detector

A type of motion detector that emits microwaves and looks for a return. When the microwaves come into contact with a moving object, some of the microwave energy is reflected back and that triggers an alarm. Heat, light, sound, or vibration will not set off a microwave detector and therefore they are ideal for extreme environments where typical passive infrared (PIR) motion detectors would be ineffective.

Active Detection

With this lighting is automatically switched ON and OFF automatically

Absence Detection

With this the ON is by manual activation but OFF is automatic.

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