Lux Review presents lighting terminology explained

Colour temperature

Colour temperature describes whether a light source appears ‘warm’ or ‘cool’ – indicated by the correlated colour temperature (CCT). Lamps with a warm appearance have a CCT of 2700-3000K, while cooler lamps will be 4000K and above. The higher the colour temperature, the ‘cooler’ the appearance.

CRI

Short for colour-rendering index, CRI is the ability of a light source to show the colours of objects as they should be. Lamps with poor colour rendering will distort some colours. It’s on a scale between 0 and 100; the higher the number, the better the colour rendering. CRI only works for approximately white sources, and it’s a bit of a blunt instrument because it doesn’t tell you which colours a light source renders well or badly – it just gives you a single overall figure. In the UK, guidance in the Cibse Code recommends lamps with a CRI of over 80 where accurate colour judgement is required, like in shops or of ces. For inspection and colour matching, a CRI of above 90 is recommended. Researchers at NIST in the US have suggested that the colour-rendering index is less suitable for LED spectra, especially in the way saturated colours such as red and yellow are dealt with. They have proposed an alternative colour quality scale (CQS).

Dali

The Digital Addressable Lighting Interface is a protocol for lighting controls and dimming agreed by major manufacturers. It is 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.

DIN rail

A DIN rail is a metal rail of a standard type widely used for mounting circuit breakers and industrial control equipment inside equipment racks.

HID lamps

Short for high-intensity discharge, HID lamps are a type of electrical gas discharge lamp which produces light by means of an electric arc between tungsten electrodes inside a see-through tube. HID lamps include mercury-vapour, quartz metal-halide, ceramic metal halide, sodium-vapour and xenon short-arc lamps.

kWh

The kilowatt-hour is a unit of energy 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. It’s the unit that your electricity bill is counted in.

Lumen package

The total amount of lumens delivered by a light source.

Lux

Lux is the international unit of illuminance – a measure of how much luminous  ux (in lumens) is spread over a given area (in square metres). In other words, it tells you how much light is arriving on a surface. 1 lm/m2 equals 1 lx.

Mean cylindrical illuminance

Mean cylindrical illuminanceis the mean illuminance over an indefinitely small cylinder placed at the point of interest, usually with the axis of the cylinder vertical. In contrast with mean spherical illuminance, mean cylindrical illuminance depends on the direction of the light.

PIR

Short for passive infrared. PIR sensors are electronic sensors that measure infrared light radiating from objects in their field of view. They can detect heat from objects that is undetectable by humans

Zhaga

Zhaga (not an acronym) is an industy-wide cooperation to standardise specifications for the interfaces of LED light engines. The aim is to enable interchangeability between products made by diverse manufacturers by defining interfaces for a variety of application-specific light engines. Currently, the membership of Zhaga comprises manufacturers only.

ZigBee

ZigBee is a global specification for digital radio communication that is suitable for applications that require a low data rate, long battery life, and secure networks. Among those application is lighting control. No special devices are needed to connect equipment to the lighting network. ZigBee is simpler and cheaper to implement than other wireless networks, such as Bluetooth.

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