Accent Lighting
Directional lighting used to highlight particular architectural features, or display items, often using tightly focussed pools of light.
AC
Alternating Current is used in mains electricity supply. It operates at 50 hertz, or 50 cycles per second.
Ambient Lighting
The type of lighting which includes general lighting, and residual daylight, but without particular task or accent lighting.
Amps or Amperes
The unit of measurement for electrical current. In alternating current, Watts (power) = Volts x Amps (current). This is also the unit used for fuse specifications.
Ballast
An electronic device used in fluorescent and discharge lighting, which has the ability to deliver an initially high start-up voltage for firing (with pre-warming if necessary), then smoothly dropping down to a lower operating voltage and current, within the remit of the standard supply voltage and current.
Base
Used to describe the part of the lamp that connects to the electrical supply. Common types are Edison Screw (ES), Small Edison Screws (SES), Bayonet Cap (BC) and Small Bayonet Cap (SBC).
Bayonet Cap
A very common type of lamp base used in domestic lighting; the bayonet cap has two prongs that protrude from the side of the cylindrical lamp base, and lock under the hooked cut out collar within the light fitting.
Beam angle
The concentration of light, measured in degrees or simply described, thrown by lamps or light fittings. Most commonly found on MR type halogen lamps with dichroic reflectors.
Black Light
Often used to describe UV tubes used in disco lighting, due to the type of light emitted. The visible light produced is small, but creates a striking effect on white objects.
Cap: see Base
Capacitor
An electrical device that stores a charge of energy; commonly found within fluorescent ballasts and power factor correction units to regulate light and current output.
Cathode
Cold cathode lamps are fluorescent lamps that operate at a lower temperature, dissipating virtually no heat. A cathode is a type of metal filament that emits electrons into the glass envelope of the lamp, which is filled with a special gas. These negatively charged electrons are attracted to the anode, or positive electrode, generating an electrical current, which subsequently allows light to be created and dispersed.
Coil
Metal windings in a transformer or inductor that surround the metal core, creating a magnetic field and subsequently an electrical charge. Most electric motors feature a coil.
Colour rendering
The ability of a light source to produce a 'true' appearance of colour. Normally daylight is used for comparison, or the colour temperature value.
Colour temperature
Is the temperature in Kelvins that the source produces light at. For example, Cool White, used in some fluorescent tubes, is at 4100 K. Incandescent lamps have a lower colour temperature, which is perceived as warmer, whereas fluorescent lamps have a cooler and therefore higher colour temperature.
Control Gear
Discharge and other specialised types of lamp require control gear to operate. This is usually in the form of starter and ballast, which can be housed internally within the lamp itself, in the luminaire, or externally in another separate enclosure.
Current
The flow of electricity, which is measured in amps or amperes.
Dichroic reflector
Usually found on halogen lamps, a dichroic reflector allows certain regions of the light spectrum to pass through it, reflecting others. This enables the beam that is reflected to be cooler, as most of the heat has been dissipated by the reflector.
Diffuser
A physical device for making light produced by a lamp to be dissipated more evenly, using glass or plastic prisms or lenses. Diffusers are commonly used to make fluorescent tubes less harsh. Some are integral to the luminaire, whilst others are available to buy separately, and in different types.
Dimmable
A light source or lamp that has the ability to be dimmed, that is, the control gear is capable of having its brightness varied reliably. Many fluorescent lights are not capable of being dimmed due to the components used in the ballast.
Dimmer
A light switch that allows the user to vary the intensity of light to a single or group of light fittings, usually by means of reducing the electricity supplied to it.
Direct Lighting
Lighting an area directly, usually straight down onto the required object or area: see Accent Lighting.
Directional Lighting
Where lighting is supplied to an object or area from one direction only.
DMX
Standard control protocol used in disco, theatre and stage lighting.
Edison screw
The type of screw fitting common to GLS light bulbs. Different diameters are available.
Elliptical
Used to describe the shape of the glass envelope in some industrial lighting lamps. The base is usually at one end.
Filament
By passing a current through tungsten wire, or filament, it heats up to such a point that it emits visible light, which can then be used for illumination. Fluorescent lamps have coated filaments which then emit electrons.
Fixture: see Luminaire
Flood
A wide beam angle in a lamp or luminaire, giving light over a wide area.
Floodlight
A luminaire specially designed to provide the maximum beam angle in order to produce light that covers large areas.
Fluorescent Lamp
A type of discharge lamp that converts ultraviolet energy into visible light. The most common types are tubular, but now include low energy lamps, most of which can replace standard domestic type lamps, such as GLS incandescent lamps.
General Lighting
A way of lighting an area so that there is a mostly uniform spread of illumination, without any other specialised lighting.
Glare
An undesirable effect of too much light, particularly when reflected indirectly, which can cause discomfort and irritation.
Globe and Golf Ball
Light bulbs with a spherical shape, rather than tubular or egg-shaped, usually used for decorative lighting. Globes are larger in diameter than golf balls.
GLS or General Lamp Service
A standard term to describe general purpose light bulbs, that is, with no special environmental requirements. Not designed for use in factories or industrial premises, but more for domestic and light commercial use.
High-bay lighting
Luminaires or light fittings designed to light large wide areas, and generally installed high up (25 feet ceilings and higher).
Ignitor
Typically part of the ballast, this piece of lighting control gear supplies an initial high voltage to fire up the lamp. A lower operating voltage is then usually maintained.
Incandescent Lamp
A light source that emits light by way of an electrical current passing through it, until it is white hot, usually a thin tungsten wire.
Indirect Lighting
Used to light an area by not illuminating it directly. Ordinarily this means that lights are positioned in the opposite direction to the area intended to be lit, and uses architectural features like ceilings to bounce the light off. This reflected light produces a diffused, softer feel, which is less harsh than direct lighting.
Infra Red
This specialised form of light source uses the electromagnetic energy in the Infra Red part of the spectrum to produce heat, and a visibly glowing filament.
Instant Start
The ability of some ballasts to warm a lamp to its optimum illumination very quickly. Historically, lamps and ballasts took a long time to warm up, due to the physical process of firing up, whereby lamp filaments needed to be pre-warmed. Nowadays, the high voltage required for an instant start can be supplied by efficient electronic ballasts.
IP or Ingress Protection Rating
The ability of an electrical enclosure (usually on lights) to deal with ingress. It is used to indicate whether an appliance is suitable for use outdoors, bathrooms, or in more specialised environments such as dusty industrial spaces. The first digit denotes protection against solids, the second denotes protection against water or liquid ingress.
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1st Digit - Protection against solid objects |
2nd Digit - Protection against liquids |
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0 No Protection |
0 No protection |
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1 Protected against solid objects greater than 50mm (eg: hands) |
1 Protected against dripping water greater than 50mm DRIPPROOF |
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2 Protected against solid objects greater than 12mm (eg: fingers) |
2 Protected against dripping water when tilted up to 15 |
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3 Protected against solid objects greater than 2.5mm (eg: tools) |
3 Protected against spraying water RAINPROOF |
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4 Protected against solid objects greater than 1.0mm (eg: wires) |
4 Protected against splashing water SPLASHPROOF |
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5 Protected against dust in an amount sufficient to interfere with the satisfactory operation of the equipment |
5 Protected against water jets from any direction JET PROOF |
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6 Totally protected against dust |
6 Protected against heavy seas |
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7 Protected against the effects of immersion between 15 and 100cm |
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8 Protected against long periods of immersion under pressure |
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Kelvin
The standard unit of temperature that operates parallel to the Celsius scale - 273 Kelvin is equivalent 0 C. Kelvins are used in measuring colour temperatures of lamp output.
Kilowatt (kW)
Used in measuring electrical power - 1000 watts equals 1 kilowatt.
Kilowatt hour
The standard unit for electrical billing that measures how long electrical devices or lamps take to burn one kilowatt. Low energy units take longer to burn one kilowatt.
Lamp
An all-encompassing term for a device that produces usable visible light and can be used as a light source.
Lamp life
An average value of the life and usability of a lamp.
LED or Light Emitting Diode
A special type of electronic component increasingly used as an alternative low energy lighting source. It works by converting electrical impulses into light, using a tiny amount of energy and wasting virtually nothing in heat. Individually they are tiny, but can be grouped together to produce bright light.
Lens
Usually made of glass or plastic, a lens is a way of controlling the rays of a light source, by concentrating and focusing them, or by reflecting and dissipating them.
Louvres
Most commonly found in four tube recessed fluorescent fittings, louvres are arrangements of reflective baffles that direct the light in a more efficient way, to provide, for example, good discreet lighting in office areas. Category 2 louvres are specially designed for use in areas with VDUs and computer monitors, to minimise glare from these screens by reflecting the light down at a better angle.
Luminaire
A way of describing a complete light fitting or fixture, which includes the housing, lamp base, and any reflectors and/or lenses, to distribute the light in the way it is designed for.
Normal Power Factor
Normal power factor applies to ballasts with a power factor less than 0.90, and without any power factor correction.
PAR (Parabolic Aluminized Reflector) Lamp
A PAR lamp is usually an incandescent lamp with a curved reflector in one sealed beam unit. It produces an intense, oval beam of light with soft edges. This is created by the lens' prisms and by the reflector. They are available in a variety of different beam angles, e.g. flood or spot.
Pin base
A type of lamp base that uses pins to create the electrical connection. Common types are two pin and four pin. The lamp holder for these lamp bases is usually a sprung ceramic type, which gives effective insulation between the pins. Distance between the pins varies according to the lamp type.
PIR
Passive Infrared sensors, or PIRs, are electronic components used to measure the difference in infrared heat in one place, which means they are effective as motion detectors. They are used in security devices for just that. Being passive means they simply detect, rather than emit any light of their own.
Power
The rate of energy used by a load, for example a heater, expressed in watts.
Power factor
The power factor term is usually applied to motors and fluorescent lamps with in-built components, which make the voltage and current waveforms lead or lag by way of capacitance or inductance. When these waves are in sync, the power factor is said to be unity or one. With large quantities of fluorescent lamps, it is possible to buy power factor correction devices that rectify the lead or lag, which improves efficiency.
Reflector
A device that reflects the light from a light source or lamp. This can be incorporated either into the light fitting itself, or within the lamp.
Screw: see Edison Screw
Spot
A term used to describe a lamp or luminaire beam that is tight and focussed, producing a small bright beam of light.
Starter
An electronic device that delivers a high voltage charge, used to initially fire up a fluorescent or discharge lamp.
Supplementary Lighting
Lighting that is additional to general lighting, for example Task Lighting, or simply used for decorative purposes.
Task lighting
Additional lighting for close up work in a particular area, for example, a reading light.
Tubular
The shape of glass envelope used in some discharge lamps that is long and thin, like a tube, as opposed to elliptical, or egg shape. The base is normally at one end.
Volt
The standard unit of electrical voltage, or the potential difference, across two conductors.
Voltage
Voltage is the term used to describe the potential electrical difference across two conductors. The greater the potential difference, the higher the voltage.
Watt
The standard unit for measuring electrical power.