Maximum ambient temperature

The maximum ambient temperature for which a compact fluroescent lamp (CFL) product is warranted to achieve rated life.

Maximum ballast case temperature

The maximum temperature of the ballast case for which the manufacturer's life rating is valid.

Maximum relative light output

Illuminance measured at a fixed distance from the lamps.

Mean light output

Light output typically evaluated at 40% of rated lamp life. In combination with initial light output, mean light output may be used to estimate lamp lumen depreciation.

Medium Bi-Pin

A type of connector commonly used on T-8 and T-12 fluorescent lamps. Two small pins protrude from the lamp ends, which are inserted into a socket in the fixture.

Mercury vapor (MV) lamp

A high-intensity discharge lamp type that uses mercury as the primary light-producing element. Mercury vapor lamps produce light with a CCT from 3000 to 7000 K. Mercury vapor lamps with clear outer bulbs have CRI values from 15 to 25, whereas phosphor-coated lamps have CRI values from 40 to 55. Mercury vapor lamps are less efficacious than other HID lamp types, typically producing only 30 to 65 LPW, but they have longer lamp lives and lower initial costs than other HID lamp types.

Metal halide (MH) lamp

A high-intensity discharge lamp type that uses mercury and several halide additives as light-producing elements. Metal halide lamps have better color properties than other HID lamp types because the different additives produce more visible wavelengths, resulting in a more complete spectrum. Metal halide lamps are available with CCTs from 2300 to 5400 K and with CRI values from 60 to 93. Efficacies of metal halide lamps typically range from 75 to 125 LPW.

Metamers

Lights of the same color but of different spectral power distribution.

Miniature bi-pin

A type of connector commonly used on T-5 lamps. Similar in design to but smaller than medium bi-pin connectors, it uses two small pins that protrude from the lamp ends and are inserted into a fixture socket.

Minimal erythema dose (MED)

The quantity of ultraviolet radiation (expressed in Joules per square meter) required to produce the first perceptible, redness reaction on human skin with clearly defined borders. MED can vary significantly depending on factors such as skin pigmentation.

Minimum ambient temperature

The minimum temperature at which a compact fluorescent lamp (CFL) product is warranted to start.

Minimum dimmed level

The lowest dimmed level achieved by a ballast, expressed as a percentage of that ballast's maximum light output.

Minimum load requirement

The minimum power required for an occupancy sensor to operate properly.

Minimum required efficacy

The minimum lamp efficacy required by EPACT, expressed in lumens per watt (LPW).

Minimum starting temperature

The minimum ambient temperature at which a ballast will reliably start fluorescent lamps.

Monochromatic

For light, consisting of a single wavelength and having a very saturated color.

Multitap

A passive distribution component composed of a directional coupler and a splitter with two or more output connections.

Nadir

In the lighting discipline, nadir is the angle pointing directly downward from the luminaire, or 0°. Nadir is opposite the zenith.

Noncutoff luminaire

IESNA classification that describes a luminaire light distribution in which there is no candela limitation in the zone above maximum candela. (See also cutoff classification and cutoff angle.)

Open-circuit voltage

The voltage applied across the output terminals of a ballast when no load is connected. Open-circuit voltage is the voltage applied across a lamp circuit to start the lamp. After starting, the voltage rapidly decreases and stabilizes at the operating voltage.

Operating cycle

The frequency with which lamps are cycled on and off.

Operating electrode voltage

The voltage that a ballast supplies to a lamp's electrodes.

Operating position

The manufacturer-recommended operating position for a lamp.

Operating voltage

The voltage a ballast supplies to a lamp's electrodes.

PAR lamp

An incandescent or tungsten-halogen incandescent lamp with a hard glass bulb and an interior reflecting surface, a precisely placed filament, and a lens to control beam spread. The lens is hermetically sealed to the reflector. Metal halide PAR-lamps are also now available.

Pendant mounting

A suspension device between a mount and a luminaire.

Phase displacement

The extent to which voltage and current waveforms are out of synchronous phase with one another. Current lags or leads voltage, depending on whether the current waveform crosses a reference point after or before the voltage waveform, respectively. Phase displacement can be expressed as a unit of time, as a fraction of the period, or as an angle in degrees with one period corresponding to 360 degrees. When voltage and current are synchronized, phase displacement is zero.

Phosphors

The white, powdered material coating the inside of the glass tube of a lamp. The phosphors fluoresce (emit visible light) when excited by the ultraviolet radiation produced by the mercury vapor that is energized by the electric arc sustained inside the lamp.

Photo sensor

A device used to integrate an electric lighting system with a daylighting system so lights operate only when daylighting is insufficient.

Photopic

Vision mediated essentially or exclusively by the cones. It is generally associated with adaptation to a luminance of at least 3.4 cd/m².

PN junction

For light emitting diodes, the portion of the device where positive and negative charges combine to produce light.

Polarized light

Light whose vibrations are oriented in (or around, for partially polarized light) a specific plane.

Position factor

The light output of the lamp in a certain position divided by the light output of the lamp in the base-up position.

Positive Affect

Relatively mild shifts in current mood in a positive direction.

Power

The power (in watts) used by a device to produce useful work (also called input power or active power). In lighting, it is the system input power (in watts) for a lamp and ballast combination. When referred to as benchtop active power, the measurement procedure follows ANSI standards, which include horizontally mounted bare lamp(s) at an ambient temperature of 25°C, ±1°C, and air movement less than 5 feet per minute. The lamps are seasoned 100 hours before testing, and the measurements are conducted after lamp light output stabilizes.

Power factor (PF)

The ratio of active power (in watts) to apparent power (in rms volt-amperes), power factor is a measure of how effectively an electric load converts power into useful work. Power factor (PF) is calculated using the equation PF = (active power) / [(rms voltage) x (rms current)]. Phase displacement and current distortion both reduce power factor. A power factor of 0.9 or greater indicates a high power factor ballast.

Power line carrier (PLC)

A system that transmits high-frequency (50 to 500 kHz) analog or digital signals via the power lines of a building. These signals control devices such as luminaires or contain voice transmissions such as intercom messages. Some commercial and residential energy management systems also use power line carrier systems.

Power quality

The degree to which current and voltage wave forms conform to a sinusoidal shape and are in synchronous phase with each other. Poor power quality results when the wave forms are distorted and/or out of phase and can interfere with data communications, cause inefficient operation or failure of other electrical equipment on the same supply line, and result in excessive current in electrical distribution lines.

Power reduction efficiency factor

A measure of the efficiency of a power reducer, representing the reduced light output in percent from a lighting-circuit power reducer divided by the reduced active power in percent from a lighting circuit power reducer.

Preheat

A method of starting fluorescent lamps in which the electrodes are heated before a switch opens to allow a starting voltage to be applied across the lamp. With preheat starting, the lamp flashes on and off for a few seconds before staying lit because several starting attempts may be necessary to establish the electric arc across the lamp electrodes. Often, the luminaire's start button must be held down until the lamp lights. Preheat ballasts are less energy efficient than rapid-start or instant-start ballasts.

Preheat time

For rapid-start lamps, the time from the onset of lamp current to the lamp arc's striking, during which the lamp electrodes are heated to ease starting.

Preheating time

Also referred to as preheat time and lamp preheat time. The length of time that a ballast heats a lamp's electrodes before initiating the lamp arc. Rapid start ballasts preheat a lamp before initiating the arc in order to ease starting. Too short or too l

Primary

Any one of three lights in terms of which a color is specified by giving the amount of each required to match it by additive combination.

Prismatic lens

An optical component of a luminaire that is used to distribute the emitted light. It is usually a sheet of plastic with a pattern of pyramid-shaped refracting prisms on one side. Most ceiling-mounted luminaires in commercial buildings use prismatic lenses.

Programmed start

Refers to a type of rapid start ballast that optimizes the starting process by waiting until the lamp's electrodes have been heated to apply the starting voltage, thus easing the load to the electrode and extending lamp life. Standard rapid start ballasts heat the electrodes during the starting process to allow quicker starting without flicker.

Pulse width modulation

Operating a light source by very rapidly (faster than can be detected visually) switching it on and off; the frequency and the duty cycle (percentage of time the source is switched on) are important parameters in the modulation.