Acoustic Resonance:
Occurs when the electrical current to the lamp is unstable causing luminous fluctuation. Can lead to damage or breaking of the arc tube.

Air-cooled Reflector:
An HID light reflector with an exhaust hole on either side to allow air to flow through the reflector and cool the lamp.

Alternating Current (AC):
An electric current that reverses its direction at regularly recurring intervals; flow of electric charge that periodically reverses.

Available light in an environment before additional light is added.

Ampere (Amp):
A unit to quantify the intensity of electric current flow. Commonly referred to as Amps (A) or current (I).

Amperes (Amps):

ANSI (American National Standards Institute):
A non-profit accredited standards organization established to administer a voluntary industry standards process in the United States.

Arc Tube:
The inner tube of a high intensity discharge (HID) lamp, that contains an electric arc which produces light when an electric current passed through the tube.

ASABE (American Society of Agricultural and Biological Engineers):
An educational and scientific organization dedicated to the advancement of engineering applicable to agricultural, food, and biological systems / an international professional society devoted to agricultural and biological engineering.

Average PPFD:
Number that represents the average of all data points measured from a light fixture. It is needed to understand the overall performance of the product. Calculation = total PPFD ÷ number of PPFD measurements taken.

Shows the variance between the overall average PPFD and the minimum PPFD. The measurement is displayed as #/1. Calculation = average PPFD ÷ minimum PPFD

Average Rated Life:
The life value assigned to a particular lamp type. Statistically, Average Rated Life is a numeric value in hours of the median, (50% point), of a population of lamps that remain operating. For Example, if a lamp had an Average Rated Life of 10,000 hours and 100 new lamps were installed in the same location, approximately 50 lamps would still be operating after 10,000 hours.

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A device that, by means of resistance, inductance, capacitance, or electronic elements, singly or in combination, controls the current, voltage and waveform to the required values for proper lamp starting and operation. Capacitors for power factor correction and capacitor discharge resistors may form part of such ballast.

Ballast Factor (BF):
Measure of light output from lamp operated by commercial ballast, as compared to a laboratory standard reference ballast. BF = Lumens (Commercial Ballast) / Lumens (Reference Ballast)

Ballast Losses:
The power consumed by the ballast when it is operating a lamp. The ballast loss is calculated by subtracting the input power from the lamp power.

Ballast Noise “Hum”:
Sound made by operating Core & Coil assemblies in both electromagnetic and electronic ballasts, generated by the vibration of laminations in the electromagnetic field that transforms the voltage and current used by discharge lamps. The sound made by high frequency electronic ballasts is lower, and any noise made by models with electronic power factor connection circuits is inaudible.

A mechanical device that supports the lamp and may provide an electrical connection to operate the lamp.

A dual pin base for lamps found on CMH lamps for horticulture use. Bi-pin lamps can only be used in bi-pin sockets.

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Device in ballast that stores electrical energy.

CCF (Current Crest Factor, Lamp):
The peak lamp current, divided by the RMS lamp current. Low crest factors are important for achieving rated lamp life. CCF = Peak Lamp Current (Amps) / RMS Lamp Current (Amps)

Centigrade (C):
Celsius temperature scale where 0°C = 32°F and 100°C = 212°F.

Simple term for LED diodes ranging in different sizes and efficacy.

The mix of chemicals to create the spectrum of an HID lamp. The chemicals are housed in the arc tube of the lamp and create light when heated to extreme temperatures.

The dominant or complimentary wavelengths (colors) and purity aspects of the colors taken together.

Ceramic High Pressure Sodium (CHPS) Lamp:
A type of high pressure sodium lamp that produces a heavy red spectrum for quality flower growth.

Ceramic Metal Halide (CMH) Lamp:
A type of Metal Halide grow lamp that produces a full spectrum, typically used for veg growth but can also be used for start-to-finish growth.

Closed Fixture:
A type of reflector that houses a piece of glass on its edge encasing the grow lamp inside.

COB (chip-on-board):
Chip on board (COB) is the method of manufacturing where integrated circuits are wired and bonded directly to a printed circuit board.

Color Shift:
The change in a lamp’s color appearance, over life, measured in Kelvin compared to the initial color temperature rating.

Compact Fluorescent:
A tightly coiled fluorescent bulb designed to fit into a standard household light fixture, not typically used in growing plants.

Component of electromagnetic ballast that is surrounded by the coil and comprised of steel laminations or solid ferrite material.

Core & Coil Ballast:
Another term for electromagnetic ballast.

Correlated Color Temperature:
A specification of the color appearance of a lamp relating its color to that of a reference source heated to a particular temperature, measured in degrees Kelvin (K).

Cost of Light:
The total cost of owning a lighting system, which includes fixture, lamp, installation, maintenance labor, and electrical power costs.

Coverage Area:
Specified area a light source is intended to cover.

CRI (Color Rendering Index):
An international system used to rate a lamp’s ability to render object colors. The higher the CRI (based upon a 0-100 scale), the better colors appear. CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are also rated for the same chromaticity. CRI differences among lamps are not usually significant (visible to the eye) unless the difference is more than 3-5 points.

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Direct Current (DC):
An electric current flowing in one direction only and substantially constant in value.

DLC (Design Lights Consortium):
A non-profit organization dedicated to accelerating the widespread adoption of high-performing commercial lighting solutions; a partner of local energy efficiency groups and utility companies; sets standards for fixtures be considered for rebate incentives from member programs throughout North America.

DLI (Daily Light Integral):
The amount of Photosynthetic Active Radiation (PAR) photons accumulated in a square meter each day.

Controls the amount of power provided to an LED.

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The measure of a lamp or lighting system to convert electrical energy to radiant luminous energy. Lighting efficacy is expressed in Lumens Per Watt (LPW).

Electromagnetic Interference (EMI):
Electrical interference (noise) generated by electrical and electronic devices. Levels generated by high frequency electronic devices are subject to regulation by the Federal Communications Commission (FCC). Two classifications exist; Non- Consumer (also referred to as Class A or Commercial) and Consumer (also referred to as Class B or Residential).

Electromagnetic Radiation:
Radiation originating in a varying electromagnetic field, such as visible light, radio waves, x-rays, and gamma rays.

Electronic Ballast:
A type of ballast that uses electronic components to provide the open circuit voltage and current regulation to start and sustain a discharge a lamp.

Enclosed Fixture:
A luminaire designed to contain any hot quartz fragments that might result from an arc tube rupture.

EN lamps are Environmental Protection Agency/TCLP compliant as non hazardous waste in that they are completely lead free and contain reduced mercury.

A nationally recognized certification program by Intertek to test and certify products to specific quality and safety standards.

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The part of the spectrum with wavelengths between 700-800nm that falls between the red and infrared regions of the spectrum with benefits for flowering.

FCC (Federal Communications Commission):
The U.S. federal agency that is charged with regulating electrical interference emissions of the electromagnetic spectrum. The regulation entitled, “Part 18” deals with electromagnetic interference (EMI) from all lighting devices operating at frequencies higher than 9 kilohertz (kHz).

Fixture Requirement:
An ANSI containment classification of luminaires for specific HID lamp types. The classification code consists of the letters “O” for open, “E” for enclosed and “S” for open luminaires with lamp operating position restrictions.

Flower Spectrum:
A spectral distribution that is stronger in the red range in order to induce flowering.

A light source producing light when electricity flows through a tube that is filled with a type of gas.

Footcandle (fc):
A unit of illuminance equal to 1 lumen per square foot or 10.76 lux.

Rate of alteration in an AC current. Expressed in cycles per second or Hertz (Hz).

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Chemicals added to a lamp that neutralizes contaminants such as hydrogen and oxygen, which negatively affect lamp starting and life.

Grow Lamp:
A type of HID or fluorescent light that was made specifically for growing plants.

Grow Light System:
A type of light fixture that was designed specifically for horticulture use. HID systems include a ballast, reflector and grow lamp. LED systems include multiple LEDs, a driver, a heat sink and may include a reflector.

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Hard Glass:
Heat resistant glass that prevents breaking from thermal shock when struck by water. Borosilicate is one type of hard glass used for lamp outer jackets.

Harmonic Distortion:
A measurement of the magnitude of voltage and current harmonics as compared with the amplitude of the fundamental frequency. Harmonic distortion can be generated by a load and fed back into the AC mains, causing distortion of the sinusoidal waveform.

Refers to components of the overall frequency, an integral multiple of the fundamental sine wave frequency.

Heat Sink:
Absorbs heat from LEDs and spreads the heat out over a large area to dissipate into the air.

Height Above Canopy:
This number represents how high the fixture was when measurements were taken. The height above the canopy directly impacts all intensity measurements and the overall system performance.

Hertz (Hz):
Unit used to measure frequency of alteration of electric current or voltage per unit time. Formerly CPS (Cycles Per Second) 1CPS = 1 Hz.

HID (High Intensity Discharge):
An electric discharge lamp in which the light-producing arc is stabilized by the bulb wall temperature and the bulb wall loading is in excess of three watts per square centimeter. High intensity discharge lamp includes groups of lamps commonly known as Mercury, Metal Halide, and High Pressure Sodium.

High Pressure Sodium (HPS) Lamp:
A high intensity discharge (HID) light source which produces light by an electrical discharge between one electrode and another using sodium and mercury vapor operating at relatively high pressures and temperatures. The arc tube is made of  Polycrystalline Alumina (PCA) and is typically long and skinny. This lamp type emits an orange colored light and is used for fruiting and flowering.

High-Power LED:
3-5W – must be mounted to a circuit board.

See Reflector

Hot Restart Time:
The time it takes a HID lamp to restart and reach 90% of its light output after going from on to off to on. Typical restart times are 1 to 2 minutes for High Pressure Sodium and 5 to 20 minutes for Metal Halide.

Hot spot:
The brightest or “hottest” spot that a light source illuminates.

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IEC (International Electro-technical Committee):
An international independent standards organization. IEC standards are almost exclusively used in Europe and are adopted by many countries as their national standards for product safety and performance.

IES (Illuminating Engineering Society):
A group that seeks to “improve the lighted environment by bringing together those with lighting knowledge and by translating that knowledge into actions that benefit the public.”

Ignitor (Starter):
A device used within the ballast circuit to generate high voltage electrical pulses needed to start High Pressure Sodium and some Metal Halide lamps.

An electrical lamp in which a filament gives off light when heated to incandescence by an electric current.

Ingress Protection Rating (IP Rating):
A global ratings system used to describe how well a product is protected against intrusion of substances like water and dust.

Initial Lumens:
The measure of the amount of light a lamp produces after it has been operating 100 hours.

Input Voltage:
Voltage provided by a power line or power supply to the ballast or driver.

Input Watts:
Total power consumed by lamp and ballast when the lamp is operated at rated wattage.

Integrating Sphere:
A spherical shell used to determine total luminous flux by means of photometric measurement of a spot of light through an aperture in the shell whose white interior produces thorough diffusion of light from a source placed at its center.

How much light is being provided to the intended source.

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The unit of measure used to designate the color temperature of a light source.

Kilohertz (kHz):
One thousand Hertz (cycles per second).

Kilowatt Hour (kWh):
The standard of measure of electrical energy and the typical billing unit used by electrical utilities for electricity.

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Lamp Degradation:
The process of a lamp losing its initial output, such as lumens or spectral output.

LCL (Light Center Length):
The distance from the light center to a specified reference point on the lamp.

LED (Light Emitting Diode):
A semiconductor diode that emits light when a voltage is applied to it. The only light producing component on an LED system.

Radiant energy which can be sensed or seen by the human eye. Visible light is measured in lumens.

Light Bleaching:
What happens to plants when grow lights are placed too close to the plants causing them to receive too much light and begin to turn yellow.

Light Burn:
When plants receive too much light causing the plant to yellow, the leaf edges to turn up and brown. The leaves closest to the light source will show light burn before the rest of the plant.

Light Uniformity:
Refers to the light fixture’s ability to provide even light distribution over your plant canopy.

Lighting Layout:
A plan for where to position grow lights in a room or space most often describing their location, overall intensity levels and electrical requirements.

Long Day Plants:
A plant that flowers only after being exposed to light periods longer than a certain critical length, such as in summer. Some examples include hibiscus, lettuce, hemp, and potatoes.

LPW (Lumens Per Watt):
See Efficacy

Lumen (lm):
SI unit of luminous flux emitted within a unit solid angle (1 steridian) by a point source of having a uniform luminous intensity of 1 candela.

Lumen Depreciation:
The decrease in lumen output of a light source over time. Also called Lumen Maintenance.

A complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light, to position and protect the lamps and to connect the lamps to the power supply.

Lux (lx):
The SI unit of illuminance. One lux equals one lumen per square meter.

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Shows the variance between the maximum and minimum PPFD. The measurement is displayed as #/1. Calculation = maximum PPFD ÷ minimum PPFD.

Maximum PPFD:
Number of the maximum PPFD measurement under a light fixture. Only represents one data point under the entire light fixture. It provides the highest intensity spot and can be misleading if used alone.

McCree Curve:
Represents the average photosynthetic response of plants to light energy. It begins at 360nm and extends to 760nm. This curve can be placed over a spectral distribution chart to see how well a light source can affect plant growth.

Mean Lumens:
The average light output of a lamp over its life, usually determined by the light output at 40% of rated life.

Measured Footprint:
The area where the uniformity measurements are taken. Knowing the measured footprint will provide a better understanding of the performance throughout the total canopy.

Metal Halide Lamp:
A high intensity discharge (HID) light source which produces light by an electrical discharge between one electrode and another using a gaseous mixture of vaporized mercury and metal halides. The arc tube is made of quartz and is typically short and stout. This lamp type emits a cooler colored light and is used for early and veg stages of plant growth, but can be used in flower growth.

A unit of measurement defined as 10-6 (one-millionth) of a mole. The symbol for micromole is “µmol”

Mid-Power LED:
<1W – must be mounted to a circuit board.

Minimum PPFD:
Number of the minimum PPFD measurement under a light fixture. Only represents one data point under the entire light fixture. It provides the lowest intensity spot and is needed to calculate uniformity performance.

Mogul Base:
A large Edison Screw Base whose diameter is approximately 1.5 inches.

MOL (Maximum Overall Length):
The largest outside dimension of a lamp. Typically MOL is measured from the end of the lamp base to the top of the outer jacket.

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One billionth of a meter. The unit of measurement used for a light spectrum.

NEC (National Electric Code®):
A collection of electrical wiring specifications and standards developed by the National Fire Protection Association (NFPA), and adopted and used in all 50 states in the USA. This standard is accredited by ANSI and CSA.

NEMA (National Electrical Manufacturers Association):
The largest trade organization of electrical equipment manufacturers that publishes standards for items such as electrical enclosures, plugs and receptacles.

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Open Circuit Voltage (OCV):
Voltage, as measured at the lamp socket (HID or CFL) or across the lamp holders (fluorescent) when the lamp is not present, generated by the ballast needed to start a lamp when power is turned on.

Open Fixture:
A type of reflector that is open on its edge exposing the grow lamp inside to the environment.

Operating Position:
The specific physical orientation in which lamps are designed to operate. (for example, Base Up = BU, Base Up or Down=BUD, Base Up to Horizontal=BUH, Base Down = BD, Horizontal = HOR, etc.)

Shape LED light into the desired pattern for precise control.

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PAR (Photosynthetic Active Radiation):
A total count of light energy (in photons) between 400nm to 700nm derived from the McCree curve.

Parabolic Reflector:
A type of reflector with a circular, dome-like shape (known as a circular paraboloid) and a mirrored surface on its bottom side to reflect light.

PBAR (Photobiological Active Radiation):
A range of light energy beyond and including PAR to also include far-red and UV light.

PBFD (Photobiological Photon Flux Density):
The amount of micromoles measured within the PBAR range over a specific area; expressed as µmol/m2-s.

PCB (printed circuit board):
A circuit for an electronic apparatus made by depositing conductive material in continuous paths from terminal to terminal on an insulating surface/board.

A particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass.

Photon Flux (PF):
The number of photons per second per unit area.

A plant’s response to a recurring cycle of light and dark periods of constant length.

Formation of carbohydrates from carbon dioxide and a source of hydrogen (such as water) in the chlorophyll-containing cells (as of green plants) exposed to light.

Photosynthetic Response:
The rate at which a plant conducts photosynthesis.

The role light plays in the morphology of plants.

The gravitation of a plant toward a light source.

Phytochrome Far-Red (Pfr):
Photoreceptors in plants that absorb far-red light energy and then convert them to red energy in the presence of light.

Phytochrome Red (Pf):
Photoreceptors in plants that absorb red light energy and then convert them to far-red energy in the absence of light.

Compound used to completely surround and cover components of some magnetic and electronic ballasts in order to protect components, dampen sound, and dissipate heat.

Power Factor (PF):
The ratio of real power (watts) to apparent power VA (volts x amps). HID ballast power factor is classified in two categories, High (Pf ≥0.90), and Normal or Low, (Pf <0.90).

PPE (Photosynthetic Photon Efficacy):
How well the fixture converts energy into PAR photons. PPE is measured in µmol/J. Calculation = PPF ÷ Input Power

PPF (Photosynthetic Photon Flux):
The amount of micromoles measured within the PAR range; expressed as µmol/s.

PPFD (Photosynthetic Photon Flux Density):
The amount of micromoles measured within the PAR range over a specific area; expressed as µmol/m2-s.

Probe Start:
Method of starting Mercury vapor and specific Metal Halide lamps in which an additional electrode at one end of the arc tube assists in lamps starting.

Pulse Start:
Method of starting High Pressure Sodium and specific Metal Halide lamps in which a high voltage starting pulse starts the lamps.

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A high heat resistant glass-like material manufactured from pure silica sand. Quartz is used for the arc tube in Mercury and many Metal Halide lamp types.

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Rated Life:
See Average Rated Life

Reduced Jacket:
A reduction in lamp bulb outer jacket size from the traditional standard size. Reduced jacket lamps are designed for special fixture applications and have generally shorter rated life.

A polished surface for reflecting light, usually a metal such as aluminum.

RFI (Radio Frequency Interference):
Form of electromagnetic interference.

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Seasoning Time:
The time required for a new operating lamp to reach a state of equilibrium where the electrical, light level and color parameters stabilize. Typically, HID lamps obtain their rated performance after 100 hours of seasoning.

Short Day Plants:
A plant that can flower after being exposed to light periods shortern than a certain critical length, such as in winter. Some examples include pointsettias and chrysanthemums.

SI Unit:
The International System of Units universally abbreviated SI (from the French Le Systeme d’Unites).

An opening or holder for an HID light source that facilitates an electrical current to the lamp.

A linear representation of the different radiant electromagnet wavelengths ranging from cosmic rays to radio waves.

Spectrum Degradation:
When chemical reactions within the arc tube (which create the light and spectrum) deteriorate over time.

System Efficacy:
Overall efficiency of the lamp/ballast system. System efficacy = total lamp lumens / system wattage.

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T12, T10, T8, T5:
Industry standard naming for a fluorescent lamp. (T = Tubular and the numbers that follow represent the diameter in 1/8 inch increments).

Thermal Management:
A fixture’s ability to dissipate heat.

Thermal Protector:
A self resetting switch that disconnects power to the ballast if internal temperatures rise above the trip point – typically 105°C

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UL (Underwriters Laboratories):
Underwriters Laboratories Inc. is an independent, not-for-profit product safety testing and certification organization. UL has tested products for public safety for more than a century.

UV (Ultraviolet):
Radiant energy within the wavelengths of 100-400nm. UV energy is classified by IEC in three categories: UVA – 315 to 400 nm (“Black Light”), UVB – 280 to 315 nm (Bacterial Sterilization) and UVC – 100 to 280 nm (Ozone Producing).

Ultra Ace™ EN:
Converts a Mercury or Metal Halide system to High Pressure Sodium by simply changing the lamp. Meets Federal EPA TCLP requirements for non-hazardous waste.

Symbol for the micromole, a unit of measurement.

How consistent the product emits light across the plant canopy or surface below.

Uniformity Ratios:
A ratio describing the a light’s ability to project consistently over a specified coverage area. A perfectly uniform light will have a ratio of 1/1. The closer these ratios are to 1, the more uniform the product lights the canopy. Ratios include Max/min and Avg/Min and are obtained by using the PPFD or PBFD within the coverage area.

Universal Operating Base Position:
Lamps that can be installed and operated in any position. The letter U commonly designates universal position operating lamps.

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Veg Spectrum (aka Growth Spectrum):
A spectral distribution that is stronger in the blue range in order to induce strong growth before flowering.

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Warm Up Time:
The time from the initial establishment of an arc to 90% of the steady state full light output of the lamp.

Watt (W):
A unit of power used to quantify the rate of doing work. In electrical calculations, one watt is the power produced by a current of 1 ampere across a potential difference of one volt. In addition, the radiant luminous flux of a lamp is also expressed in watts.

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