Fluorescent Lamps Basics

The fluorescent lamps was the first major advance to be a commercial success in small scale lighting since the tungsten incandescent bulb. Its greatly increased efficiency resulted in cool (temperature wise) brightly lit workplaces (offices and factories) as well as home kitchens and baths. The development of the mercury vapor high intensity discharge (HID) lamp actually predates the fluorescent . However, HID type lamps have only relatively recently become popular in small sizes for task lighting in the home and office; yard and security area lighting; and light source applications in overhead, computer, and video projectors.

Fluorescent lamps are a type of gas discharge tube similar to neon signs and mercury or sodium vapor street or yard lights. A pair of electrodes, one at each end - are sealed along with a drop of mercury and some inert gases (usually argon) at very low pressure inside a glass tube. The inside of the tube is coated with a phosphor which produces visible light when excited with ultra-violet (UV) radiation. The electrodes are in the form of filaments which for preheat and rapid or warm start fixtures are heated during the starting process to decrease the voltage requirements and remain hot during normal operation as a result of the gas discharge.

When the lamp is off, the mercury/gas mixture is non-conductive. When power is first applied, a high voltage (several hundred volts) is needed to initiate the discharge. However, once this takes place, a much lower voltage - usually under 100 V for tubes under 30 watts, 100 to 175 volts for 30 watts or more - is needed to maintain it.

The electric current passing through the low pressure gases emits quite a bit of UV (but not much visible light). The gas discharge's radiation is almost entirely mercury radiation, although the gas mixture is mostly inert gas and generally around something like 1 percent mercury vapor. The internal phosphor coating very efficiently converts most of the UV to visible light. The mix of the phosphor(s) is used to tailor the light spectrum to the intended application. Thus, there are cool white, warm white, colored, and black light fluorescent (long wave UV) lamps. There are also lamps intended for medical or industrial uses with a special envelope such as quartz that passes short wave UV radiation. Some have an uncoated envelope, and emit short-wave UV mercury radiation. Others have phosphors that convert shortwave UV to medium wave UV. Fluorescent lamps are about 2 to 4 times as efficient as incandescent lamps at producing light at the wavelengths that are useful to humans. Thus, they run cooler for the same effective light output. The bulbs themselves also last a lot longer - 10,000 to 20,000 hours vs. 1000 hours for a typical incandescent. However, for certain types of ballasts, this is only achieved if the fluorescent lamp is left on for long periods of time without frequent on-off cycles.

Fluorescent Lamps Labeling
The actual fluorescent tubes are identified by several letters and numbers and will look something like 'F40CW-T12' or 'FC12-T10'. So, the typical labeling is of the form FS WWCCC-TDD (variations on this format are possible): F - Fluorescent lamp. G means Germicidal shortwave UV lamp. S - Style - no letter indicates normal straight tube; C for Circline. WW - Nominal power in Watts. 4, 5, 8, 12, 15, 20, 30, 40, etc. CCC - Color. W=White, CW=Cool white, WW=Warm white, BL/BLB=Black light, etc. T - Tubular bulb. DD - Diameter of tube in of eighths of an inch. T8 is 1", T12 is 1.5", etc. For the most common T12 (1.5 inch) tube, the wattage (except for newer energy saving types) is usually 5/6 of the length in inches. Thus, an F40-T12 tube is 48 inches long.

Specialty Fluorescent Lamp Types
All Sorts of Less Conventional Lamps
In addition to the boring white ones (OK, well 'white' does come in various colors!), other interesting types of lamps include all sorts of real colors (red, green, blue, yellow), blacklight lamps, germicidal lamps in which there is no phosphor coating at all and a quartz tube to transmit short-wave UV light (e.g., EPROM erasers and PCB photoresist activation), sunlamps, plant lights and special purpose specific wavelength lamps such as reprography and copier lamps.

Blacklight Fluorescent Lamps
There is a 350BL blacklight lamp, using a different phosphor that emits a band of slightly shorter UV wavelengths in the UV-A range. The reasoning for this lamp is that it is supposedly optimized for attracting insects. These lamps are one variety of UV lamps used in electric bug killers. There are other UV fluorescent lamps. There are at least two different UV/deep violet emitting fluorescent lamps used mainly in the graphic arts industry, emitting mainly wavelengths between 360 and 420 nanometers. Possibly one of these is also used in bug killers. I have noticed one kind of UV fluorescent lamp for bug killers with a broadish band phosphor with significant output from the 360 nanometer range (maybe also shorter) into visible wavelengths around 410 to 420 nanometers or so.

Compact Fluorescent Lamps
These are miniaturized fluorescent lamps that usually have premium phosphors which often come packaged with an integral ballast (either iron or electronic). They typically have a standard screw base that can be installed into nearly any table lamp or lighting fixture that accepts an incandescent lamp.Compact fluorescents are being heavily promoted as energy savings alternatives to incandescent lamps. They also have a much longer life - 6,000 to 20,000 hours compared to 750 to 1000 hours for a standard incandescent.

Cold Weather Fluorescent Lamps
There are special lamps with heavy glass jackets and/or with krypton gas filling for cold weather/freezer applications. They work best at below room-temperatures. It really annoys me when I go to the grocery store or see outside installations with dim, flickering tubes! What a waste of electricity!

Various kinds of fluorescent lamps types

Fluorescent lamps Nominal Length:
0, 3.4, 3.5, 4.0, 4.2, 4.3, 4.375, 4.4, 4.7, 4.8, 4.875, 4.9, 5, 5.0, 5.1, 5.2, 5.25, 5.3, 5.4, 5.5, 5.7, 5.75, 5.8, 5.9, 6, 6.0, 6.1, 6.25, 6.3, 6.4, 6.6, 6.7, 7.3, 8, 8.1, 9.0, 9, 10.5, 12, 12.8, 15, 16.5, 18, 20.7, 21, 21.6, 22, 22.5, 24, 26, 28, 30, 33, 33.4, 36, 42, 45.2, 48, 57.1, 60, 64, 72, 84, 96 ,etc

Fluorescent lamps Watts:
1-25, 26-39, 40, 41-60, 61-74, 75, 76-110, 111-300
Base: 4 PIN (Circline), Medium, Medium BiPin, Miniature BiPin, Mogul BiPin, Recessed Double Contact, Single Pin, Single End ,etc

Shade of fluorescent lamps:
Reflector (R), Biax (T), Circline (T9), T5, T6, T8, T10, T12, T17, T19, Power Groove (PG17), Two-Dimensional (2D), Bullet, Globe, A24, HLX, Other ,etc

Lamp Tone (Color Temp):
Soft White (2700), Warm White (2800), Warm White (2900), Warm White (3000), Neutral White (3500), Neutral White (3700), Cool White (4100), White (4200), Chroma 50 (5000), Sign White (5400), Daylight (6500), Chroma 75 (7500), etc

Some picture of fluorescent lamps: