Fluorescent lamps are high-efficiency lamps that use electrical discharge through low-pressure mercury vapor to produce ultraviolet (UV) energy, which is then transformed into visible light. The UV excites phosphor materials applied as a thin layer on the inside of a glass tube, which makes up the structure of the lamp. The phosphors transform the UV to visible light.

With fluorescent lamps, the wavelength of the emitted light is a function of the amount of energy that is released. As a rule, fluorescent lamps convert electricity to light with greater energy than incandescent lamps. They also work at cooler temperatures. Unlike incandescent lamps, fluorescent lamps cannot be connected directly to electric lines. Instead, fluorescent lamps require ballasts to stabilize the flow of current. Fluorescent ballast provides the starting voltage and limits the amount of current that can pass through the fluorescent lamp.

How a fluorescent light works - schematic animation Video Credit: EdisonTechCenter

Specifications

Performance specifications for fluorescent lamps include rated average life, lamp power, initial lumens, mean lumens, color rendering index and color temperature.

Rated average life is the lamp-burning hours to median life expectancy.

Lamp power is the wattage of the lamp. Initial lumens is the initial light output.

Mean lumens is the average lamp output over a designated amount of time, usually 40 to 50 % of rated lamp life. A lumen is the standard international (SI) unit of luminous flux or quantity of light.

Color rendering index is an indication of a lamp's ability to render object colors in a normal, natural way. A higher number indicates better color appearance. Numbers range from 0 to 100.

Color temperature is a measure of the visual "warmth" or "coolness" of the light from the lamp. The higher the value, the whiter or "cooler" the light appears.

Base Types

Fluorescent lamps uses many different types of lamp bases: single-pin T-6, single-pin T-8, single- pin T-12, bi-pin T-5, bi-pin T-8, bi-pin T-10, bi-pin T-12, and 4-pin (circline). Recessed double-contact T-8 and recessed double-contact T-12 lamp bases are also available.

• Single-pin T-6 uses a small, single-pin connection.
• Single-pin T-8 uses a medium-sized, single-pin connection.
• Single-pin T12 uses a large, single-pin connection.
• Bi-pin T5 uses a miniature-sized, two-pin connection.
• Bi-pin T8 uses a small, two-pin connection.
• Bi-pin T-10 uses a medium-sized, two-pin connection.
• Bi-pin T-12 uses a large, two pin connection.
• Circline is a four-pin connection.
• Recessed double-contact T8 uses a small, recessed, two-pin connection.
• Recessed double-contact T-12 uses a large, two-pin connection.

Standards

ANSI C78.375 - Fluorescent lamps - guide for electrical measurements

ANSI C82.13 - Definitions - for fluorescent lamps and ballasts

IEC 61195 - Double-capped fluorescent lamps - safety specifications

IEC 61199 - Single-capped fluorescent lamps - safety specifications

Image credit:

USHIO America, Inc.