Lighting

• by the passage of an electric current
• through a vapor or gas, rather than through a tungsten wire as in incandescent
• lamps.

• • Light
  • production is more efficient than electric heating methods in filament lamps.

• low-pressure mercury arc discharges sources.
• an electric arc is passed between 2 cathodes, one at each end.

• mercury ionizes (vaporizes) to fill the inside of the bulb.
• This vapor strikes the tube wall and phosphors
• are excited and fluoresce or become luminous.

• • the
  • types of phosphorescent materials coated on the inside of the bulb and the
  • entire actual tube structure becomes the light source.

• • greater
  • wattage loss, more heat is developed and efficacy is lower.

hot-cathode

• -
• • These
  • are coiled tungsten filaments (cathodes) at each end of the tube and have
  • greater efficacy with lower cost for equal amounts of illumination.

• small diameter cold-cathodes lamps that can be shaped into signage and artworks. Gases are excited instead of phosphors.
• - Cold-cathode lamps have excellent starting ability and are easily dimmed.

Ballast

• Three types of mechanisms available:
• preheat: the oldest type taking a few seconds to “pre” heat the circuit using a “starter”..
• instant-start: does not require a starter which simplifies the circuitry.
• rapid-start: combines the features of pre-heat and instant start. Starters are unnecessary.

• • Dimmimg
  • fluorescent lamps was not possible until more recent development of new
  • lighting systems that rely on a balance of the appropriate starting mechanism,
  • ballast and improvements in the actual lamp.
• • Care should be
  • taken when specifying fluorescent products due to the fact that many products
  • are still available today that would not allow dimming potential.
• • When working with
  • older products in renovations if dimming is necessary the fixture should be
  • assessed for the potential to dim.

• T12 versus T8 and T5 : this involves the amount
• of glass tube used, phosphorescent materials and wattage

• During the first 100 hours of usage the
• lumen rating of most fluorescent lamps drops by 5 %. After that lumen reduction
• is less rapid which is a valued feature for efficacy.

• This is another valued attribute of
• fluorescent lamps due to the fact that a huge range of lamp life exists from
• 7,500 hours to 24,000.

• The EPACT of 1992 established minimum efficacy
• standards for fluorescent lamps. Minimum standards for production and imports
• must have a color rendering index (CRI) of 69. Lamps with CRI ratings of 82 or
• higher are exempt from these efficacy standards.

• The mercury arc in a fluorescent lamp
• operates at 60hz cycles. This means it actually turns on and off 120 times per
• second. The lamp stays visible due to the “carry-over” action of the phosphors.

CRI takes into account color rendering and the quality of light over the length of life as well as operating efficiency and assumed lamp life.

• • Produce
  • light by passing an electric current through a gas or vapor operating at high
  • voltage.

produces light using mercury vapor

• or “multi-vapor” produces light using combined
• vapors of mercury and metal halides.

• produces light using combined vapors of mercury
• and sodium with the later being the dominant color source producing an orange
• tinted color.

• • Technically
  • not HID.
  
  
  • High
  • efficacy ratings
  
  
  • Unsuitable
  • for interiors due to extremely narrow spectral range…,high in yellow
  • concentration.

• • HID
  • lamps require a ballast to regulate the arc current flow.
  
  
  • Extinction
  • of lamp service can occur due to a power interruption, a severe voltage dip or
  • insufficient voltage maintained from the ballast.

• It
• is important to note that lamp extinction can require a cooling down period
• before the arch with re-strike and create light.