Light
Ratings
Besides using the
color temperature and the Color Rendering Index we also use
a few forms of measurement:
Lumen - Measures the total
amount of visible light emitted by the light source. Visible
light is a key term since Lumens are used in applications
where the human perception of light is important, like in most
uses of the electric lamp. The human eye does not see all frequencies
of light with the same intensity, therefore when measuring lumens
you are not simply measuring the energy of all wavelengths emitted
by the light source.
The human eye happens to see the green spectrum with the most
intensity.
Lux - A measurement of amount
of light over a given area. 1 lx = 1 lumen per sq meter
Candlepower
Lumens per Watt - How well
a light source converts energy into visible light. This is very
important for measuring efficiency of a light type. Lumens per
watt (lm/W) ratings will vary even within one light type due
to materials used and slight design differences. Lumens per
Watt ratings on light packaging is almost always wrong. Companies
test products in ideal circumstances, not in the average home
or work setting. They also may not take into account inefficiencies
created by the aging of the ballast materials. The common CFL
typically never lasts the full life on the box due to electronic
ballast failure, not because of the light source failure.
Candlepower
- The older unit in which they measured the intensity of light
emitted from a source using the standard of a candle of a certain
type, size, and weight. Over the years scientific institutions
tried to make it more precise by changing the standard to a
lightbulb type and later a blackbody at the freezing point of
liquid platinum. Now we use lumens.
Candela - Another term for
rating light intensity created in 1948. 1 candela is = 0.981
candlepower.
Reliability
of a Lamp Type
Lamps
can fail due to the way it makes light or the exterior apparatus
that helps run the lamp (like a ballast). LEDs have reliability
problems in outdoor settings because of extreme temperature
variations in the environment, this is because semiconductors
in the design are sensitive to heat. Or If a cooling fan (mechanical
failure) on a large LED fails, it may result in the overheating
and destruction of the device. Neon signs may have trouble keeping
hot enough to keep the arc going in cold weather, the result
is a flickering. Fluorescent lights can be very reliable if
the ballast is build solid, however many companies today use
cheap, light materials in ballast design to save on cost and
make the product fail prematurely. This is done to sell more
lamps. If you look at early General Electric and Philips fluorescents
from the 1940s the ballasts were made with a lot of copper and
heavy materials. Many of these lamps are still in operation
today in older facilities.
Module
1 QUIZ: (print an answersheet to record your answers
here)
1.
The mercury vapor lamp is considered:
a.) an incandescent lamp
b.)
an arc discharge lamp
c.) a chemical reaction lamp
d.) semiconductor lamp
2. When the orbital returns inward it emits a _________.
a.) electron
b.) neutron
c.) neutrino
d.) photon
3.
A color temperature of 6000 Kelvin would be ________ than a
color temperature of 1000 Kelvin.
a.) more blue
b.) more red
4.
True or False: A lumen measures the full spectrum of light emitted,
both visible and not visible to the human eye.
a.) True
b.) False
5.
The Best CRI rating possible is:
a.) 1000
b.) 55.8
c.) 100
d.) 77.3
Now
that you have finished learning the basics its time
to dive into the inventions of the lamps themselves! Begin Module
2 below.
