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The
Flood Lamp in a Dome Reflector
Because
the beam from a flood lamp is so wide, it is often placed
in a dome reflector, which acts as a lampshade and reduces
glare from the sides of the bulb.
Zoo
Med recommend that the Powersun be placed in one of their
Clamp Lamps, the Deluxe version of which has a dome reflector
with a white porcelain interior. Inexpensive aluminium dome
reflectors and “brooder lamps”, available from several manufacturers
and farm suppliers, are also in widespread use.
We tested
a 100watt Powersun lamp in the same three fixtures in which
we tested the compact fluorescent tubes: a
polished aluminium dome, diameter 8.5ins;
a brushed aluminium farmers’ brooder
lamp fixture; and the Zoo Med
Clamp Lamp dome with a white painted porcelain interior,
diameter 8.5ins. The results are shown in Fig. 1.
The
Powersun 100watt lamp fitted deeply into the tall, brushed
aluminium brooder lamp we used. All light from the
sides of the lamp was reflected downwards, creating a much
more intense, directional beam. Output directly beneath
the lamp was increased by more than two and a half times,
at all distances over 6”.
The
bulb partially protruded from the two dome reflectors, and
only the light from the very edges was diverted downwards.
The white painted surface of the porcelain dome of the Zoo
Med Clamp Lamp dome does not reflect UVB strongly,
and there was little effect upon output.
The
reflection from the polished aluminium
dome, however, had an extremely noticeable effect
upon the readings taken at close range, but not on those
taken from further away. This may be because the polished
surface, unlike the brushed aluminium, does not diffuse
the reflected part of the beam but rather, focuses it to
a point just under the dome itself.
It seems
likely that the effects of a dome reflector would therefore
vary depending upon the relative size of the lamp, the size
of the dome, and the nature of the inside surface of the
dome. Without the assistance of a UVB meter, we consider
that it would be very difficult to estimate the output of
a lamp in a dome reflector or brooder lamp fixture.
With
a product that is apparently quite variable in output anyway,
this does make assessing the placement of a lamp in a vivarium
rather problematical.
Manufacturer’s
instructions regarding safe minimum distances should be
taken into careful consideration, as should the temperature
measured at the basking spot directly under the lamp.
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