General Description of the Basic Light
The SAI™ Basic Light has been developed as part of a system for visualizing complex airflows with neutrally-buoyant bubbles filled with helium. Like our Modulated Arc Lamp, it provides a beam of uniform intensity to illuminate the trajectories of the helium bubbles. The Basic Light accomplishes this at a fraction of the cost of the arc lamp if velocity measurements are not required. Also, the smaller, compact design allows for more flexibility and quicker diagnosis of "large-scale" airflow patterns. Overall, the Basic Light is quite simple and rugged in design, easy to use and adjust, and cool in operation. The complete assembly with a detachable tripod support weighs only 3.5 lbs. This support mounts to a full size tripod with a Quick Release Panhead.
This SAI™ Light uses a standard ELH 300W tungsten-halogen lamp, generally available from many camera supply stores. Lamp life is rated at 35 hours. Power for the lamp and cooling fan is supplied directly through a grounded, plug-in power cord and a toggle "ON-OFF" switch mounted in the bottom cover, along with a general-purpose power entry module. The projection lens and a unique aperture assembly allow focusing of the light beam on any flow from 24" to infinity. Two apertures are included with the SAI™ Universal Basic Light, an iris and an adjustable slit. The iris provides a circular beam spread that can vary from 2” – 24” in diameter at 6’, while the slit provides a rectangular beam spread from 0” by 22” to 8” by 22” at the same distance.
Two Adjustable Apertures
Both an Adjustable Slit and an Iris Aperture are included with the light. The adjustable slit provides a rectangular beam or "slab" of light varying in width. This is particularly helpful to visualize 2-D airflows or to study 2-D cross sections of a complex 3-D airflow. On the other hand, the Iris Aperture provides a round beam varying in diameter. This is really useful for examination of axisymmetric airflows or the overall exam-ination of any airflow.
To change the width of the slit in the Slit Aperture, remove it from the Cradle and loosen the four 4-40 screws that hold the two leaves in place and reset as desired. The orientation of the slit may also be adjusted by the rotation of the Aperture in the Cradle before the black Thumb Knob is tightened.
To adjust the beam diameter of the Iris, simply move the chrome lever on the side of the Iris. The Iris should be set in the Cradle so that the opening on the side of the Iris for the Iris Handle is aligned with the open notch in the Cradle.