One of the environmental parameters of a pan-tilt-zoom camera, which is difficult to test in a conventional test lab or with a home-brewed test setup, is the ability of the camera to withstand strong wind conditions without having its viewing direction influenced. Testing the ability of the camera to stay focused on target in high winds requires a visit to your local wind tunnel.
WTI took a trip to the San Diego Air & Space Technology Center to test our Sidewinder camera in their low speed wind tunnel. In the context of the aeronautical community “low speed” means below MACH 1, the speed of sound. The wind tunnel at the San Diego Air & Space Technology Center is capable of generating sustained wind speeds of up to 250MPH!
The San Diego Air & Space Technology Center is the only privately held low speed wind tunnel in the United States. Most of the testing done at the center is aeronautical in nature, and the center has been involved in the testing of such well known aircraft as the F-106, B-58, F-111, F-16, Global Hawk UAV, Tomahawk Cruise Missiles, and Advanced Cruise Missiles. More recently, the center has become a Mecca for top level cyclists and luge racers who are trying to gain every possible competitive edge, by refining their equipment and body position profiles for the least possible wind drag.
The heart of the wind tunnel is the 22,000 horsepower electric motor that drives the turbine blades. The motor is the original motor that was installed in 1947. The turbine blades have been upgraded and replaced over the years to improve the performance of the wind tunnel. The air flow is re-circulated through the oval shaped tunnel to improve the efficiency of the tunnel. The tunnel walls actually form part of the building structure itself!
Once the air has been accelerated by the electric turbine, the turbulence is removed by passing the air through a honeycomb-shaped array of tubes. The air flow is then funneled and channeled into the 8 foot tall by 12 foot wide test chamber area. This is where the testing actually takes place.
Testing is monitored through the viewports on the sides of the test chamber, since it is not a good idea to be inside the chamber when the turbine is powered up! If you were to stand inside the chamber, leaning into the wind, at about 80MPH the force of the wind would overcome the friction of your shoes on the floor and you would be swept away down the tunnel. Some adventurous TV weather broadcasters once volunteered to be tethered inside the chamber to see how much wind force they might be able to withstand while doing remote broadcasts during hurricanes. At about 120MPH facing into the air flow, it became difficult to exhale and the pummeling by the wind became very severe, resulting in the testing being stopped.
The primary result of our testing showed that it requires a wind speed of over 120MPH to overcome the holding torque of the stepper motor drive and move the camera off position with the Sidewinder camera positioned directly into the wind as shown above. We were very pleased to learn that our camera performed so well in this sort of extreme condition.
WTI performed a variety of tests in the tunnel to determine just how much wind force the Sidewinder camera was able to withstand, without the viewing angle being affected. Some of the tests were run on a specially instrumented camera, allowing us to precisely measure the torque applied to the camera components at different wind speeds and with different camera angles. The measurements that we made this day are going to help us improve the performance of the Sidewinder camera even more in the future.
All in all, it was a very fun and interesting day at the San Diego Air & Space Technology Center.
~Dale Roche, Director of Engineering
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WTI (Wireless Technology, Inc.)
Video Surveillance Products Dedicated to the Broadcast, Global Security and Transportation Markets!
www.gotowti.com ● www.wirelesstech.com
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