Vasilis Stasinos watches while electrical engineer Aggelos Mallios checks Thetis' electrical systems following a ground fault alarm triggered during a previous dive. Click image for larger view and image credit.
Vasilis Stasinos watches while electrical engineer Aggelos Mallios checks Thetis electrical systems following a ground fault alarm triggered during a previous dive. Click image for larger view and image credit.
Safety First
June 29, 2006
36 N, 24 E
Dr. Richard Camilli
Co-Principal Investigator
When using technology harboring human lives, safety always comes first. A pre-dive checkout is conducted on Thetis before every single dive to ensure the vehicle is working appropriately, and is safe to carry human lives. Following this morning’s pre-dive checkout, today’s Thetis dive was aborted.
During the pre-dive checkout we performed systems tests, but were unable to establish a reliable data connection between the submersible’s internal computer and the sensors. We were on pins and needles because a ground fault alarm (an early warning of potential damage to the electrical systems) had been triggered during a previous dive. Kostas, Aggelos, and Thodoros Fotopulos spent the rest of that day inspecting the submersible. The warning alarm stopped after they cleaned all of the electrical contacts and replaced a questionable electronic relay (transmitter). Today’s communications problem did not appear to be related to the previous day’s problem, but we decided to scrub the mission until we could identify where the problem was originating.
In the end the problem was just a simple radio wave interference caused by a cable from the submersible’s hydraulic systems being too close to our communications cable. This problem is comparable to what happens when a radio or television displays static from another electrical device like a kitchen blender or a vacuum cleaner. The interference disappears when the submersible is in seawater because radio waves cannot penetrate seawater. This effect, known as shielding, is very helpful for the sensors because it allows them to accurately measure faint signals, similar to the way that it is easier to hear a whisper in a quiet room than in a noisy one.
Thetis is cleared as safe for diving, and should be back in the water tomorrow.
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