The Ultima Switch technology works on the principal of detecting a change in the dielectric constant of its environment. The incorpoarted sensors project a weak micro-electric field which is disrupted in the presence of water--- even very pure water.
When the field becomes disrupted, the sensor recognizes that an activation has occurred and turns on or off, depending on how it has been wired.
Petroleum products such as oil, grease, diesel fuel, gasoline, etc. have a dielectric constant well below the threshold which the sensors have been programmed to recognize, and thus do not affect the switch. This is why the Ultima Switch technology ignores these materials in the bilge and can still detect the presence of water, even if the sensors get covered with petroleum products.
Warning. This product can expose you to chemicals including Diisononyl Phthalate which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warning.ca.gov
www.P65Warnings.ca.gov