| 摘要 |
Detecting different fluids, such as oil at the surface of water, by a heated monitoring element exposed for contact with the fluid, the element having a resistance characteristic that changes as a function of temperature, in preferred embodiments being the mere filament of a light bulb. One system employs circuitry for periodically applying a pulse of electrical heating current to the monitoring element, to heat and produce a change in its electrical resistance, and output circuitry responsive to change in electrical resistance to indicate the nature of the fluid. In another system the resistance of the monitoring element is controlled by comparison to a constant reference, the heating current required serving to indicate the nature: e.g. oil, water or air, of the fluid contacting the element. Features of the invention include positioning the monitoring element at a liquid-air interface by a buoyant member, preferably with means to cause the element to transit the interface prior to a detection cycle; a driver supported on a housing, effective to move the element to produce this motion; circuitry for passing heating current through the monitoring element to clean its exposed surface of oil; and circuitry for limiting the electrical parameters of the cleaning current to prevent ignition of oil. |
