| 摘要 |
Disclosed is a fluid level sensing system for sensing the level of the interface between a first fluid, e.g. water, and a second fluid, e.g. steam, the first fluid being beneath and of lower electrical impedance than the second fluid. The system comprises an electrically conductive vessel for containing the fluids and a plurality of vertically spaced sensors each of which has a sensing portion which projects into and is electrically insulated from the vessel and which is arranged, in use, to produce a signal representative of the impedance of the fluid between the sensing portion and the vessel. Output means are responsive to the impedance-representative signals for producing a first signal which is dependent upon the ratio between the impedance sensed by the sensor at or immediately below the interface and a value for the impedance of the first fluid derived from at least one sensor below the sensor at or immediately below the interface, and for combining the first signal with a second signal dependent upon the level of the sensor at or immediately below the interface so as to produce an output signal representative of the level of the interface within the vessel.
|
