초록 ▼

A pump control system which can distinguish between water and oil so that a pump can be controlled to pump water and deactivated before oil is pumped. Sensing is accomplished by a pair of capacitive sensors, one located above the other in a vessel in which water accumulates. A dual mode frequency os

A pump control system which can distinguish between water and oil so that a pump can be controlled to pump water and deactivated before oil is pumped. Sensing is accomplished by a pair of capacitive sensors, one located above the other in a vessel in which water accumulates. A dual mode frequency oscillator is associated with each sensor. Each sensor reacts to the dielectric constant of the liquid at the sensor by changing its capacitance, to thus detect the presence of a conductive substance, such as a liquid, to cause the sensor's oscillator to switch its mode of oscillation. The dual mode oscillator of each sensor selectively generates a control signal having two different duty cycles. As the dielectric constant of the liquid medium is sensed, a logic circuit interposed between the sensors allows the output of each sensor to be turned off when only the lower sensor is in water. The circuit turns on the pump only when both sensors are in water and the pump remains on until both sensors are out of water. An adjustable deadband is provided, thereby avoiding having the pump turning on and off with a slight water level change. Each sensor detects the difference between dielectric constants of air and of oil, in relation to that of water. As a result, the pump control system differentiates between water and oil and activates the system to pump water while deactivating the system before oil on the water surface is pumped.

대표청구항 ▼

[ What is claimed is:] [1.] In an underground vault of the type having air therewithin and having a sump for the accumulation of water and oil distributed over the surface of the accumulated water and where said air, oil and water each possesses a dielectric constant, said vault having also a pump h

[ What is claimed is:] [1.] In an underground vault of the type having air therewithin and having a sump for the accumulation of water and oil distributed over the surface of the accumulated water and where said air, oil and water each possesses a dielectric constant, said vault having also a pump having a motor responsive to an electrical control signal, for removing water from said sump, a system for controlling the level of water in said vault, comprising:first and second sensing means disposed in said sump in a spaced apart relationship for sensing the presence and absence of water in the space between said first and second sensing means by reacting to the differences in the dielectric constants of air, oil and water; anda logic circuit in electrical connection with said first sensing means and with said second sensing means and having an output for providing said electrical control signal to said pump, said electrical control signal having a first logic level turning on said pump signal when said first sensing means and said second sensing means react to the dielectric constant of water in said space and having a second logic level, turning off said pump, when said second sensing means reacts to the dielectric constant of air in said space and said first sensing means reacts to the dielectric constant of the oil on the surface of the water whereby substantially all of the water is removed from said vault while the oil is retained in said vault.