he proposed solution makes use of two reservoirs, one for oil connected to the top of the cylinder, and one for water connected to the bottom. The water reservoir will have a pump attached, and it is through the action of this pump that the volumes of the two fluids will be manipulated; as the water pressure is increased, the water level in the cylinder will rise, and the oil will be forced back into the oil reservoir. When the pump is off, the fluids will be held in place with a valve; opening the valve will allow water back into the lower reservoir, and oil into the cylinder.
The cylinder will contain an array of conductive rods, whose capacitance will change when the fluid levels change. Since the dielectric coefficient of water is greater than that of oil, the capacitance will be higher when the cylinder is filled with oil than when it is filled with water. By measuring this capacitance, one will be able to determine the relative volumes of the fluids. This information will be reported to the controller PC, and used to regulate the action of the pump to set the volumes to the desired levels.
The PC will be equipped with a frequency counter / digital output card which will perform the measurements and control the pump and valve.