Integrated measuring apparatus for measuring vapor pressure and liquid level of liquid tank

A liquid tank comprising:

• a tank configured to contain a liquid;
• vapor (or vaporized gas) pressure tube configured to comprise one end connected to an upper part of the tank;
• a liquid pressure tube configured to comprise one end connected to a lower part of the tank;
• a pressure sensor configured to sequentially measure vapor pressure and total pressure, or a combination of vapor pressure and liquid pressure;
• and
• a switching valve configured to switch communication paths between the vapor (or vaporized gas) pressure tube or the liquid pressure tube and at least one of first and second input ports of the pressure sensor.

An integrated measuring method for measuring liquid level and vapor pressure of a liquid contained in a tank, using an integrated measuring apparatus comprising one pressure sensor and a switching valve to switch a path at an input port of the pressure sensor, the method comprising:

• measuring vapor pressure at a top surface of a liquid in a tank by controlling a path of the switching valve;
• outputting a vapor-pressure-indicating signal;
• measuring a differential pressure by controlling the path of the switching valve, wherein the differential pressure is a difference between the vapor pressure and a total pressure at a lower surface of the tank;
• and
• generating a liquid-level-indicating signal from the differential pressure and outputting the generated signal.

An integrated measuring method for measuring liquid level and vapor pressure of a liquid contained in a tank, using an integrated measuring apparatus comprising one pressure sensor and a switching valve to switch a path at an input port of the pressure sensor, the method comprising:

• measuring liquid pressure at a top surface of a liquid in a tank by controlling a path of the switching valve;
• outputting a vapor-pressure-indicating signal;
• measuring a total pressure at a lower surface of the tank by controlling the path of the switching valve;
• and
• generating a liquid-level-indicating signal from a difference between the vapor pressure and the total pressure and outputting the signal.