Patent ID: 8272264

Claim:
A liquid level gauge for continuous measurement of a liquid level in a steam drum under all conditions, comprising: a metal measurement tube having a steam-side pipe fitted on an upper part for connecting to the steam drum, and a water-side pipe fitted on a lower part for connecting to the steam drum; an insulated jacket pipe disposed inside the metal measurement tube; a first probe disposed in the insulated jacket pipe with a first clearance to the water-side pipe to form a first capacitor between the first probe and the metal measurement tube; a second probe disposed in the insulated jacket pipe above the first probe with a second clearance to form a second capacitor between the second probe and the metal measurement tube; a third probe disposed in the insulated jacket pipe above the second probe with a third clearance to form a third capacitor between the third probe and the metal measurement tube; a transmitter having a liquid level calculation method based on capacitance values of the first, second and third capacitors, and heights of the three probes and three clearances; and first, second and third lead wires respectively connecting the first, second and third probes to the transmitter; wherein the first, second and third probes are mutually insulated and the transmitter calculates the liquid level using the liquid level calculation method through measuring respective capacitance values of the first, second and third capacitors.